Article

Managing Predation on Ground-Nesting Birds: The Effectiveness of Nest Exclosures

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Abstract

Ground-nesting birds have declined world-wide, probably partly due to high nest predation. A non-lethal method for decreasing predation uses protective cages at nests. Tests have mainly looked at the effect of such nest exclosures on hatching success and adult predation, but several additional aspects need to be explored for a comprehensive evaluation of this conservation technique. Here, we test the effect of nest exclosures in two common European shorebirds: northern lapwing (Vanellus vanellus) and redshank (Tringa totanus), measuring hatching success, incubation length, hatching synchrony, hatchability, partial clutch loss, chick condition, and adult predation. In both species, protected nests had higher hatching success than unprotected nests. Taking into account incubation time, nest abandonment, hatchability and partial clutch loss, protected nests still hatched more young than unprotected controls. In lapwings, but not in redshanks, protected nests were incubated longer, but this did not impair the condition of lapwing chicks. Protected redshanks suffered increased predation on incubating adults, which often sit on the nest until a predator is close by. Our results emphasize the need for caution in the use of nest exclosures, particularly in redshanks and other species with similar incubation behaviour. Exclosures can, however, be a useful management tool in shorebirds that leave their nest early, when an approaching predator is still far away.

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... A more targeted approach is to construct exclosures, such as cages and small perimeter fences, around nests that allow adults to perform parental duties while hindering access by predators. These nest-level predator exclosures can be effective at increasing reproductive success (Rimmer and Deblinger 1990, Johnson and Oring 2002, Isaksson et al. 2007). However, installing predator exclosures is intrusive and can lead to nest abandonment or adult mortality by limiting escape routes for parents (Johnson and Oring 2002, Murphy et al. 2003, Isaksson et al. 2007 or by attracting predators to nest sites (Beaulieu et al. 2014, Ferreira-Rodr ıguez andPombal 2018). ...
... These nest-level predator exclosures can be effective at increasing reproductive success (Rimmer and Deblinger 1990, Johnson and Oring 2002, Isaksson et al. 2007). However, installing predator exclosures is intrusive and can lead to nest abandonment or adult mortality by limiting escape routes for parents (Johnson and Oring 2002, Murphy et al. 2003, Isaksson et al. 2007 or by attracting predators to nest sites (Beaulieu et al. 2014, Ferreira-Rodr ıguez andPombal 2018). These impacts can counteract potential increases in reproductive success (Mabee and Estelle 2000, Johnson and Oring 2002, Pearson et al. 2012. ...
... Widespread use of exclosures for predation management is challenging because their effectiveness depends on species-specific responses to disturbance or flushing behavior (Isaksson et al. 2007). Effectiveness also may vary within a species depending on local habitat features and predation pressures (Mabee and Estelle 2000, Johnson and Oring 2002, Cohen et al. 2016, Kwon et al. 2018. ...
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en Increasing nest survival by excluding predators is a goal of many bird conservation programs. However, new exclosure projects should be carefully evaluated to assess the potential risks of disturbance. We tested the effectiveness of predator exclosure fences (hereafter, fences) for nests of critically endangered Florida Grasshopper Sparrows (Ammodramus savannarum floridanus) at a dry prairie site (Three Lakes; 2015–2018) and a pasture site (the Ranch; 2015–2016) in Osceola County, Florida, USA. We installed fences at nests an average of 8 days after the start of incubation, and nest abandonment after fence installation was rare (2 of 149 installations). Predation was the leading cause of failure for unfenced nests at both sites (48–73%). At Three Lakes, nest cameras revealed that mammals and snakes were responsible for 61.5% and 38.5% of predation events, respectively, at unfenced nests. Fences reduced the daily probability of predation (0.016 for fenced nests vs. 0.074 for unfenced nests). The probability that a fenced nest would survive from discovery to fledging was more than double that of unfenced nests (60.4% vs. 27.7%). However, we found no difference in daily nest survival at the Ranch between the year before nests were fenced (2015; 0.874) and the year when all but one nest were fenced (2016; 0.867) because red imported fire ants (Solenopsis invicta) were responsible for 86% of predation events at fenced nests at the Ranch. The use of cameras at fenced nests revealed that site‐specific differences in nest predators explained variation in fence efficiency between sites. Our fence design may be useful for other species of grassland birds, but site‐specific predator communities and species‐specific response of target bird species to fences should be assessed before installing fences at other sites. Resumen fr Cercas de exclusión alrededor de nidos de Ammodramus savannarum floridianus en riesgo disminuyen las tasas de depredación por mamíferos Incrementar la supervivencia de los nidos mediante la exclusión de depredadores es uno de los objetivos de muchos programas de conservación de aves. Sin embargo, nuevos proyectos de exclusión deben ser evaluados cuidadosamente para determinar el riesgo potencial del disturbio. Evaluamos la efectividad de cercas excluyentes de depredadores (cercas de aquí en adelante) para nidos del críticamente amenazado Ammodramus savannarum floridianus en un sitio de pradera seca (Three Lakes; 2019‐2018) y un sitio de potrero (the Ranch; 2015‐2016) en el condado de Osceola, Florida, USA. Instalamos cercas en los nidos en promedio ocho días después del inicio de la incubación y el abandono del nido después de la instalación del acerca fue raro (2 de 149 instalaciones). Depredación fue la causa principal de fracaso de los nidos sin cercas en los dos sitios (60.4% vs. 27.7%). Sin embargo, no encontramos diferencias en la supervivencia diaria de los nidos en “the Ranch” entre los años anteriores a la instalación de las cercas (2016; 0.874) y el año en el que todos los nidos excepto uno fueron cercados (2016; 0.867), debido a que las hormigas de fuego (Solenopsis invicta) no nativas fueron responsables por el 86% de los eventos de depredación en “the Ranch”. El uso de cámaras en nidos cercados revelaron que las diferencias especificas al sitio en los depredadores de nidos explican la variación en la eficiencia de las cercas entre los sitios. Nuestro diseño de las cercas puede ser útil para otras especies de aves de pastizales, pero comunidades de depredadores especificas a los sitios y respuestas especificas a las especies que son objetivo para la instalación de cercas deben ser determinadas previo a la instalación de las cercas en otros sitios.
... Az egyéb (6,1%) és az ismeretlen tényezők (9,1%) hatása nem volt meghatározó sem hazánkban, sem pedig Nagy-Britanniában (egyéb: 3,2%); ismeretlen: 6,3%) (HOODLESS & COULSON, 1998). A külföldi szakirodalmi adatok alapján (HIRONS, 1982;NYENHUIS, 1991NYENHUIS, , 2007HOODLESS & COULSON, 1998;ISAKSSON et al., 2007;PEDERSEN et al., 2009) a róka, a vaddisznó, a hermelin, az európai sün, a közönséges erdeiegér, a szajkó és kormos varjú fészekpusztítása számos esetben bizonyított. A fészekpredátorok sorában a magyar szakirodalomban nem közöltek adatot sem a vaddisznóra, sem pedig a vörös rókára vonatkozóan, mindösszesen egy feltételezés ismert a vörös róka predációját illetően (VARGA, 1968). ...
... A fészekpredátorok sorában a magyar szakirodalomban nem közöltek adatot sem a vaddisznóra, sem pedig a vörös rókára vonatkozóan, mindösszesen egy feltételezés ismert a vörös róka predációját illetően (VARGA, 1968). A nemzetközi irodalmi adatok (NYENHUIS, 1991(NYENHUIS, , 2007ISAKSSON et al., 2007;PEDERSEN et al., 2009) és e két faj hazai állományviszonyai alapján valószínűsítjük, hogy fészekpredációs szerepük hazánkban is jelentősebb, míg a vizsgálatunk eredményei szerint meghatározó hányadot képviselő emberi pusztítás valós mértéke valószínűsíthetően jóval kisebb veszteségeket jelent. Ilyen kis elemszámú vizsgálat esetén a fészekalj-pusztulásokból nem lehet egyértelmű következtetést levonni, mindazonáltal az összegzett hazai adatok hiánypótlók, hiszen a nemzetközi szakirodalomból csak Nagy-Britanniából ismertek a veszteségek okait összegző adatok. ...
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The breeding biology of the Woodcock (Scolopax rusticola) on the base of data origin from the territory of the Kingdom of Hungary and in the current territory of Hungary. According to international literature (HIRONS, 1982; HOODLESS, 1994; MORGAN & SHORTEN, 1974; GEMENTIEV & GLADKOV, 1951), the main breeding season of woodcock is in April- May but breeding in March is not uncommon in Great Britain (HIRONS, 1982; HOODLESS, 1994). According to our research, the main breeding period in Hungary is also in April-May; we know more than two-thirds of the nestings from this period. Based on the international literature data and our own results, it is not possible to determine a clear trend-like time shift in the nesting period although the climatic conditions of this widespread breeding distribution, and presumably the altitude as well, affect the timing of the beginning of nesting, e.g., Hoodless (1994). In connection with second breeding, neither the international (LÖNNBERG, 1921; WITHERBY et al., 1941; NIETHAMMER, 1942; MAKATSCH, 1974) nor the Hungarian (ANONYMOUS, 1902; ERTL, 1902; UNGER-ULLMANN, 1934; FARKAS, 1935; PANKA, 1938; ZSILINSZKY, 1943; ANONYMOUS, 1950; AGARDI, 1968; VARGA, 1970; VARGA, 1975; HORVÁTH, 1989; HARASZTHY, 2019; FENYŐSI & STIX, 1993) literature is uniform. Knowing the nesting data from Hungary, in the case of successful early first breeding, we consider the second breeding of the species possible in Hungary as well, considering the nesting data from July and early August. This may not be significant, as the second summer nesting peak does not stand out clearly. Based on the data on nest mortality from Hungary, compared to the British data (32.6%) from Hoodless and Coulson (1998), the rate of loss caused by human factors is very high, which can be attributed to the data of egg collections, which is now outdated. On the other hand, the share of predation (15.2%) is lower than the value (57.9%) from Great Britain. Few pieces of data on natural nest predators are reported in the Hungarian literature, but based on international data, it can be assumed that the loss attributable to this is greater than the domestic data, so the actual rate of human destruction determined by the results of this study might be lower. Comparing the data of scattered nesting in Hungary with the data of the countries with a significant nesting population published in the international literature, it can be stated that there is no significant difference in terms of clutch sizes (3.9 eggs/nest) and the number of chicks raised per hen (2.8 specimens/hen), which refers to the uniform breeding biology of woodcocks throughout Europe.
... One common form of predation management for shorebird nests is predator exclosures (i.e., nest cages; Rimmer and Deblinger, 1990;Melvin et al., 1992), which are nesting-birdpermeable but exclude most avian and mammalian predators from nests . Nest exclosures have repeatedly been documented to improve nest success for piping plovers and other ground-nesting species (Rimmer and Deblinger, 1990;Mabee and Estelle, 2000;Murphy et al., 2003a;Isaksson et al., 2007;Maslo and Lockwood, 2009;Dinsmore et al., 2014;Anteau et al., 2022), but concerns remain regarding how effective they may be at increasing population growth rates or if there are any negative impacts, such as a reduction in incubating adult survival (Murphy et al., 2003b;Roche et al., 2010a;Smith et al., 2011;Gaines et al., 2020;Stantial, 2020). A previous PVA on NGP plovers reported that the use of predator exclosures, which would increase nest and fledgling rates (with no effect on adult survival), would lead to a stable population (Larson et al., 2002). ...
... Other management actions may have a similar effect, but the magnitude of the effect on fecundity would require additional study. The use of nest exclosures on other species where it has been shown to improve fecundity (Rimmer and Deblinger, 1990;Mabee and Estelle, 2000;Isaksson et al., 2007;Dinsmore et al., 2014) may yield similar improved population viability if their use does not affect adult survival as well. Previous simulations indicated that the use of predator exclosures to increase fledging rates could stabilize the NGP population (Larson et al., 2002). ...
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One challenge in wildlife conservation is understanding how various threats and management actions may influence long-term population viability. This is particularly evident when there is considerable uncertainty regarding population structure and vital rates. Reassessment of current knowledge and population trends is necessary for listed species to improve management actions that benefit conservation. We present an updated population viability analysis for northern Great Plains piping plovers ( Charadrius melodus circumcinctus ) based on the latest scientific data on survival, fecundity, and connectivity. Further, we explore the consequences of potential management actions and the stochastic effects of global climate change on population viability through changes in survival and fecundity. Our results predict elevated risks of extinction after 50 years (0.088 – 0.373) compared to previous predictions (0.033) based on assumed conditions of low connectivity among four major breeding groups structured as a metapopulation. We explored eight scenarios based on empirically-derived, higher connectivity rates and found that the northern Great Plains population never had a mean predicted population growth rate greater than one (0.946 – 0.996). Two scenarios that simulated a reduction in adult survival showed higher extinction probabilities (0.267 – 0.373), whereas two other scenarios that simulated an increase in fecundity exhibited lower extinction probabilities (0.088 – 0.103). These results indicate that viability of the northern Great Plains population of piping plovers could be improved with management actions that increase fecundity as long as adult survival is not simultaneously reduced. Lastly, breeding groups appeared to function less independently when connectivity rates were higher, as the breeding population was divided evenly among breeding groups. This indicates that the presumed metapopulation structure of our study system may need to be re-evaluated, and that empirically-based estimates of connectivity are essential to assessing population viability of mobile species that exhibit a spatially structured distribution.
... We suspect that cage design might have contributed to them not causing negative side effects on chick and adult survival. Species-specific behaviors such as flushing distance when a predator approaches can be related to the potential that nest cages contribute to adult mortality and may interact with things like exclosure size (Isaksson et al. 2007). For example, cages have been used extensively for snowy plovers and increase nest survival and fledging rates (Hardy and Colwell 2008). ...
... Nest cages are used for a variety of birds and in a variety of land cover types and the construction of the nest cages varies from site to site and species to species (Johnson and Oring 2002, Murphy et al. 2003b, Gulickx and Kemp 2007, Isaksson et al. 2007). Accordingly, some caution needs to be applied in the scale of inference for the results of our study. ...
Article
Species of conservation concern often receive intensive management to improve vital rates and facilitate recovery. Piping plovers (Charadrius melodus) are federally listed in the United States and concerns over nest depredation have prompted widespread use of plover‐permeable predator exclosures placed around nests (0.5–2‐m radius). While effectiveness of exclosures for improving nest survival has been demonstrated, concerns remain about decreased chick survival (through predator cueing or density‐dependent processes) or increased vulnerability of adults to predation (ambush as adult leaves exclosure). Either one of these concerns could demographically outweigh the benefits of increased nest survival. During 2014–2016, we conducted an experiment designed to evaluate survival of uniquely identified nests (n = 418), chicks (n = 453), and adults (n = 367) at wetlands across the Northern Great Plains, USA. We assigned wetlands (n2014 = 26, n2015 = 28, n2016 = 25) into 2 groups: wetlands in which half of the nests received exclosures and wetlands in which none of the nests received exclosures. Exclosed nests had greater cumulative survival (0.73 [85% CI = 0.70–0.77]) than unexclosed nests at treatment wetlands (0.58 [0.54–0.62]) or unexclosed nests at control wetlands (0.52 [0.49–0.56]). Survival to fledging was highest for chicks hatched from exclosed nests (0.51 [0.47–0.56]), and similar between chicks hatched from unexclosed nests at treatment (0.34 [0.30–0.39]) and control (0.37 [0.32–0.42]) wetlands. Cumulative survival of adults during incubation varied by exclosure status, but adults associated with exclosed nests (0.90 [0.88–0.93]) and unexclosed nests at treatment wetlands (0.89 [0.86–0.92]) had greater survival than those associated with unexclosed nests at control wetlands (0.75 [0.64–0.84]). Adult annual survival rates varied by year (0.79–0.95) but not by exclosure status. The positive influence of exclosures on nest survival was not offset by a reduction in chick or adult survival, indicating that exclosures are a viable tool for piping plover conservation. We conducted an experiment to evaluate if predator exclosures, placed around a nest, were effective at increasing nest survival of piping plovers; we also evaluated if there were any detrimental impacts of exclosures on chick and adult survival. Nest exclosures had a positive influence on nest survival that was not offset by a reduction in chick or adult survival, indicating that exclosures are a viable tool for plover conservation.
... Ground-nesting bird species populations have dramatically decreased during recent decades in Europe [1][2][3] with most dramatic declines reported for larger species such as waders and bustards inhabiting agricultural landscape [2,[4][5][6] or forest grouses (Tetraonidae) [7][8][9][10][11][12]. For example, the long-term population decline and range contraction of black grouse (Lyrurus tetrix) has been recorded in the majority of its distribution area, including the British Isles, continental Europe, and Fennoscandia [7,8,[12][13][14][15][16]. The reasons for population declines are multifactorial, however, they are mainly related to land-use intensification and habitat loss [8,14], climatic change [8], human activities [14,17], and increased predation risk [8,16,18,19]. ...
... Ground-nesting bird species populations have dramatically decreased during recent decades in Europe [1][2][3] with most dramatic declines reported for larger species such as waders and bustards inhabiting agricultural landscape [2,[4][5][6] or forest grouses (Tetraonidae) [7][8][9][10][11][12]. For example, the long-term population decline and range contraction of black grouse (Lyrurus tetrix) has been recorded in the majority of its distribution area, including the British Isles, continental Europe, and Fennoscandia [7,8,[12][13][14][15][16]. The reasons for population declines are multifactorial, however, they are mainly related to land-use intensification and habitat loss [8,14], climatic change [8], human activities [14,17], and increased predation risk [8,16,18,19]. ...
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We evaluated the spatiotemporal patterns of predation risk on black grouse nests using artificial nests that were monitored by camera traps in mountain areas with a small extant (Ore Mts.) and already extinct (Jeseníky Mts.) black grouse population. The overall predation rate of artificial nests was 56% and we found significant differences in survival rate courses over time between both study areas (68% Ore Mts. vs. 41%, Jeseníky Mts.). Within the time required for successful egg incubation (25 days), nest survival probability was 0.32 in the Ore Mts. and 0.59 in Jeseníky Mts. The stone marten (Martes foina) was the primary nest predator in both study areas (39% in total), followed by common raven (Corvus corax, 25%) and red fox (Vulpes vulpes, 22%). The proportion of depredated nests did not differ between habitat types (i.e., open forest interior, clearing, forest edge), but we recorded the effect of interaction of study area and habitat. In Ore Mts., the main nest predator was common raven with seven records (37%). The Eurasian jay (Garrulus glandarius) was responsible for most predation attempts in Jeseníky Mts. (five records, i.e., 83%), while in the Ore Mts., most predation attempts were done by red fox (six records, i.e., 38%).
... Nest exclosures Isaksson et al., 2007;Johnson and Oring, 2002;Neuman et al., 2004;Niehaus et al., 2004) and the predator removal (USFWS 1985(USFWS , 2009Cohen et al. 2009) are commonly used to protect plovers. Indeed, the use of exclosures prior to the flood on the Missouri River increased nest success and great horned owl removal increased chick survival in one of two years studied (2008; . ...
... To combat predation, managers have used nest exclosures (Johnson and Oring 2002, Neuman et al. 2004, Niehaus et al. 2004, Isaksson et al. 2007) and predator removal (USFWS 1985, USFWS 2009Cohen et al. 2009) to increase reproductive output. On the Missouri River, predator exclosures were used on 39-56% of the piping plover nests from 2005-2009, and numerous great horned owls (Bubo virginianus) were trapped and removed off of engineered sandbars from 2007-2010 . ...
... Methods of nest protection are a typical example of conservation decisions that entail uncertainty and risk. Successful protection of eggs and nestlings from predators using some form of exclusion barrier has been achieved in shorebirds (Isaksson, Wallander, & Larsson, 2007), giant ibis Thaumatibis gigantea (Keo, Collar, & Sutherland, 2009) and passerines (Major et al., 2015). However, unexpected negative outcomes have also been reported, such as increased predation on nesting adults (Isaksson et al., 2007) and nest abandonment (Cohen et al., 2016). ...
... Successful protection of eggs and nestlings from predators using some form of exclusion barrier has been achieved in shorebirds (Isaksson, Wallander, & Larsson, 2007), giant ibis Thaumatibis gigantea (Keo, Collar, & Sutherland, 2009) and passerines (Major et al., 2015). However, unexpected negative outcomes have also been reported, such as increased predation on nesting adults (Isaksson et al., 2007) and nest abandonment (Cohen et al., 2016). The potential for either positive or negative outcomes from nest protection can therefore make it difficult to choose the best management alternative. ...
Article
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Abstract Making transparent and rational decisions to manage threatened species in situations of high uncertainty is difficult. Managers must balance the optimism of successful intervention with the risk that intervention could make matters worse. We assessed nest protection options for regent honeyeaters (Anthochaera phrygia) in Australia. Formal expert elicitation highlighted two methods of nest protection expected to improve nest success. However, the risks and benefits of different actions were uncertain; for example, protecting nests from predators might also increase the risk of nest desertion by adults. To avoid risks, the recovery team opted to collect more information before implementation. The two methods of nest protection were compared using a field experiment. However, the same risk aversion limited the experiment to a single variable (nest predation) and dictated the use of artificial nests. The results of the experiment suggested neither action was likely to significantly reduce predation risks (
... It follows that there may be opportunities to assist populations through the breeding season with management aimed at reducing one or more of these threats. For example, successful protection of eggs and nestlings from predators using a type of exclusion barrier has been achieved in passerines (Major et al., 2014), Giant Ibis (Thaumatibis gigantea) (Keo et al., 2009) and shorebirds (Isaksson et al., 2007). However unexpected negative outcomes have also been reported, such as increased predation on nesting adults (Anderson et al., 2003;Isaksson et al., 2007) and potential nest abandonment (Cohen et al., 2016). ...
... For example, successful protection of eggs and nestlings from predators using a type of exclusion barrier has been achieved in passerines (Major et al., 2014), Giant Ibis (Thaumatibis gigantea) (Keo et al., 2009) and shorebirds (Isaksson et al., 2007). However unexpected negative outcomes have also been reported, such as increased predation on nesting adults (Anderson et al., 2003;Isaksson et al., 2007) and potential nest abandonment (Cohen et al., 2016). The potential for either positive or negative outcomes from nest protection can therefore make it difficult to choose the best management alternative and the reason we explore and trial these options before implementing them. ...
Thesis
Reintroductions are becoming an increasingly popular tool for threatened species management and broader scale restoration projects. Reintroductions require a series of important decisions to be made from planning and implementation through to postrelease establishment and persistence of populations. Decision making in reintroduction is frequently impeded by high levels of uncertainty. Linguistic, epistemic and aleatory uncertainties often lead to a failure to meet project objectives. This has led to repeated calls for setting clear objectives and using these to focus monitoring in a way that allows applied science to support management. // Viewed in this way, applied science can naturally assist the decision making process. It is important to reduce only the uncertainties that will help inform the choice between two or more possible actions. These can be reduced through targeted monitoring and research. The failure of applied science to approach research in this way is one possible explanation for the ‘research –implementation gap’ that persists in conservation biology. Throughout this thesis I use decision analytic tools to evaluate and inform the discipline of reintroduction biology. Decision analytic tools are increasingly being utilised in diverse fields of resource management. The benefits for more formally incorporating decision science into conservation biology are obvious and repeatedly lauded, yet it remains unclear how much the approach is used to ensure applied science is truly informing management, particularly in the growing discipline of reintroduction biology. // Overall, my PhD intends to promote the application of formal decision tools to threatened species management and showcase how it can reduce uncertainty and support decision making specifically in reintroductions. In using the Regent Honeyeater recovery actions as a case study, I will evaluate whether management actions to recover the species are working, as well as highlighting areas where resources can be targeted to reduce the uncertainties that influence management decisions, rather than wasting it on those that are not relevant.
... Often a conservation biologist/manager has a variety of choices with control mechanisms, and needs to choose the best possible one, or the best combination of these [73,74]. For example, the population of many bird species have declined globally [75], due to predation by invasive predators [10]. Conservation biologists have used predator exclosure methods with success [75,76], but are often faced with a decision of the most cost effective combination of measures such as exclosure fencing versus nest cover to use [73]. ...
... For example, the population of many bird species have declined globally [75], due to predation by invasive predators [10]. Conservation biologists have used predator exclosure methods with success [75,76], but are often faced with a decision of the most cost effective combination of measures such as exclosure fencing versus nest cover to use [73]. Thus it would make for interesting future work to investigate models, that incorporate a combination of corridors (mixed boundary conditions) coupled with chemical control, and work out optimal scenarios to keep the invasive/pest density low, or drive it towards extinction. ...
Article
population explosions
... For example, O'Connor et al. (2017 found that controlling hunting foxes via lethal removal resulted in a 27% predation rate on sea turtle eggs, while the use of nest covers reduced the predation rate to 3%. However, nest covers that are not properly implemented can be ineffective, or in the worstcase scenario can actually attract predators that learn to associate a nest cover with incubating eggs (Niehaus et al. 2004;Isaksson et al. 2007). The use and design of nest covers therefore requires thoughtful and deliberate planning and should be tailored to the specific predators in a region (Isaksson et al. 2007;O'Connor et al. 2017). ...
... However, nest covers that are not properly implemented can be ineffective, or in the worstcase scenario can actually attract predators that learn to associate a nest cover with incubating eggs (Niehaus et al. 2004;Isaksson et al. 2007). The use and design of nest covers therefore requires thoughtful and deliberate planning and should be tailored to the specific predators in a region (Isaksson et al. 2007;O'Connor et al. 2017). Additionally, nest covers designed in previous studies have been described as having certain disadvantages, including being expensive, heavy, challenging or time consuming to place on nests, and being fully enclosed such that hatchlings cannot crawl freely to sea without human intervention (Lei & Booth 2017;O'Connor et al. 2017). ...
... However, often the specific carnivore species remains unidentified, resulting in surprisingly little information regarding the specific role of particular carnivore species. According to the current state of knowledge, the red fox (Vulpes vulpes) seems to be the most important mammalian predator of ground-nesting birds in Europe (Isaksson et al. 2007;Pedersen et al. 2009;Fletcher et al. 2010;Kämmerle et al. 2017;Roos et al. 2018). However, this seems to be simply a result of the species' high degree of occurrence in a vast distribution range and its ability to occasionally attack and kill even large bird species, such as adult mute swan (Cygnus olor) (Litzbarski 1998;Kube et al. 2005). ...
... However, studies dealing with the predatory potential of different medium-sized carnivore species (mesocarnivores) in Europe reveal that a native species-the red fox (V. vulpes) -is the most important predator of groundnesting birds (Isaksson et al. 2007;Pedersen et al. 2009;Fletcher et al. 2010;Kämmerle et al. 2017;Roos et al. 2018). ...
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In this study, we examine the spatial interrelation between different carnivore species (Carnivora, Mammalia) and ground-nesting birds in a Special Protection Area (SPA) in Brandenburg, Germany. Camera- and live-trapping of carnivores during an 18-month period revealed that the SPA hosts most mesocarnivore species that occur in Germany. Since raccoon (Procyon lotor), red fox (Vulpes vulpes), and domestic cat (Felis silvestris f. catus) showed highest abundance-activity indices, we used GPS telemetry for a detailed analysis of spatial behavior of nine raccoons and five red foxes over a 22-month period. Spatial distribution patterns showed a strong difference between both species: raccoons showed a clear preference for reed swamps and shrub swamps, clustering in high concentrations along the edges of water bodies. Although this behavior is likely due to the high and year-round availability of aquatic food sources, overlap of raccoon core areas with high densities of wetland birds likely results in a high level of sublethal predation effects particularly on waterfowl breeding in reed beds. Red foxes showed much more evenly distributed movement patterns and a high intraspecific variability in habitat preference, revealing a general preference for woodlands and an avoidance of wetlands. Thus, predation pressure by foxes on ground-breeders seems to be lower and focusing on grassland-associated bird species in close proximity to woodlands. Consequently, our study highlights the need for a differentiated view on the predatory potential of particular mesocarnivore species on the endangered bird species in the SPA, leading to future management implications with a focus on swampland habitats.
... Often a conservation biologist/manager has a variety of choices with control mechanisms, and needs to choose the best possible one, or the best combination of these [73,74]. For example, the population of many bird species have declined globally [75], due to predation by invasive predators [10]. Conservation biologists have used predator exclosure methods with success [75,76], but are often faced with a decision of the most cost effective combination of measures such as exclosure fencing versus nest cover to use [73]. ...
... For example, the population of many bird species have declined globally [75], due to predation by invasive predators [10]. Conservation biologists have used predator exclosure methods with success [75,76], but are often faced with a decision of the most cost effective combination of measures such as exclosure fencing versus nest cover to use [73]. Thus it would make for interesting future work to investigate models, that incorporate a combination of corridors (mixed boundary conditions) coupled with chemical control, and work out optimal scenarios to keep the invasive/pest density low, or drive it towards extinction. ...
Article
The control of nonnative species is a central problem in spatial ecology. Data on the invasive Burmese python (Python bivittatus) in the Florida everglades, show an exponential increase in python population, which have resulted in local prey populations reducing severely (Dorcas et al. in Proc Natl Acad Sci 109:2418–2422, 2012). This is exacerbated by the inability to harvest pythons by law, in Everglades National Park, where their concentration is extremely high. We consider a two species predator–prey model with Beddington–DeAngelis functional response, and show that it blows up in finite time, thus mimicking an “exploding” python population. Given current government policy that requires complete protection of species in national parks, we investigate novel alternative population control measures that promote efficient eco-system engineering. We establish such measures are feasible in our setting by rigorously proving boundary damping effects. That is we show that an exploding population in a region can be controlled, solely via manipulation of the boundary, such as effective corridor design. Detailed numerical simulations are performed to justify our analytical results.
... Ces résultats mettent évidence l'efficacité de ces protections contre les prédateurs terrestres mais montrent également que la prédation aviaire n'est pas peut-être si importante sur notre site d'étude. Ce genre de méthode a déjà fait ses preuves dans d'autres pays en améliorant le succès à l'éclosion de plusieurs espèces de limicoles tels que le Vanneau huppé, Vanellus vanellus (Isaksson et al., 2007, Malpas et al., 2013 ou le bécasseau variable Calidris alpina (Pauliny et al., 2008). Bien que cette méthode ne soit pas une solution durable pour assurer le maintien des populations, elle a l'avantage de permettre le marquage des poussins et adultes et ainsi d'estimer leur taux de survie au sein de la population. ...
Technical Report
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Etude comparative de la qualité des habitats au sein des deux secteurs de reproduction du Courlis cendré Numenius arquata dans le département des Deux-Sèvres
... Both species nest on ephemeral environments of European conservation concern (shifting embryonic dunes) and are exposed in the breeding period to several threats, mainly linked to the pressures originated from the use of beaches by people (i.e., mechanical cleaning of the beaches, trampling, and domestic dogs; [10,11]) and by other natural events, especially predation, with crows, gulls, and foxes being the main predators [7,[10][11][12]). The use of anti-predator cages has proved to Conservation 2022, 2 451 be an effective action in order to minimize the risks of predation for these ground-nesting species [6,[13][14][15]. ...
Article
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Beach-nesting birds (plovers; Aves; Charadridae) are impacted by many natural and human-induced threats (e.g., people trampling, dogs, and natural predators). In this regard, the use of anti-predator cages on their nests is effective in order to mitigate some of these pressures (i.e., predation). To evaluate the efficacy of anti-predator cages and the causes of nest failure in a breeding site of two species (Charadrius alexandrinus and C. dubius), we carried out a control-experimental design, comparing false nests (n = 69) in cages (experiment; n = 30) with false nests without cages (control; n = 39). We carried out the study in three seasonal periods (May, June, and July), controlling predations after three periods (three, six, and nine days) since positioning, recording the frequency of eggs still present and evidencing any predation event. The percentage of residual eggs was significantly higher in experimental nests when compared to control nests in all recording periods. Considering 59 predation events on false nests, the most important predators were: in experimental nests (n = 21) the fox, Vulpes vulpes (47.6%), and in control nests (n = 38), the hooded crow, Corvus cornix (50%). Our data suggest that the use of anti-predator cages significantly limits predation on eggs and therefore is likely to increase the hatching success in these ground-nesting birds independently in the seasonal period. However, also in the presence of a cage, the fox is a relevant egg predator.
... However, given continued declines (Smart et al. 2013;Franks et al. 2018;Heldbjerg et al. 2018), it has become clear that wader breeding productivity remains poor without parallel predation management (Smart et al. 2014;McMahon et al. 2020;Laidlaw et al. 2021). Predation risk may be reduced to varying extents, either directly through lethal control of predators (Tapper et al. 1996;Fletcher et al. 2010;Smith et al. 2010;Baines et al. 2023), exclusion fencing (Rickenbach et al. 2011;Smith et al. 2011;Malpas et al. 2013), nest exclosures (Isaksson et al. 2007) or other non-lethal methods (Selonen et al. 2022); or indirectly through habitat management (Laidlaw et al. 2019). Lethal control of both foxes and corvids can substantially benefit ground-nesting bird productivity (Tapper et al. 1996;Fletcher et al. 2010), but may not always be so effective. ...
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The red fox (Vulpes vulpes) is a widely distributed generalist meso-predator implicated in declines of wading bird populations. In the wet grassland habitats where waders breed, wildlife managers work to mitigate fox predation risk to waders during the nesting period through lethal and non-lethal control methods. However, limited knowledge on fox movement ecology in these habitats makes it difficult to design effective management strategies. We used GPS telemetry to understand fox home range size, daily activity and movement patterns, and how these metrics may vary among wet grassland sites with different management. We caught and GPS-tagged 35 foxes in the March–June wader nesting period on two wet grassland sites in central southern England; Britford during 2016/17 and Somerley during 2018/19. We estimated home range areas from location data using local convex hulls, and from these estimates we derived the minimum fox density at each site and year. Daily activity patterns and movement behaviour of each fox were obtained using both telemetry and trail camera data. Mean fox home range area at Britford (0.21 km², SE = 0.025) was significantly smaller than at Somerley (0.68 km², SE = 0.067), and estimated minimum densities were around four times higher (Britford = 10.6 foxes/km², Somerley = 2.4 foxes/km²). Foxes were more active and moved faster during twilight and night hours, but both telemetry and camera data indicate they were also active for one-third of daylight hours. Distances moved per day were variable between foxes but generally smaller at Britford. We also found evidence for dispersal during spring, with movements of up to 19 km per day. Home ranges at both wet grassland sites were smaller than comparable sites elsewhere. These indicated foxes were living at exceptionally high densities at Britford, where there is no fox control, increased food availability and where waders no longer breed. Spatio-temporal movement patterns were closely related to home range metrics, with higher levels of fox activity at Somerley, where home ranges were larger. The movements of itinerant and dispersing foxes during the nesting period suggests that lethal control would need to be very intensive to be effective. The likely anthropogenic food subsidy of fox density at Britford suggests that controlling access to similar food resources would help reduce predation pressure on breeding waders.
... The threat of predation during nest building or the incubation period is a major cause of nest abandonment (Vaske et al. 1994, Nelson & Hamer 1995, Maddox & Weatherhead 2006, Isaksson et al. 2007. Reduced nest concealment has been shown to increase nest predation risks in many passerine species, particularly in cavity-nesting birds (Martin & Li 1992). ...
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The threat of predation is the main cause of bird nest abandonment, with such behaviour imposing considerable energetic costs on breeding birds. However, for several species , nest abandonment can be a less costly alternative to complete brood failure. In this study, we examined nest abandonment among Eurasian Tree Sparrows (Passer montanus) by surveying 71 Tree Sparrow nests with various types of entry holes and conducted artificially manipulating some of the entrance shapes. We found that nest abandonment was caused by changes to the nest entry shape in seven cases and by human interference in two cases. Nest abandonments occurred throughout the breeding season, and breeding pairs attempted to breed again immediately after nest abandonment. The results of the artificial nest entry shape manipulation experiment showed that nine of twelve nests (75.0%) were abandoned where the nest entrance holes were widened, and six of eleven nests (54.5%) were abandoned where the nest entrance holes were narrowed. However, none of the nests were abandoned where the entry shape was unchanged. Thus, nest abandonment by Tree Sparrows is correlated with nest entry shape manipulation and is more likely to occur when the energy cost of breeding again is less than that of abandoning the nest.
... Exclosures have been linked to lower adult survival rates (Gaines et al. 2020) and do not protect chicks from predation once the chicks leave the exclosure. The negative effects of exclosures also have been documented for other shorebird species (Isaksson et al. 2007, Barber et al. 2010. While using exclosures may provide benefits under certain circumstances (e.g., at times or in places with low raptor abundance), for a large part of the range of the plover population, the demographic costs associated with exclosures may outweigh the benefits (Eberhart-Phillips and Colwell 2014, Gaines et al. 2020). ...
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The U.S. Pacific coast population of the western snowy plover (Charadrius nivosus nivosus; plover) has declined due to loss and degradation of coastal habitats, predation, and anthropogenic disturbance. The U.S. Fish and Wildlife Service listed the subspecies in 1993 as threatened under the Endangered Species Act due to the population declines and habitat loss. Predation of nests and chicks has been identified as an important cause of historic population declines, and thus, most predator management actions for this subspecies are focused on reducing this pressure. In recent years, common ravens (Corvus corax; ravens) have become the most common and pervasive predators of plover nests and chicks, especially in areas with subsidized food sources for ravens and sites without predator management. We compiled data from a variety of sources to document the impact of raven predation on plover nesting success. We discuss current raven management and suggest several tools and strategies to increase plover nesting success, including multi-state approval for the use of the avicide DRC-1339, the use of lures and new trap types, and an increase in funding for predator management. The lack of coordinated and integrated management continues to impede the recovery of the Pacific coast plover population. The western snowy plover (Charadrius ni-vosus nivosus; plover) is a small shorebird that nests on sandy beaches and salt pannes (e.g., salt flats or managed ponds) and relies on nest camouflage, precocial chick rearing, and inconspicuous plumage to avoid detection by predators. The Pacific coast population of the plover occurs in coastal habitats ranging from central
... Nest exclosures are a commonly used predator management tactic for snowy plovers and many other shorebird species, primarily to increase nest success (Isaksson et al. 2007, Hardy and Colwell 2008, Dinsmore et al. 2014. Nest exclosures are largely successful in increasing daily nest survival for plovers and have been used extensively across their Pacific coast range (Dinsmore et al. 2014, Lau 2021, Neuman et al. 2021, despite several studies with conflicting results (Murphy et al. 2003, Hardy and Colwell 2008, Burns et al. 2013, Gaines et al. 2020. ...
Article
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Common ravens (ravens; Corvus corax), an adaptable, synanthropic generalist, have thrived coincident with increasing human landscape modifications and fragmentation, consequently affecting their prey, which are often sensitive native and protected species. Ravens are a conservation concern for the protected western snowy plover (plover; Charadrius nivosus nivosus), causing low nest and chick survival in some breeding areas along the Pacific coast of North America. We used a long-term dataset from a breeding snowy plover monitoring program in Point Reyes National Seashore (PRNS) to investigate potential impacts of ravens on snowy plover nest and fledging success. Between 2002 and 2020, ravens accounted for 33.7% of all plover nest failures and 40.8% of unexclosed plover nest failures. Raven activity varied by plover breeding site, with more ravens observed per survey hour at Kehoe Beach and the Abbotts Lagoon restoration area, sites that had lower fledge success than other breeding areas. Binomial generalized linear mixed models found that plover nest success was best explained by raven activity (negative relationship) and use of nest exclosures (positive relationship). Our model results on snowy plover fledge success were less apparent, resulting in difficult management planning for this vital rate when using exclosures. Furthermore, nest exclosures were effective in increasing long-term snowy plover nest success in an ecosystem inundated by high raven activity. Evidence from PRNS and other plover breeding sites along the Pacific coast point to long-term negative impacts from ravens.
... threat statuses, and broad life-history traits (grounddwelling/non-ground dwelling) to provide insights into taxa-specific traits that might lead to higher vulnerability of extirpation. For example, groundnesting birds may be more vulnerable to extirpation due to Australia's invasive predators (Isaksson et al 2007). Our research goals were to provide a taxon-specific evaluation of likely extirpation, based on loss of potentially suitable habitat and range contractions for Australia's threatened terrestrial birds. ...
Article
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Habitat loss is driving the extirpation of fauna across Earth. Many species are now absent from vast areas where they once occurred in inhabited continents, yet we do not have a good understanding of the extent to which different species have been extirpated, nor the degree to which range contractions and habitat loss has contributed to this local extirpation. Here, for the first time, we use a combination of scientific literature, historical sources, spatial data, and expert elicitation to map the past extent of potential habitats, and changes thereto, of 72 of Australia’s most imperilled terrestrial birds. By comparing the area of potential habitat within the past and current ranges of these taxa, we quantify the extent over which each of Australia’s threatened terrestrial birds have likely been extirpated and assess the amount and configuration of potential habitat that remains. Our results show that since 1750 (before European colonization), at least one extant taxon of threatened bird has disappeared from over 530 million hectares (69%) of Australia, through both range contractions and loss of potentially suitable habitat (noting these are not mutually exclusive phenomena). Ten taxa (14%) have likely been extirpated from >99% of their past potential habitat. For 56 taxa (78%), remaining habitat within their current potential habitats has become fragmented. This research paints a sobering picture of the extent of local extirpation of threatened birds from much of Australia over a 250-year time period. By mapping and quantifying this loss, these findings will help refine scientific understanding about the impact of habitat removal and other pervasive threats that are driving this observed extirpation.
... This knowledge can be used to refine the Nunavut and Canadian government management plans for the Mitivik Island eider population. For example, predator control (e.g., chasing polar bears as done in ; or use of nest exclosures such as electric fences, Lokemoen et al. 1982, Isaksson et al. 2007, Davies and Rockwell 2016, Storer et al. 2017) could mitigate the negative consequences (e.g., on recruitment) and conserve important eider populations. Moreover, as government and local communities plan to establish a Marine Protected Area in Northern Hudson Bay, increased population survey efforts in combination with knowledge from Northern communities could help identify potential nesting habitat that may be suitable for eiders to avoid overlap with their recent egg predator. ...
Thesis
Predator-prey dynamics in the Arctic are being altered with changing sea-ice phenology. The increasing frequency of predation on colonial nesting seabird eggs by a rare predator - the polar bear (Ursus maritimus), is a consequence of bears shifting to terrestrial food resources through a shortened seal-hunting season. I study a colony of nesting common eiders (Somateria mollissima) on Mitivik (East Bay) Island, Nunavut, Canada, that is exposed to established nest predators such as arctic fox (Vulpes lagopus), but has recently experienced an increase in polar bear nest predation due to the bears’ lost on-ice hunting opportunities. Given eiders’ limited eco-evolutionary experience with polar bears, my thesis aimed to determine the capacity of incubating eider hens to perceive and respond to this increasing frequency in predation risk from bears. I used eider heart rate and flight initiation distance (FID) as physiological and behavioural metrics, respectively, to characterize the perceived risk of imminent threat posed by simulated predators that differ in evolved familiarity. I then quantified eider heart rate to examine the capacity of incubating hens to dynamically update their perception of risk across variation in real predation risk by polar bears. My results indicate that eiders were less responsive in terms of heart rate to impending visual cues of polar bears in comparison to that of an evolved egg predator (arctic fox), but responded to all simulated threats with similar FIDs. Eiders exhibited mild tachycardia to bears present closer to their nests, but were insensitive to variation in exposure duration to bears. Taken together, these results suggest eiders do not perceive the full risk that bears pose as egg- and adult predators. This thesis provides insight into the mechanisms governing the ability of eiders to cope with polar bears and subsequent fitness consequences due to indirect effects of anthropogenic climate change.
... It has been proposed that corvids are capable of forming a search image following repeated encounters of the same prey (Croze cited in Montevecchi 1976). Therefore, it may be that a sudden increase in nests triggers the formation of such an image, facilitating subsequent predation of this prey (Isaksson et al. 2007). Corvids can also associate other cues including auditory cues (such as parental alarming (Bonnington et al. 2013) or chick begging (McDonald et al. 2009)) with songbird nests and an increase these other cues could further facilitate recognition, and consequent predation, of nests. ...
Article
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Despite the suggestion from several meta-analyses that nest predation is not limiting songbird populations, responses to experimental removal of nest predators, such as corvids, have varied. The impact of nest predation by corvids on songbird populations is unclear. One potential explanation for this disparity is that susceptibility could vary according to the nesting biology of a species. To investigate this hypothesis, we conducted a review of studies detailing nest predation on UK songbirds and extracted the reported rates of nest predation from 80 papers which attempted to identify the predators responsible. We found that corvids were significant predators of songbird nests (24% of nest predation was attributed to corvids). However, species that construct open nests, and whose breeding season overlaps considerably with the breeding season of magpie and jay, incurred the highest rate of nest predation by corvids specifically (different factors predicted predation by non-corvid predators). We then used attributes of nesting biology to predict predation rates for UK breeding species for which we found no empirical data (n = 31). Although, in most cases cited in the literature songbird populations are unaffected by changes in corvid numbers, there are some cases in which species we predicted to be more susceptible to corvid predation responded to changes in corvid numbers. However, an understanding of how of other predators and other non-predation-related factors limit both songbird breeding success and songbird population numbers is necessary in any conservation management of songbird populations.
... Continuing declines of many remaining wader populations are now driven by low breeding success resulting from high egg and chick predation (MacDonald & Bolton, 2008;Roodbergen et al., 2012), especially by mammalian predators (Ausden et al., 2009;Mason et al., 2018;Teunissen et al., 2008). Lethal control of those mammalian predators that are not legally protected can be effective (Bolton et al., 2007;Fletcher et al., 2010), as can the caging of individual wader nests (Isaksson et al., 2007) and fencing of larger areas to exclude mammalian predators (Malpas et al., 2013). Other non-lethal methods of controlling predation, such as conditioned taste aversion, olfactory misdirection, chemical repellents or visual or sonic deterrents have also been used in similar conservation conflict situations with a range of success (Norbury et al., 2021;Smith et al., 2000). ...
Article
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For ground-nesting and colonial bird species, predation of eggs and chicks can exert a strong negative effect on population growth and recovery. For declining populations of waders breeding on lowland wet grassland, predation management tools are available to reduce the impacts of mammalian predators (e.g. lethal control, exclusion), but potential solutions are limited when raptors, which are often themselves protected by law and not easily excluded, are responsible for predation. Diversionary feeding (DF), where predators are provided with alternative food to replace the target prey species in their diet, has been tested successfully by providing food close to nesting raptor pairs to target specific individuals. Where many individuals are involved in predation at a single prey colony, or where locating or accessing nests is difficult, provisioning DF close to the focal prey colony may be a more practical solution. Here, we test the efficacy of providing DF in this way to reduce predation by red kites, a reintroduced and increasingly abundant protected raptor in the UK, on the chicks of northern lapwing, an internationally declining wader species. We conducted a five-year field experiment, comparing kite predation rates and breeding productivity of lapwings in years before, during and after DF. Rates of kite predation on lapwing chicks were substantially and significantly reduced in DF years, due to the successful elimination of a May-June peak in kite predation by DF which coincided with the kite chick provisioning and lapwing chick rearing periods. These annual reductions in kite predatory strike rates were concurrent with marked increases in overall annual lapwing productivity, which more than doubled on average in DF years, and were on a scale sufficient to facilitate lapwing population recovery. DF attracted other potential predators of lapwing eggs and chicks, and more kites were attracted to feeding stations than were initially targeted by DF, but neither had any measurable impact on lapwing breeding success during DF years or after its cessation. With increasing populations of many raptor species, predator-prey conservation conflicts are expected to increase. DF proved to be a highly effective predation management tool for a high-density wader colony on lowland wet grassland where intensive kite predation limited breeding success. Although evaluation of the effects of using DF continuously over several years is needed, targeting multiple predator individuals close to the focal prey of conservation concern may be an important predation management tool where accessing individual raptors at nest sites is impractical.
... 29(1) 132 winged predators of the eggs are the Eurasian Jay (Garrulus glandarius) and the Carrion Crow (Corvus corone corone). Among the mammals, the nest predation of the Wood Mouse (Apodemus sylvaticus), the European Hedgehog (Erinaceus europaeus), the Stoat (Mustela erminea), the Red Fox, and the Wild Boar (Sus scrofa) is known (Nyenhuis 1991, 2007, Isaksson et al. 2007, Pedersen et al. 2009). ...
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Based on 356 observations of Woodcock nestings published in the Hungarian hunting and ornithological literature between 1846 and 2019, which also includes published and unpublished personal observations, it can be stated that the nesting dates of Woodcock in Hungary are scattered over a large interval. 47.3% of all nestings registered with exact dates (n=93) happen in April. The second peak of breeding in June does not stand out significantly. Based on the data of the clutches (n=65) reported with known number of eggs, as well as the clutches (n=14)-probably with full number of eggs-found in the Hungarian egg collections, the average number of eggs per clutch was 3.8. Based on the observational data of the Woodcock families (n=36) observed during the study period, the number of chicks per hen was 3.6, of which the hens were able to raise an average of 2.8 chicks up to a flying age. Összefoglalás A magyar vadászati és ornitológiai szakirodalomban az 1846-2019 között közölt és nem publikált személyes közlések erdei szalonka fészkelésre vonatkozó, 356 megfigyelési adata alapján megállapítható, hogy az erdei szalonkák magyarországi fészkelési időpontjai nagy intervallumon belül szóródnak. Az összes pontos dá-tummal regisztrált fészkelés (n=93) 47,3%-a április hónapra esik. A második, júniusi költési csúcs nem rajzolódik ki markánsan. Az ismert tojásszámmal közölt fészekaljak (n=65) adatai, továbbá a magyarországi tojásgyűjtemé-nyekben lévő-valószínűsíthetően teljes tojásszámú-fészekaljak (n=14) alapján az átlagos fészekaljankénti to-jásszám 3,8 volt. A vizsgált időszakban megfigyelt szalonkacsaládok (n=36) adatai alapján az egy tojóra jutó csi-bék száma 3,6 példány volt, amiből a tojók átlagosan 2,8 csibét tudtak felnevelni röpképes korig.
... Some measures focusing on nest protection could reduce predation by the invasive marmosets, but their implementation may be difficult. For example, both antwren and antshrike build nests in dense vegetation, and installation of protective cages, shown to be effective in groundnesting birds (Isaksson et al. 2007), would certainly cause major disturbance around the nests, and would likely result in their abandonment. It is also not easy to find active nests. ...
Article
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Invasive predators contributed to recent extinctions worldwide, including endemic birds. We monitored nests of two endemic birds in the Atlantic Forest, the serra antwren (Formicivora serrana littoralis) and the sooretama slaty antshrike (Thamnophilus ambiguus) during two consecutive breeding seasons, to estimate predation rates and identify the predators. As invasive marmosets apparently became locally common, we hypothesized that they would prey upon natural nests at a higher rate than native predators. We found 13 nests of the antwren and 15 of the antshrike, of which 100% and 73%, respectively, were preyed upon. Invasive marmosets preyed upon 13 of 16 nests (81%) with identified predators, affecting 90% and 67% of the antwren and the antshrike nests. This study documented that invasive primates negatively affect the breeding success of native birds in Brazil. We highlight the need for urgent measures to manage invasive marmosets to avoid the local extirpation of the endemic birds.
... In RU2, managers used predator exclosures from 2001-06 to improve nest success; this practice anecdotally coincided with a declining trend in annual apparent survival. Predator exclosures, while widely used across the range, became controversial as they were associated with adult mortality (Johnson and Oring 2002, Murphy et al. 2003, Neuman et al. 2004, Isaksson et al. 2007) and population decline (Eberhart-Phillips et al. 2015). In the local population, records indicate one depredated adult recovered at an exclosure, while seven other adults disappeared during incubation at exclosed nest sites . ...
Thesis
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Adult survival is one of the most influential vital rates affecting population growth of iteroparous organisms. Survival often varies annually due to environmental stochasticity. However, drastic variations in annual adult survival rates can have overwhelmingly negative impacts on population viability and growth. In many wild avian populations, adult survival varies between sexes and may owe to unequal risks associated with reproductive roles or predation; this is particularly true among shorebirds. I used mark-resight data from a 19-year study of Western Snowy Plovers (Charadrius nivosus nivosus) in coastal northern California to investigate sex-specific apparent survival of the adult population (N=387). I reported apparent survival (φ) along with standard error (±SE) and 95% confidence intervals, as well as beta estimates (β) with 95% confidence intervals. Apparent survival varied substantially among years (min φ= 0.44±0.07; 0.30-0.57 to max φ = 0.82±0.06; 0.64-0.94), with the minimum occurring in the middle of the study (2006-07) and the maximum occurring in 2009-10. Furthermore, apparent survival varied between sexes, whereby males had higher overall apparent survival (0.72±0.03; 0.30-0.93) than females (0.68±0.03; 0.26-0.91). Average known lifespan of Snowy Plovers within the study was 3.5±2.1 years, with males living longer on average (4.3±2.8 years) than females (3.6±1.9 years). Overall population growth remained stable ( =1.05±0.13 to 1.10±0.12) across the course of the study. Years of substantially low adult survival have directly reduced overall growth potential for the local population. High temporal variance in adult survival produces increased variance in annual population growth rates, with possible implications for extinction risk. Reduced survival in adult female Snowy Plovers has been shown to influence the adult sex ratio of the population, as observed in other Charadrius populations, however that was not evident in this study. Application of demographic parameters in future population viability and growth models will provide a comprehensive understanding of population dynamics and will inform progress toward the recovery of the Pacific Coast population.
... Jednym z takich działań jest ochrona zniesień, polegająca na przykrywaniu gniazd koszami z siatki drucianej. Wydatnie zwiększają one sukces gniazdowy siewek (Dinsmore et al. 2014), ale nierzadko także śmiertelność ptaków dorosłych, gdyż drapieżniki uczą się chwytać je poprzez siatkę i zabijać (Isaksson et al. 2007;Barber et al. 2010;Gaines et al. 2020). Z tego powodu ich stosowanie jest zalecane jedynie, gdy zyski z podwyższonego sukcesu gniazdowego przewyższają ewentualne straty spowodowane zabijaniem ptaków dorosłych (Cohen et al. 2016, Darrah et al. 2020. ...
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1. Czerwone listy to opracowania szacujące ryzyko zagrożenia wymarciem taksonów poddanych analizie. Wyniki czerwonych list są jednym z głównych elementów budowania strategii ochrony gatunków rzadkich i zagrożonych – zarówno globalnie, jak i na poziomie regionalnym. 2. Poprzednia krajowa czerwona lista analizująca status gromady ptaków została opublikowana w roku 2002. Niniejsza publikacja prezentuje aktualny stan zagrożenia krajowej awifauny prawie dwie dekady później, w roku 2020. Opracowanie przygotowano w oparciu o powszechnie uznaną metodykę Międzynarodowej Unii Ochrony Przyrody (IUCN). 3. Do analiz wykorzystano łącznie ok. 1,4 miliona obserwacji ptaków lęgowych z lat 2010–2019, pochodzących z dwóch źródeł: Monitoringu Ptaków Polski (realizowanego na zlecenie Głównego Inspektoratu Ochrony Środowiska) oraz portalu Ornitho.pl. 4. Analizami objęto 230 regularnie lęgowych (po roku 1800) gatunków ptaków Polski, wykluczając gatunki gniazdujące efemerycznie lub nieregularnie. Analizowano trzy parametry kluczowe w ocenie ryzyka ekstynkcji – liczebność, zasięg i trend populacji, uwzględniając również informacje m.in. o strukturze populacji, fragmentacji zasięgu oraz o stanie populacji w krajach ościennych. 5. Przeprowadzone analizy pozwoliły ustalić, że w Polsce w ostatnich 200 latach wymarło 16 gatunków ptaków (kategoria RE), a dalszych 47 gatunków (20% awifauny lęgowej) zagrożonych jest wymarciem, z czego 12 narażonych jest na ekstremalnie wysokie ryzyko wymarcia jako gatunki krytycznie zagrożone (CR). Kolejnych 14 gatunków jest bliskich zagrożenia (NT), dla 8 nie ustalono statusu (DD), a pozostałe 145 (63%) jest aktualnie niezagrożonych (LC). 6. Najbardziej zagrożone grupy ptaków to siewkowe i blaszkodziobe, gdzie odpowiednio aż 70% i 61% gatunków wymaga szczególnej ochrony. Dominujące typy siedlisk, w których występują ptaki zagrożone, to mokradła i łąki w dolinach rzek, zbiorniki wodne i rzeki, a także wybrzeże morskie. Zagrożone ptaki wyraźnie częściej i liczniej występują we wschodniej Polsce. 7. Udział gatunków zagrożonych w kraju jest wyższy niż w Europie i w skali globalnej. Dodatkowo, w porównaniu z poprzednią edycją czerwonej listy, znacznie (o 30%) zwiększyła się liczba gatunków zagrożonych i niemal podwoiła się liczba gatunków wymarłych. 8. Zidentyfikowanie gatunków zagrożonych we wcześniejszych edycjach czerwonych list w zbyt małym stopniu przyczyniło się do poprawy ich statusu. Wśród nielicznych (8) gatunków, które obniżyły w aktualnej czerwonej liście kategorię zagrożenia, jedynie w kilku przypadkach (np. bielik, sokół wędrowny) uznać można, że nastąpiło to na skutek realizacji działań ochronnych. 9. Kluczowym działaniem pozwalającym efektywnie przeciwdziałać powiększaniu się puli gatunków zagrożonych i wymarłych jest ochrona siedlisk. Trzy najistotniejsze zadania w tym zakresie to zaprzestanie działań powodujących niszczenie naturalnych dolin rzecznych i mokradeł, modyfikacja Wspólnej Polityki Rolnej, aby w większym zakresie realizowała cele środowiskowe, a także dostosowanie gospodarki leśnej do wymogów siedliskowych gatunków zagrożonych i rzadkich. 10. Wśród innych, równie istotnych wyzwań w zakresie ochrony gatunków zagrożonych wskazać należy istotne zwiększenie powierzchni i liczby terenów chronionych, w tym obszarów ochrony ścisłej, rozwiązania mające na celu ograniczenie presji wybranych drapieżników, ograniczenie łowiectwa w odniesieniu do ptaków, oraz realizację odpowiednio zaplanowanych prac badawczych i monitoringowych.
... Various lethal and non-lethal means of predator control are used in bird conservation, including predator translocation, exclusion, culling, trapping and poisoning (Conover & Lyons, 2003;Isaksson, Wallander, & Larsson, 2007;Maslo & Lockwood, 2009;Millus, Stapp, & Martin, 2007;Parr, 1993). These methods are often effective in reducing predation, but can also be difficult to implement, are ineffective, expensive, and raise ethical concerns (Bauer, Lisovski, Eikelenboom-Kil, Shariati, & Nolet, 2018;Bolton, Tyler, Smith, & Bamford, 2007;Côté et al., 1997;Kämmerle & Storch, 2019;Madden, Arroyo, & Amar, 2015). ...
Article
The decline of numerous bird species worldwide has been attributed to increased nest predation pressure often associated with anthropogenic factors. Identifying effective management strategies to reduce nest predation is therefore a conservation priority, but tests of management strategies often lack appropriate control treatments. Conditioned Food Aversion (CFA) is a non-lethal method of predator control where distasteful or illness-inducing artificial eggs are used to deliberately deter predators from nests or eggs of vulnerable prey species. Here, we test whether CFA can reduce predation pressure by pied crow on nests using an improved experimental methodology that includes spatial and temporal controls, non-rewarding control egg treatment and concurrent predator monitoring. At the Berg River Estuary, South Africa, we monitored survival of artificial plover-type nests and predator abundance in six sites across three experimental phases (pre-treatment, treatment and post-treatment). During the treatment phase, sites received either illness-inducing (carbachol-treated) or control (water-filled) quail eggs. Our results show that artificial nests survived longer after carbachol treatment in the post-treatment phase, both when compared to the pre-treatment phase and to the control treatment. Nest cameras revealed that pied crow were responsible for nest predation and point counts demonstrated that crow abundance did not change during the study period in control or treatment sites. Together, our results indicate that carbachol treatment induces CFA and reduces artificial nest predation by pied crow, and that mechanistically CFA in crows is likely driven by learning. This study demonstrates the potential for CFA to reduce nest predation and identifies a rigorous methodology for CFA trials.
... The populations of ground-nesting bird species have a declining trend worldwide, partly due to nest predation (Isaksson et al. 2007). This negative trend can be mitigated by predator control or by protecting the nests. ...
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The nests of rare and threatened bird and reptile species that breed on the ground are often attempted to be protected from predators with fences, grids, and various repellent materials. Results of some experiments refer to the repellent function of human scent, whereas others suggest that it has an attractive role. We aimed to investigate how effectively ground nests can be protected from predators if human hair is placed around nests. We performed the experiment in a riverine oak-elm-ash forest using 90 artificial nests, each with 1 quail and 1 plasticine egg: 30 nests were protected with a game fence, 30 nests were surrounded with human hair and 30 nests were unprotected (control). During the 24 days, predators damaged 23% of the nests protected by a game fence, 40% of unprotected nests and 47% of the nests surrounded with hair. The daily survival rate of quail eggs in nests protected with a game fence was significantly higher than the ones in the nests surrounded with human hair. Only 18% of the quail eggs and 36% of plasticine eggs were damaged. Such difference can be explained by the fact that small-bodied birds and mammals could pass through the game fence and left traces on plasticine eggs but they were unable to crack the shell of quail eggs. Within the game fence, denser vegetation can provide better nesting conditions and result in greater breeding success. The repellent role of human hair has not been proved, on the contrary, in some cases we have observed signs of its attractant role, such as small-bodied birds took hair away for nest building.
... We observed daily recess duration influenced daily survival of both nests and females. Shorter daily recess bouts correspond to increased nest attentiveness which may make incubating females more susceptible to predation, particularly by predators that rely on olfactory cues to locate prey (Hubbard et al., 1999;Isaksson et al., 2007;Martin et al., 2015). Alternatively, longer daily recess (Haftorn, 1988;Lyon & Montgomerie, 1985;MacDonald et al., 2013). ...
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Abstract Females must balance physiological and behavioral demands of producing offspring with associated expenditures, such as resource acquisition and predator avoidance. Nest success is an important parameter underlying avian population dynamics. Galliforms are particularly susceptible to low nest success due to exposure of ground nests to multiple predator guilds, lengthy incubation periods, and substantive reliance on crypsis for survival. Hence, it is plausible that nesting individuals prioritize productivity and survival differently, resulting in a gradient of reproductive strategies. Fine‐scale movement patterns during incubation are not well documented in ground‐nesting birds, and the influence of reproductive movements on survival is largely unknown. Using GPS data collected from female wild turkeys (n = 278) across the southeastern United States, we evaluated the influence of incubation recess behaviors on trade‐offs between nest and female survival. We quantified daily recess behaviors including recess duration, recess frequency, total distance traveled, and incubation range size for each nest attempt as well as covariates for nest concealment, nest attempt, and nest age. Of 374 nests, 91 (24%) hatched and 39 (14%) females were depredated during incubation. Average nest survival during the incubation period was 0.19, whereas average female survival was 0.78. On average, females took 1.6 daily unique recesses (SD = 1.2), spent 2.1 hr off the nest each day (SD = 1.8), and traveled 357.6 m during recesses (SD = 396.6). Average nest concealment was 92.5 cm (SD = 47). We found that females who took longer recess bouts had higher individual survival, but had increased nest loss. Females who recessed more frequently had lower individual survival. Our findings suggest behavioral decisions made during incubation represent life‐history trade‐offs between predation risk and reproductive success on an unpredictable landscape.
... Our results can serve as a conservation tool to design targeted anti-predator measures such as nest exclosures. These have been successfully used in numerous other shorebird species [59][60][61][62]. Such strategies may have significant short-term and/or long-term implications on the survival of nests [63]. ...
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Ground-nesting birds face many challenges to reproduce successfully, with nest predation being the main cause of reproductive failure. Visual predators such as corvids and egg-eating raptors, are among the most common causes of nest failure; thus, parental strategies that reduce the risk of visual nest predation should be favored by selection. To date, most research has focused on egg crypsis without considering adult crypsis, although in natural circumstances the eggs are covered by an incubating parent most of the time. Here we use a ground-nesting shorebird, the Kentish plover (Charadrius alexandrinus) as model species to experimentally test whether decoy parents influence nest predation. Using artificial nests with a male decoy, a female decoy or no decoy, we found that the presence of a decoy increased nest predation (N = 107 nests, p < 0.001). However, no difference was found in predation rates between nests with a male versus female decoy (p > 0.05). Additionally, we found that nests in densely vegetated habitats experienced higher survival compared to nests placed in sparsely vegetated habitats. Nest camera images, predator tracks and marks left on eggs identified the brown-necked raven (Corvus ruficollis) as the main visual nest predator. Our study suggests that the presence of incubating parents may enhance nest detectability to visual predators. However, parents may reduce the predation risk by placing a nest in sites where they are covered by vegetation. Our findings highlight the importance of nest site selection not only regarding egg crypsis but also considering incubating adult camouflage.
... unplanned) side effects on non-target conspecific individuals or demographic rates (e.g. Carrete, Donázar, & Margalida, 2006;Isaksson, Wallander, & Larsson, 2007), including carry-over effects that last into subsequent seasons (e.g. Harrison, Blount, Inger, Norris, & Bearhop, 2011;O'Connor & Cooke, 2015;Robb, McDonald, Chamberlain, Reynolds, et al., 2008;Ruffino, Salo, Koivisto, Banks, & Korpimäki, 2014). ...
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Effective evidence‐based conservation requires full quantification of the impacts of targeted management interventions on focal populations. Such impacts may extend beyond target individuals to also affect demographic rates of non‐target conspecifics (e.g. different age classes). However, such collateral (i.e. unplanned) impacts are rarely evaluated despite their potential to substantially alter conservation outcomes. Subsequent management decisions may then be poorly informed or erroneous. We used 15 years of individual‐based demographic data in a ‘before‐after control‐impact’ (BACI) analysis to quantify collateral demographic impacts of a targeted multi‐year supplementary feeding programme designed to increase sub‐adult survival and hence viability of a small, threatened red‐billed chough Pyrrhocorax pyrrhocorax population. Specifically, we assessed whether the intervention also affected adult survival and reproductive success, and whether such collateral effects were themselves sufficient to stabilize population size and hence achieve short‐term conservation aims. The probabilities of adult survival and successful reproduction increased substantially between the ‘before‐feeding’ and ‘during‐feeding’ periods in those choughs associated with supplementary feeding, but not otherwise. Overall breeding success (i.e. number of chicks fledged per occupied territory) also tended to increase, even though brood sizes did not increase. These relationships, which were detectible only through BACI analyses, suggest that supplementary feeding targeted at sub‐adults had unplanned positive impacts on adult demographic rates. Deterministic matrix models designed to project population growth demonstrate that these estimated collateral effects were sufficient to make a substantial contribution to increasing population growth rate and achieving short‐term population stability. Synthesis and applications. Our results indicate substantial positive collateral impacts of a targeted supplementary feeding intervention on population viability, despite no a priori expectation that the non‐target adults were food‐limited. This casestudy illustrates how thorough assessment of collateral impacts of targeted interventions can affect assessment of short‐term efficacy and reveal new opportunities for future interventions, thereby informing subsequent management decisions.
... However, nest predation seems to be in general the most common case of shorebird nest failure (MacDonald & Bolton 2008) and an increase in nest predation rates has been recorded throughout Europe (Roodbergen et al. 2012). Therefore, the use of predator exclusion by nest exclosures (Isaksson et al. 2007), habitat management (Laidlaw et al. 2017) or predator control (Bolton et al. 2007) might be also essential for the multifaceted support of Lapwing breeding success at sites with high predation pressure. ...
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Egg size represents a fundamental predictor of chick mass and body condition. Chicks from bigger eggs have significantly increased survival, especially in precocial species, where chicks must forage for themselves and cope with environmental threats, such as bad weather or predators. Therefore, our understanding of the factors influencing egg size is crucial both from the perspective of their breeding ecology as well as of their conservation. However, studies simultaneously addressing multiple factors and quantifying their influence on egg size in large samples are rare. Here, we test the effect of seasonality, clutch size and nesting habitat on egg size, measured as volume, in a ground-nesting shorebird, the Northern Lapwing Vanellus vanellus, using a sample of 4384 eggs from 1125 clutches in South Bohemia, Czech Republic, during the period between 1988 and 2018. We report a significant decline in egg size over the breeding season, on average bigger eggs in larger clutches with a significant difference between 2-egg and 4-egg clutches, and no direct effect of nesting habitat. From our review of the same predictors across 15 Northern Lapwing populations throughout Europe it is apparent that replacement or late clutches have on average 3–7% smaller eggs than first or early clutches. Nesting habitat only rarely affects egg size and there are no significant differences in egg size between 3-egg and 4-egg clutches. Earlier studies showed that chicks hatching from bigger eggs early in the breeding season performed better, and that there was higher food abundance available for chicks at that time. This fact, together with the documented seasonal decline in egg size, sends an important message to conservationists and policymakers that early breeding attempts may play a pivotal role in safeguarding shorebird breeding productivity.
... Abgesehen von der Prädation durch Greifvögel und Krähen hebt ein Großteil der Studien die Bedeutung von Raubsäugern (Carnivora, Mammalia) am Prädationsgeschehen hervor (Crooks und Soulé 1999;Sanders und Maloney 2002;Engl et al. 2004;Südbeck und Krüger 2004;Gottschalk und Beeke 2014 (Bellebaum 2002;Boschert 2005;Junker et al. 2005;Isaksson et al. 2007;Draycott et al. 2008;Pedersen et al. 2009;Fletcher et al. 2010;Gottschalk und Beeke 2014Carpio et al. 2016;Kämmerle et al. 2017;Roos et al. 2018). Meist wird dabei auf Korrelationen zwischen abnehmenden Vogelbeständen und zunehmend hohen Populationsdichten des Rotfuchses verwiesen. ...
Thesis
Seit mehreren Jahrzehnten nehmen die Bestandszahlen von Bodenbrütern europaweit ab, ein Prozess, der hauptsächlich auf die Intensivierung der Landwirtschaft zurückzuführen ist. In diesem Zusammenhang könnte aber auch die zunehmende Prädation von Raubsäugern (Carnivora, Mammalia) eine wichtige Rolle spielen. Ziel dieser Studie war die Bewertung und Einschätzung des Prädationspotentials ausgewählter Raubsäugerarten auf Bodenbrüter im brandenburgischen Vogelschutzgebiet "Mittlere Havelniederung". Von Mai 2015 bis Juni 2017 wurde die Raumnutzung verschiedener Raubsäugerarten mittels Kamerafallen und einer Telemetriestudie untersucht und anschließend mit den Ergebnissen einer Vogelkartierung verglichen. Ergänzt wurden die Untersuchungen mit einer Losungsanalyse der am häufigsten beobachteten Raubsäugerarten Waschbär (Procyon lotor) und Rotfuchs (Vulpes vulpes). Waschbären wiesen eine hohe Standorttreue sowie eine hohe Präferenz für Gewässer und Feuchtgebiete auf, während Rotfüchse eine hohe intraspezifische Variabilität in Bezug auf ihre Habitatnutzung sowie ein hohes Abwanderungsverhalten zeigten. Die Ergebnisse lassen außerdem ein hohes Prädationspotential des Waschbären auf Wasservögel vermuten, während der Einfluss auf Wiesenbrüter geringer zu sein scheint. Diese scheinen den höchsten Prädationsdruck durch den Rotfuchs zu erfahren. Die Nahrungsanalysen bestätigen diese Ergebnisse und spiegeln auch räumliche Bewegungsmuster beider Arten wieder. Diese Studie liefert als eine der europaweit ersten Studien empirische Belege für ein starkes indirektes und direktes Prädationspotential des Waschbären insbesondere auf Wasservögel. Zudem hebt diese Studie die Notwendigkeit einer differenzierten Betrachtung potenzieller Auswirkungen von Raubsäugern auf Bodenbrüter hervor und gibt einen Hinweis darauf, dass das Prädationspotential einer Raubsäugerart eng mit der Strukturvielfalt eines Lebensraums und somit mit der Intensität der landwirtschaftlichen Bewirtschaftung zusammenhängt.
... Experimental exclosures (sensu Wagg, 1964) have been widely used as treatments to exclude (or statistically control for) the effects of predators, large herbivores, livestock, small mammals or birds on the species richness and recruitment in plant communities (Fraser and Madson, 2008;Jacobs and Naiman, 2008;Levick and Rogers, 2008;Negussie et al., 2008;Olofsson et al., 2008;Shitzer et al., 2008), on the abundance of other animals (Isaksson et al., 2007;Torre et al., 2007;Aerts et al., 2008;Huntzinger et al., 2008) and on processes such as sediment deposition, litter production, soil carbon sequestration and woody plant invasions (Descheemaeker et al., 2006a;2006b;Pei et al., 2008;Shrestha and Stahl, 2008;Yanoff and Muldavin, 2008). ...
Article
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Rehabilitation of degraded land in arid and semiarid environments often involves excluding livestock from degraded sites, creating what are usually but unfortunately not consistently, called _exclosures_. Their main objective is to allow native vegetation to regenerate as a means of providing fodder and woody biomass, to reduce soil erosion and to increase rain water infiltration. We are concerned that some of the alternative names for this practice that are reported in the international literature, including _closed area_, _area closure_ and _enclosure_, may lead to confusion and misunderstanding, especially when these are used as synonyms. Here we aim to illustrate the difference between exclosures and enclosures using recent ecological and environmental literature and provide guidance for their proper use.
... Leaving unmown patches around or using markers at individual nests may reduce agricultural nest loss, but increase vulnerability to predation (Kragten, Nagel, & De Snoo, 2008;Kentie et al., 2015; but see Zámečník, Kubelka, & Šálek, 2018). While effective at increasing nest survival (Pauliny, Larsson, & Blomqvist, 2008;Smith, Pullin, Stewart, & Sutherland, 2011), nest cages are unlikely to benefit chick survival and may potentially increase predation risk of incubating adults or result in nest abandonment (Isaksson, Wallander, & Larsson, 2007). Fencing is also effective at increasing nest survival (Malpas et al., 2013;Smith et al., 2011), and for large fenced areas may additionally enhance chick survival (Rickenbach et al., 2011). ...
Article
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Farmland birds are among the most threatened bird species in Europe, largely as a result of agricultural intensification which has driven widespread biodiversity losses. Breeding waders associated with grassland and arable habitats are particularly vulnerable and a frequent focus of agri‐environment schemes (AES) designed to halt and reverse population declines. We review existing literature, providing a quantitative assessment of the effectiveness of policy and management interventions used throughout Europe to improve population and demographic metrics of grassland‐breeding waders. Targeted AES and site protection measures were more likely to be effective than less targeted AES and were ten times more likely to be effective than would be expected by chance, particularly for population trend and productivity metrics. Positive effects of AES and site protection did not appear synergistic. Management interventions which had the greatest chance of increasing population growth or productivity included modification of mowing regimes, increasing wet conditions, and the use of nest protection. Success rates varied according to the species and metric being evaluated. None of the policy or management interventions we evaluated were associated with a significant risk of negative impacts on breeding waders. Our findings support the use of agri‐environment schemes, site protection, and management measures for grassland‐breeding wader conservation in Europe. Due to publication bias, our findings are most applicable to intensively managed agricultural landscapes. More studies are needed to identify measures that increase chick survival. Despite broadly effective conservation measures already in use, grassland‐breeding waders in Europe continue to decline. More research is needed to improve the likelihood and magnitude of positive outcomes, coupled with wider implementation of effective measures to substantially increase favorable land management for these species.
... However, due to intensified land management practices and subsequent conversion and loss of habitat, wader bird populations have declined over the past four decades (International Wader Study Group 2003;Ottvall and Smith 2006). Additionally, modification of traditional farming practices, drainage and altered hydrological regimes, climate change, and increased predators pressure have been put forward as factors contributing to the decline in wetland bird populations (Gill et al. 2007;Isaksson et al. 2007;Schekkerman et al. 2008;Teunissen et al. 2008;Roodbergen et al. 2011;Manton 2016). ...
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Abandonment of traditional farming practices, such as hay-making and pasturing, has resulted in rapid loss of open wet grassland habitats in Europe. The globally threatened Aquatic Warbler (Acrocephalus paludicola L.) is a bird species that occurs almost exclusively in open fen mires, which have virtually disappeared in Western Europe, but still persist locally in Eastern Europe. Focusing on the world’s most important breeding site for Aquatic Warbler, the Zvaniec fen mire in Belarus, we estimated Belarusian citizens’ willingness-to-pay for adequate conservation management of this fen mire and its focal species the Aquatic Warbler. Results from a discrete choice experiment indicated that Belarusian citizens were willing to pay for appropriate conservation programmes of the Zvaniec fen mire. Scything and mechanical mowing were preferred compared to controlled burning, and especially over herbicide treatment of encroaching shrubs. Conservation management was preferred over legal protection of wetland areas without management. Respondents considered such passive conservation to be insufficient to maintain open fen mire habitat and gave a higher priority to active conservation management programmes. These preferences are consistent with evidence-based knowledge about what is effective conservation management for the Aquatic Warbler. Given the gradual disappearance of Europe’s traditional cultural landscapes, we discuss the challenge to fund the maintenance of this biocultural biodiversity legacy.
... Sensitivity and elasticity analyses of the population model indicated that activities that increase the likelihood of hatching and fledging success will have a relatively large positive impact on population growth rates. Similar activities have been adopted in the management of other shorebird species (Isaksson et al. 2007), such as the Piping Plover (Charadrius melodus), where it is common to erect physical barriers to nest predators (Mabee and Estelle 2000;Maslo and Lockwood 2009). The other vital rate with a notable effect on population growth rate was adult survival, a common finding for long-lived vertebrates (Saether and Bakke 2000). ...
Article
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Count data suggest that Black Oystercatcher (Haematopus bachmani) has locally variable but globally stable populations. A simple, stage-based matrix population model for Black Oystercatcher was built and Monte Carlo simulations of the model were conducted using vital rates from peer-reviewed and gray literature. Simulations yielded a distribution of potential population growth rates that extended from 0.87 to 1.14 and was centered at 1.00, supporting the hypothesis of a globally stable Black Oystercatcher population. Sensitivity and elasticity analyses of the population model showed that potential population growth is particularly sensitive to changes in hatching success (i.e., proportion of eggs hatched), fledging success (i.e., proportion of chicks fledged), and breeding adult annual survival. These rates could be possible targets for population management should it become necessary given future changes in sea temperature, sea level, and coastal development. Pair productivity, which integrates hatching and fledging success, is suggested as a simple and valuable metric for monitoring population growth potential of Black Oystercatcher.
... However, partial nest predation can create conflicting evidence, leading to inconclusive assignments of nest fate (Lariviere 1999). As a result, the prevalence of partial nest predation is poorly understood in most systems (Lariviere 1999, Ackerman et al. 2003, Isaksson et al. 2007). In our study areas, partial predation was relatively common (19% of all successful nests). ...
Article
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Nest survival is a key demographic parameter, yet little effort has been made to improve accuracy of field‐based methods for assigning nest fates to shorebird nests. We used remote cameras to validate estimates of nest fate from field methods and to assess variation in accuracy of nest‐fate assignment for Snowy Plover Charadrius nivosus in Utah, USA. We correctly identified the fates of 84% of nests in the field and photos from camera monitoring revealed incorrect assignments for 22% of successful nests and 7% of depredated nests. Traditional field methods could be improved by checking nests more frequently when hatching date nears and spending additional time searching for eggshell evidence, especially when nests are in areas susceptible to weather disturbance. This article is protected by copyright. All rights reserved.
... Remarkably, these gains in reproductive output were achieved without predator management, compared with intensive predator management on engineered sandbars prior to the flood . Nest exclosures and predator removal are commonly used to protect beachnesting birds (U.S. Fish and Wildlife Service 1985, 2009, Johnson and Oring 2002, Neuman et al. 2004, Niehaus et al. 2004, Isaksson et al. 2007, Cohen et al. 2009, Catlin et al. 2011b. Indeed, use of exclosures prior to the flood on the Missouri River increased nest success, and Great Horned Owl removal increased chick survival in 1 of 2 yr studied (Catlin et al. 2011a. ...
Article
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Globally, riparian ecosystems are in decline due to anthropogenic modifications, including damming. Reduced frequency and altered timing of flood events decreases sandbar deposition, which reduces habitat for sandbarbreeding birds, including the threatened Piping Plover (Charadrius melodus). In response to limited breeding habitat and small populations, the U.S. Army Corps of Engineers constructed 255 ha of sandbar habitat on the Missouri River, USA, from 2004 to 2009. During the breeding seasons of 2010 and 2011, historically high flows resulted in the creation of 1,046 ha of suitable sandbar habitat on the Missouri River. We compared the demographic responses of Piping Plovers to this anthropogenic and natural habitat creation. We found that demographic parameters, including nest success (xpreflood=0.45 ± 0.02 SE vs. xpostflood=0.74 ± 0.02 SE), prefledging chick survival (xpreflood=0.39 ± 0.09 SE vs. xpostflood = 0.65 ± 0.03 SE), and hatch-year survival (xpreflood = 0.16 ± 0.03 SE vs. xpostflood = 0.46 ± 0.03 SE), were consistently higher on the flood-created habitat than on the engineered habitat, leading to population growth after the flood. These differences were related to increased sandbar habitat, low nesting densities, and decreased nest and chick predation. As ecosystems are increasingly altered, ecologists seldom have the opportunity to make appropriate comparisons between managed and natural ecosystem processes. Our results suggest that management intervention may not be an appropriate substitute for natural ecosystem processes in riparian ecosystems. Q2018 American Ornithological Society.
... Numerous predator guard designs are currently used to limit predator access to nest boxes (McLaughlin and Grice 1952, Bellrose 1955, Cronan 1957, Webster and Uhler 1964, Zeleny 1976. In contrast to the extensive literature on the utility of predator exclusion cages for ground-nesting birds (e.g., Johnson and Oring 2002, Murphy et al. 2003, Isaksson et al. 2007, Maslo and Lockwood 2009, Smith et al. 2011, only a few local studies have tested the effectiveness of antipredator devices for influencing nesting success by cavitynesting birds (Bolen 1967, Yamaguchi et al. 2005, Cornell et al. 2011. We have found no comprehensive study comparing the effectiveness of commonly used nest-box predator guards across a variety of cavity-nesting species in North America. ...
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Humans have long provided nest boxes in a widespread and popular effort to augment nesting sites for cavity-nesting birds. Nest boxes, however, may provide easy access for predators and thereby create ecological traps for nesting birds. Predator exclusion techniques are often deployed at nest boxes to reduce nest predation, but few studies have tested their performance. For the first time, we test the effectiveness of predator guards in promoting the nesting success of multiple species of birds at a large spatial scale (United States and Canada). We used nest fate data from 24,114 nest records submitted from 2014 to 2016 to NestWatch, a citizen-science program focused on quantifying nesting success, to determine whether installing predator guards on nest boxes is an effective management technique. Across all species, top models predicting daily nest survival rates suggest a positive influence of predator guards, with a nearly 7% increase in nest success for attempts in boxes with guards versus attempts in boxes without guards. At the species level, nest survival was greater for individuals nesting in boxes with guards in 7 of 9 species, with no effect in the remaining 2 species. Although all types of guards were correlated with improved nesting success, birds nesting in boxes with cone-type baffles, stovepipe baffles, or entrance hole extenders were most likely to result in successful nesting. Further, birds nesting in boxes with multiple predator guards were more successful, on average, than birds nesting in boxes with only a single guard. Our results can help managers of cavity-nesting birds incorporate science-based evidence into decision-making and allocate resources more effectively.
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Four-toed salamanders Hemidactylium scutatum have disjunct populations in the United States and Canada. Increased predation could threaten their populations and cause them to become limited in certain areas. Installing cages to protect threatened populations can reduce the chance of predation. To test the efficacy of cages, we examined the effects of caging four-toed salamander nests in northeastern Tennessee. We randomly selected 65/120 nests to cage from our study sites at the South Holston Weir Dam and Bouton Tract in Sullivan County, Tennessee. Based on photos from a camera trapping survey, we found that raccoons Procyon lotor were the main predators of uncaged four-toed salamander nests. Raccoon damage resulted in portions of moss being ripped away and the disappearance of eggs. Twenty-six percent of uncaged nests were preyed upon, whereas none of the caged nests were preyed upon. Our findings provide a strategy for improving nest success of four-toed salamanders and could be used to protect threatened populations.
Chapter
The successful conservation of bird species relies upon our understanding of their habitat use and requirements. In the coming decades the importance of such knowledge will only grow as climate change, the development of new energy sources and the needs of a growing human population intensify the, already significant, pressure on the habitats that birds depend on. Drawing on valuable recent advances in our understanding of bird-habitat relationships, this book provides the first major review of avian habitat selection in over twenty years. It offers a synthesis of concepts, patterns and issues that will interest students, researchers and conservation practitioners. Spatial scales ranging from landscape to habitat patch are covered, and examples of responses to habitat change are examined. European landscapes are the main focus, but the book has far wider significance to similar habitats worldwide, with examples and relevant material also drawn from North America and Australia.
Chapter
The successful conservation of bird species relies upon our understanding of their habitat use and requirements. In the coming decades the importance of such knowledge will only grow as climate change, the development of new energy sources and the needs of a growing human population intensify the, already significant, pressure on the habitats that birds depend on. Drawing on valuable recent advances in our understanding of bird-habitat relationships, this book provides the first major review of avian habitat selection in over twenty years. It offers a synthesis of concepts, patterns and issues that will interest students, researchers and conservation practitioners. Spatial scales ranging from landscape to habitat patch are covered, and examples of responses to habitat change are examined. European landscapes are the main focus, but the book has far wider significance to similar habitats worldwide, with examples and relevant material also drawn from North America and Australia.
Chapter
The successful conservation of bird species relies upon our understanding of their habitat use and requirements. In the coming decades the importance of such knowledge will only grow as climate change, the development of new energy sources and the needs of a growing human population intensify the, already significant, pressure on the habitats that birds depend on. Drawing on valuable recent advances in our understanding of bird-habitat relationships, this book provides the first major review of avian habitat selection in over twenty years. It offers a synthesis of concepts, patterns and issues that will interest students, researchers and conservation practitioners. Spatial scales ranging from landscape to habitat patch are covered, and examples of responses to habitat change are examined. European landscapes are the main focus, but the book has far wider significance to similar habitats worldwide, with examples and relevant material also drawn from North America and Australia.
Chapter
The successful conservation of bird species relies upon our understanding of their habitat use and requirements. In the coming decades the importance of such knowledge will only grow as climate change, the development of new energy sources and the needs of a growing human population intensify the, already significant, pressure on the habitats that birds depend on. Drawing on valuable recent advances in our understanding of bird-habitat relationships, this book provides the first major review of avian habitat selection in over twenty years. It offers a synthesis of concepts, patterns and issues that will interest students, researchers and conservation practitioners. Spatial scales ranging from landscape to habitat patch are covered, and examples of responses to habitat change are examined. European landscapes are the main focus, but the book has far wider significance to similar habitats worldwide, with examples and relevant material also drawn from North America and Australia.
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Long-term population trends are considerable sources of information to set wildlife conservation priorities and to evaluate the performance of management actions. In addition, trends observed in functional groups (e.g., trophic guilds) can provide the foundation to test specific hypotheses about the drivers of the observed population dynamics. The aims of this study were to assess population trends of breeding birds in Lombardy (N Italy) from 1992 to 2019 and to explore the relationships between trends and species sharing similar ecological and life history traits. Trends were quantified and tested for significance by weighted linear regression models and using yearly population indices (median and 95% confidence interval) predicted through generalized additive models. Results showed that 45% of the species increased, 24% decreased, and 31% showed non-significant trends. Life history traits analyses revealed a general decrease of migrants, of species with short incubation period and of species with high annual fecundity. Ecological traits analyses showed that plant-eaters and species feeding on invertebrates, farmland birds, and ground-nesters declined, while woodland birds increased. Further studies should focus on investigation of the relationship between long-term trends and species traits at large spatial scales, and on quantifying the effects of specific drivers across multiple functional groups.
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Effective long-term management is needed to address the impacts of invasive alien species (IAS) that cannot be eradicated. We describe the fundamental characteristics of long-term management policies for IAS, diagnose a major shortcoming, and outline how to produce effective IAS management. Key international and transnational management policies conflate addressing IAS impacts with controlling IAS populations. This serious purpose-implementation gap can preclude the development of broader portfolios of interventions to tackle IAS impacts. We posit that IAS management strategies should directly address impacts via impact-based interventions, and we propose six criteria to inform the choice of these interventions. We review examples of interventions focused on tackling IAS impacts, including IAS control, which reveal the range of interventions available and their varying effectiveness in counteracting IAS impacts. As the impacts caused by IAS increase globally, stakeholders need to have access to a broader and more effective set of tools to respond.
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Effective long-term management is needed to address the impacts of invasive alien species (IAS) that cannot be eradicated. We describe the fundamental characteristics of long-term management policies for IAS, diagnose a major shortcoming, and outline how to produce effective IAS management. Key international and transnational management policies conflate addressing IAS impacts with controlling IAS populations. This serious purpose-implementation gap can preclude the development of broader portfolios of interventions to tackle IAS impacts. We posit that IAS management strategies should directly address impacts via impact-based interventions, and we propose six criteria to inform the choice of these interventions. We review examples of interventions focused on tackling IAS impacts, including IAS control, which reveal the range of interventions available and their varying effectiveness in counteracting IAS impacts. As the impacts caused by IAS increase globally, stakeholders need to have access to a broader and more effective set of tools to respond.
Article
If the number of eggs in a clutch is reduced by predators, birds have to decide whether to continue investing time and energy in this clutch or begin a new one. The aim of this study was to assess the desertion frequency of nests with an experimentally reduced number of eggs depending on the stage of incubation, degree of clutch reduction and advancement of the breeding season in the Blackcap Sylvia atricapilla. Only five-egg clutches, most typical for Blackcaps, were investigated. At the beginning of the incubation period (one day after the last egg was laid) or at the end of incubation (10 days after the last egg), two or three eggs were removed. On the next day the clutch was monitored for desertion/incubation. Blackcaps deserted clutches significantly more often when these were reduced by three eggs at the onset of incubation (56 out of 59 clutches) compared to clutches reduced at the end of incubation (33 out of 81 clutches). As the breeding season progressed there was a significant decrease in the proportion of nests that were deserted after a three-egg clutch reduction at the end of incubation. The advancement of the breeding season did not affect the desertion frequency when eggs were removed at the beginning of incubation. Blackcaps continued incubation of all clutches reduced by two eggs (n = 20), despite reduction occurring at the beginning of incubation and early in the breeding season. These results are consistent with predictions from life-history theory in general, and the brood value hypothesis in particular.
Research
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A review of the literature on the impacts of corvid predation on threatened and endangered species in California.
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At 22 wetland localities in SW Sweden, breeding densities of two passerines, Yellow Wagtail and Meadow Pipit, were higher within Lapwing territories than outside them. Earlier studies of predation on artificial nests have shown that the anti-predator aggression of nesting Lapwings results in a reduction of predation on nearby nests. We suggest therefore, that the breeding association of the two passerines and Lapwings is an anti-predator adaptation.
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Mayfield's method for calculating the success of a group of nests is examined in detail. The standard error of his estimator is developed. Mayfield's assumption that destroyed nests are at risk until the midpoint of the interval between visits leads to bias if nests are visited infrequently. A remedy is suggested, the Mayfield-40% method. I also present a competing model, which recognizes that the actual destruction date of a failed nest is unknown. Estimated daily mortality rates and standard errors are developed under this model. A comparison of the original Mayfield method, the Mayfield-40% method, and the new method, which incorporates an unknown date of destruction, shows that the original or modified Mayfield method performs nearly as well as the more appropriate method and requires far easier calculations. A technique for statistically comparing daily mortality rates is offered; the one proposed by Dow (1978) is claimed to be misleading. Finally, I give a method for detecting heterogeneity among nests and an improved estimator, if it is found.
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The control of predators for nature conservation purposes is becoming an increasingly important issue. The growing populations of predator species in some areas and the introduction of predators in other areas have led to concerns about their impact on vulnerable bird species and to the implementation of predator control in some cases. This is set against a background of increasingly fragmented semi-natural habitats and declining populations for many species. To assess the efficiency of predator removal as a conservation measure, the results of 20 published studies of predator removal programs were meta-analyzed. Removing predators had a large, positive effect on hatching success of the target bird species, with removal areas showing higher hatching success, on average, than 75% of the control areas. Similarly, predator removal increased significantly post-breeding population sizes (i.e. autumn densities) of the target bird species. The effect of predator removal on breeding population sizes was not significant, however, with studies differing widely in their reported effects. We conclude that predator removal often fulfills the goal of game management, which is to enhance harvestable post-breeding populations, but that it is much less consistent in achieving the usual aim of conservation managers, which is to maintain and, where appropriate, increase bird breeding population sizes. This may be due to inherent characteristics of avian population regulation, but also to ineffective predator removal and inadequate subsequent monitoring of the prey populations.
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In 2001, predator exclosures were used to protect nests of the Western Sandpiper (Calidris mauri) in western Alaska. During the exclosure experiment, nest contents in exclosures had significantly higher daily survival rates than control nests, however, late in the study predators began to cue in on exclosures and predate the nest contents. An Arctic Fox (Alopex lagopus) dug under one exclosure and took the newly hatched chicks, and Long-tailed Jaegers (Stercorarius longicaudus) learned to associate exclosures with active nests and repeatedly visited them. The jaegers attempted to gain access to exclosed nests and pursued adult sandpipers as they emerged from the exclosures. The exclosures were removed to reduce potential mortality to adult and young sandpipers, but subsequently, post-exclosure nests had lower daily survival rates than controls during the same time period. Predation of post-exclosure eggs and chicks highlighted the lasting influence of the exclosure treatment on offspring survival because predators probably remembered nest locations. Researchers are urged to use caution when considering use of predator exclosures in areas where jaegers occur.
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We identified causes of nest failure and assessed the effectiveness of predator exclosures at Piping Plover (Charadrius melodus), Snowy Plover (C. alexandrinus), and Killdeer (C. vociferus) nests in southeastern Colorado during 1994–1995. Predation, nest abandonment, and weather were the primary causes of nest failure in all three species. For any of the three species we found no significant difference in the daily survival rate between nests that were protected by predator exclosures and nests that were unprotected. We reevaluated the experimental design and data analysis of previous predator exclosure studies and identified several confounding factors, including non-random assignment of exclosures, unbalanced sample sizes between protected and unprotected nests, data pooling across years, and inappropriate statistical analyses. We suggest ways to design (e.g., randomly allocate exclosures to nests and balance sample sizes between protected and unprotected nests) and analyze (e.g., use Mayfield method) future predator exclosure studies.
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To boost productivity in the Piping Plovers (Charadrius melodus) breeding in the northern Great Plains, predator exclosure “cages” constructed of wire mesh fence were placed over 1,355 plover nests on alkali lake beaches in Alberta, Saskatchewan, North Dakota, and Montana during 1993-2002. Nesting plovers were killed, apparently by raptors, near cages at 68 (5%) of the nests. In contrast, no losses of adult plovers were detected at 420 nests that were not covered by cages. The predation was greatest (up to 48% of applications) when small (1-1.7 m) diameter cages with wire mesh tops were used at sites with low (mean, 4%) or moderate (15%) tree cover within two km. In areas with low tree cover, predation decreased to 0.7% of applications/year when large (3-4 m) diameter cages with soft netting tops replaced other designs. No predation was recorded in 393 applications of small cages at plover nests along the relatively treeless North Dakota-Montana border. Predator exclosure cages should be used cautiously for protecting eggs of endangered shorebirds. In some situations, enhanced productivity from use of the cages is outweighed by risks to adult birds.
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A conservation project aimed at ecosystem restoration had several unforeseen effects on a colony of the yellow-legged gull Larus michahellis in a small western Mediterranean island (Benidorm Island). The project included regulation of massive tourist visits to help restore the soil and autochthonous vegetation. However, gulls habituated rapidly to regulation of tourist activities, as nests located either close to or far from the main trail showed a similar hatching success. The quiet conditions produced by regulation seemingly facilitated a rapid colony increase. Partial removal of alien vegetation (Opuntia maxima) showed that gulls had a preference for sites with high vegetation cover because the growth of the colony was proportionally larger in well-vegetated plots. The pricking of a large number of gull eggs surprisingly coincided with a high reproductive success compared to the previous year, although indicators of food availability remained constant between years and the colony had decreased in numbers. Untreated nests were probably more successful because territory size for chicks increased and intraspecific predation decreased. Extreme care must be taken when planning ecosystem-wide management on islands with yellow-legged gull colonies, or other gull species locally considered as pests, to prevent unwanted effects.
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To ensure that the best scientific evidence is available to guide conservation action, effective mechanisms for communicating the results of research are necessary. In medicine, an evidence-based approach assists doctors in applying scientific evidence when treating patients. The approach has required the development of new methods for systematically reviewing research, and has led to the establishment of independent organizations to disseminate the conclusions of reviews. (1) Such methods could help bridge gaps between researchers and practitioners of environmental conservation. In medicine, systematic reviews place strong emphasis on reviewing experimental clinical trials that meet strict standards. Although experimental studies are much less common in conservation, many of the components of systematic reviews that reduce the biases when identifying, selecting and appraising relevant studies could still be applied effectively. Other methods already applied in medicine for the review of non-experimental studies will therefore be required in conservation. (2) Using systematic reviews and an evidence-based approach will only be one tool of many to reduce uncertainty when making conservation-related decisions. Nevertheless an evidence-based approach does complement other approaches (for example adaptive management), and could facilitate the use of the best available research in environmental management. (3) In medicine, the Cochrane Collaboration was established as an independent organization to guide the production and dissemination of systematic reviews. It has provided many benefits that could apply to conservation, including a forum for producing and disseminating reviews with emphasis on the requirements of practitioners, and a forum for feedback between researchers and practitioners and improved access to the primary research. Without the Cochrane Collaboration, many of the improvements in research communication that have occurred in medicine over the last decade would not have been possible.
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In this paper, the main aspects of agricultural intensification that have led to population declines in farmland birds over the past 50 years are reviewed, together with the current state of knowledge, and the effects of recent conservation actions. For each of 30 declining species, attention is focused on: (1) the external causes of population declines, (2) the demographic mechanisms and (3) experimental tests of proposed external causal factors, together with the outcome of (4) specific conservation measures and (5) agri-environment schemes. Although each species has responded individually to particular aspects of agricultural change, certain groups of species share common causal factors. For example, declines in the population levels of seed-eating birds have been driven primarily by herbicide use and the switch from spring-sown to autumn-sown cereals, both of which have massively reduced the food supplies of these birds. Their population declines have been associated with reduced survival rates and, in some species, also with reduced reproductive rates. In waders of damp grassland, population declines have been driven mainly by land drainage and the associated intensification of grassland management. This has led to reduced reproductive success, as a result of lowered food availability, together with increased disturbance and trampling by farm stock, and in some localities increased nest predation. The external causal factors of population decline are known (with varying degrees of certainty) for all 30 species considered, and the demographic causal factors are known (again with varying degrees of certainty) for 24 such species. In at least 19 species, proposed causal factors have been tested and confirmed by experiment or by local conservation action, and 12 species have been shown to benefit (in terms of locally increased breeding density) from options available in one or more agri-environment schemes. Four aspects of agricultural change have been the main drivers of bird population declines, each affecting a wide range of species, namely: (1) weed-control, mainly through herbicide use; (2) the change from spring-sown to autumn-sown cereal varieties, and the associated earlier ploughing of stubbles and earlier crop growth; (3) land drainage and associated intensification of grassland management; and (4) increased stocking densities, mainly of cattle in the lowlands and sheep in the uplands. These changes have reduced the amounts of habitat and/or food available to many species. Other changes, such as the removal of hedgerows and ‘rough patches’, have affected smaller numbers of species, as have changes in the timings of cultivations and harvests. Although at least eight species have shown recent increases in their national population levels, many others seem set to continue declining, or to remain at a much reduced level, unless some relevant aspect of agricultural practice is changed.
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Lowland wet grassland in western Europe is often managed for breeding wading birds, especially lapwing Vanellus vanellus , redshank Tringa totanus , snipe Gallinago gallinago and black‐tailed godwit Limosa limosa . Recommended conservation management often entails introducing winter flooding, and in Britain there is government funding to encourage this through the Environmentally Sensitive Area scheme. Soil macroinvertebrates are important prey for breeding wading birds on lowland wet grassland. This study quantified the response of soil macroinvertebrates to flooding, their ability to survive in flooded grassland, and changes in the abundance and physical availability of soil macroinvertebrates for feeding wading birds as flood water subsides. Unflooded grasslands contained high biomasses of soil macroinvertebrates, comprising mainly Tipulidae larvae and earthworm species that are widespread in pastures. Grasslands with a long history of winter flooding contained much lower biomasses of soil macroinvertebrates, comprising mainly a limited range of semi‐aquatic earthworm species. Introducing winter flooding to previously unflooded grassland greatly reduced soil macroinvertebrate biomass. This was mainly due to the majority of earthworms vacating the soil soon after the onset of flooding. However, when earthworms were artificially confined in flooded soils, most species were capable of surviving periods of at least 120 days continual submergence. Winter flooding also expelled large numbers of overwintering arthropods from the soil. Soil macroinvertebrates were slow to recolonize winter‐flooded grassland when it was re‐immersed in spring. Consequently, prey biomass for breeding wading birds remained low in areas that had been flooded during the preceding winter. However, winter flooding probably benefited breeding snipe by helping keep the soil soft enough for them to probe for prey. It also probably benefited breeding lapwings and redshank by helping keep the sward short and open enough for them to feed in during the latter part of their breeding season. Pools of winter flood water that remained in spring and early summer also provided a source of aquatic invertebrate prey for breeding wading birds. We suggest that the best feeding conditions for breeding snipe will be provided by keeping the upper soil soft enough for them to probe in but without reducing soil macroinvertebrate biomass by flooding it beforehand. Optimal conditions for breeding lapwings and redshank will probably be provided by creating a mosaic of unflooded grassland, winter‐flooded grassland and shallow pools.
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Effects of egg size and parental quality on lapwing Vanellus vanellus chick survival were studied in southwestern Sweden over 6 years. Chicks from large eggs were heavier at hatching and survived significantly better than those from small eggs. To control for the confounding effect of parental quality on egg size and chick survival, we performed a cross-fostering experiment during 2 years, exchanging clutches between nests with large and small eggs. In control clutches, chicks from large eggs survived better than those from small eggs, but we found no significant difference in chick survival between exchanged clutches. Thus, egg size did not affect chick survival independently of parental quality. Fledging success increased with parental age and/or experience, and with female body mass. Hence, both egg size and parental quality affect chick survival in the lapwing.
Article
During the summer of 1992 we placed wire-mesh exclosures around 13 of 52 Pectoral Sandpiper (Calidris melanotos) nests near Oliktok Point on the North Slope of Alaska. Exclosures were 66-69 cm in diameter, 31-cm tall, and were made of 5 × 10-cm mesh weld-wire with 3-cm mesh chicken wire tops. The 5 × 10-cm mesh size allowed females to enter and exit an exclosure easily, and design of the exclosure provided sufficient anchoring to prevent Arctic fox (Alopex lagopus) from digging under or raising exclosures. Daily survival rate of protected nests (0.982) was significantly greater than that of unprotected nests (0.717). In considering the daily survival rates of protected and unprotected nests, the behavioral responses of Pectoral Sandpipers to exclosures, and the fact that no protected nests were depredated, we conclude that this exclosure was effective under our study conditions. We offer specific considerations for designing exclosures and suggest that exclosures similar to the one we describe may be used to protect other shorebird species.
Chapter
The public, and the government agencies that they influence, are often aroused to the cause of wildlife conservation only after species are seriously endangered. Unfortunately, the protection and restoration of already endangered species is at best an expensive and difficult endeavor; at worst, it can be a futile one. Thus, there is no question that preventive measures are the best ones. This is certainly the case in conservation efforts directed toward shorebirds.
Article
This paper investigates factors influencing the intraspecific variability of incubation periods in Avocets Recurvirostra avosetta. The length of the incubation period of 278 clutches ranged from 19 to 34 days with an average of 23.1 days. Incubation period was influenced by clutch size. There was a seasonal decrease in incubation period resulting in a difference of 1.7 days between the earliest and the latest clutches. The seasonal trend could not be explained by ambient temperature. No relationships could be found between incubation period and colony size, nest density, or habitat. There were significant positive correlations between incubation period and bill length and foot length of the neonates. The possibility that incubation period is influenced by a trade-off between egg and chick mortality rates and embryonic and chick growth rates is discussed.
Article
The populations of farmland birds in Europe declined markedly during the last quarter of the 20th century, representing a severe threat to biodiversity. Here, we assess whether declines in the populations and ranges of farmland birds across Europe reflect differences in agricultural intensity, which arise largely through differences in political history. Population and range changes were modelled in terms of a number of indices of agricultural intensity. Population declines and range contractions were significantly greater in countries with more intensive agriculture, and significantly higher in the European Union (EU) than in former communist countries. Cereal yield alone explained over 30% of the variation in population trends. The results suggest that recent trends in agriculture have had deleterious and measurable effects on bird populations on a continental scale. We predict that the introduction of EU agricultural policies into former communist countries hoping to accede to the EU in the near future will result in significant declines in the important bird populations there.
Book
1. Introduction 2. Estimation 3. Hypothesis testing 4. Graphical exploration of data 5. Correlation and regression 6. Multiple regression and correlation 7. Design and power analysis 8. Comparing groups or treatments - analysis of variance 9. Multifactor analysis of variance 10. Randomized blocks and simple repeated measures: unreplicated two-factor designs 11. Split plot and repeated measures designs: partly nested anovas 12. Analysis of covariance 13. Generalized linear models and logistic regression 14. Analyzing frequencies 15. Introduction to multivariate analyses 16. Multivariate analysis of variance and discriminant analysis 17. Principal components and correspondence analysis 18. Multidimensional scaling and cluster analysis 19. Presentation of results.
Article
Most Holarctic waders lay determinant clutches of four eggs, but the adaptive significance of this clutch size remains unresolved. The incubation-limitation hypothesis posits that waders cannot successfully incubate larger clutches, but this hypothesis has not received widespread acceptance. In this review, I show that clutch enlargement invariably leads to greater rates of nest predation, egg damage, and hatching failure, and that these three costs of incubation are sufficient to limit clutch size among most species of waders.
Article
Artificial birds' nests containing 2 eggs were placed in 5 study plots (area 4 ha) at densities of 1 to 4 nests ha-1 and exposed for short periods (1-3 days) to predation, mainly by Corvus corone cornix L. and Larus argentatus Pont. Predation rates were high (75 to 96% on average in 6 experiments) and positively correlated with nest density in 4 plots. In the fifth plot, individuals of Vanellus vanellus L. and, to a lesser extent, Numenius arquata L. were present and defended their ranges against predators. A significantly lower frequency of predators over this study plot than the others was recorded, and the rate of predation (26%) on the artificial nests in this plot was also significantly lower. The importance of this result for some current hypotheses about the role of predation in bird communities is pointed out. /// Искусственные птичьи гнезда с 2 яйцами помещались на 5 опытных участков (площадью 4 га) по 1-4 гнезда/га, и в течение 1-3 дней их осталяли открытыми для хищников, преимущественно Corvus corone cornix L. и Larus argentatus Pont. Активность хищников была высокой (75-96% в средним из 6 опытов) и прямо зависела от плотности гиезд уа 4 участках. На пятом участке обитали Venallus vanellus L. и в меньшем количестве Numenius arquata L. которые защищали свои территории от хищников. На этом уастке наблюдалась значительно более низкая численность хищников, чем на других, и количество разрушенных искусственных гнезд составило 26%. Подчеркивается значение этих опытов для некоторых рабочих о роли хищников в комплексах птиц.
Article
Biologists often mark the position of nests with canes. In a series of experiments, it was shown that crows (Corvus corone) readily found chickens' eggs in well-concealed artificial nests marked with a short cane 5 m away. The conclusion is that the use of markers near nests may lead to greater egg predation than would occur in natural situations.
Article
Depredation of sea turtle nests by raccoons (Procyon lotor) can hinder management attempts to increase recruitment of turtle hatchlings. We tested 3 techniques for their effectiveness in reducing raccoon predation on turtle nests. During 1993-94, direct comparisons of lethal removal, nonlethal conditioned taste aversion (CTA), and nest screening were conducted at Canaveral National Seashore (CNS), Florida. Lethal removal of 215 raccoons, at a level of about 50% of the population using the barrier beach, was not effective at reducing nest depredation. Nonlethal use of estrogen-laced eggs to induce conditioned taste aversion had no significant effect on nest depredation rate. Nest screening was the only treatment that significantly reduced nest depredation. Nest screening was labor-intensive and more expensive than lethal removal and CTA, but maintained raccoons as part of the coastal ecosystem while affording protection to sea turtle nests.
Article
(1) Daily survival rates of nests with respect to predation are referred to as P-values, trampling survival rates are expressed as 'standardized trampling values', estimated as daily survival rates at an exposure of one grazing animal ha-1 (2) P-values were lower during laying than during incubation. P-values in hiddennesting species are higher than in open-nesting species. P-values are not constant, but are highest in the middle of the nesting season. P-values differ between regions and years, and are positively correlated with densities of voles, Microtus sp. In years following a collapse of vole populations, ground predators switch more to birds' nests. (3) Standardized trampling values are independent of cattle densities and field size, hence the probability of surviving is a simple function of stock density and days exposure. (4) A renesting model is presented, to estimate nesting success per pair, taking renesting into account, based on P-values and trampling values. The model enables the testing of the effects of different management schemes on nesting success.
Article
With its umbrella of provisions, the U.S. Endangered Species Act ( ESA ) provides critical protection to threatened or endangered wildlife. It provides minimal guidance, however, on identifying taxa worthy of conservation, lacks guidelines for resolving endangered species conflicts, and subsequent recovery programs often focus on the species rather than the ecosystem. These deficiencies are exemplified by the recovery program for the San Clemente Loggerhead Shrike ( Lanius ludovicianus mearnsi ) and the recent proposed rule to grant federal protection to one of its predators, the island fox ( Urocyon littoralis ). Recovery actions that have included euthanasia of foxes have likely contributed to a 40–60% decline in the population size of the San Clemente Island fox ( U. l. clementae ), a subspecies listed by the state of California as threatened. The U.S. Fish and Wildlife Service proposes to list four other subspecies of the island fox as endangered but excludes the San Clemente Island fox and the sixth and last subspecies, the San Nicolas Island fox ( U. l. dickeyi ), ignoring their evolutionary distinctness and the recent decline in population size of U. l. clementae. Using published morphological and genetic information, we show that the shrike's current taxonomic and legal status should be reevaluated. We also reexamine the current recovery program for the shrike and conclude that the implementation of the ESA's provisions to protect the shrike was species-centric. The shrike recovery program is primarily centered on two approaches: the release of captive-bred shrikes and control of native and non-native predators. The predator control program has contributed to the endangerment of the distinct San Clemente Island fox. Given that five of the six fox subspecies face extirpation, the proposed rule to list only four of the six as endangered is inadequate. This endangered-species conflict might have been avoided through a more balanced ecosystem approach that considers the ecological role of all native taxa and strives to enhance habitats critical to both the shrike and the fox. Resumen: Con su normatividad general, el Acta de Especies en Peligro de E. U. A. ( 1973 ) ( AEP ) proporciona protección decisiva a vida silvestre amenazada o en peligro. Sin embargo, proporciona una orientación mínima para identificar taxones merecedores de conservación y aumenta las directrices para resolver conflictos con especies en peligro, y los subsecuentes programas de recuperación a menudo enfocan en la especie y no en el ecosistema. Estas deficiencias están ejemplificadas por el programa de recuperación para el alcaudón ( Lanius ludovicianus mearnsi ) y la recientemente propuesta ley para otorgar protección federal a uno de sus depredadores, el zorro ( Urocyon littoralis ). Las acciones de recuperación, que han incluido la eutanasia de zorros, probablemente han contribuido a la declinación del 40–60% de la población del zorro de San Clemente ( Urocyon l. clementae ), una subespecie listada como amenazada por el estado de California. El Servicio de Pesca y Vida Silvestre de E. U. A. propone listar otras cuatro subespecies de Urocyon littoralis como en peligro pero excluye a Urocyon l. clementae y la sexta y última subespecie, U. l. dickeyi, ignorando su singularidad evolutiva y la reciente declinación de la población de Urocyon l. clementae. Utilizando información morfológica y genética publicada, mostramos que el estatus taxonómico y legal de Lanius ludovicianus mearnsi deben ser reevaluados. También reexaminamos el actual programa de recuperación para Lanius ludovicianus mearnsi y concluimos que la instrumentación de las disposiciones de AEP para proteger a la especie son especie-céntricas. El programa de recuperación de Lanius ludovicianus mearnsi se centra principalmente en dos tratamientos: la liberación de alcaudones criados en cautiverio y el control de depredadores nativos y no nativos. El programa de control de depredadores ha contribuido a poner en peligro a Urocyon l. clementae. Dado que cinco de las seis subespecies de zorro encaran la extirpación, la propuesta ley de listar solo cuatro de las seis como en peligro es inadecuada. Este conflicto de especies en peligro pudo haberse evitado con un enfoque ecosistémico más balanceado que considere el papel ecológico de todos los taxones nativos y se esfuerce por incrementar los hábitats críticos tanto para el alcaudón como para los zorros.
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The efficacy of protecting loggerhead Caretta caretta turtle nests from red fox Vulpes vulpes predation was examined at Dalyan beach, Turkey. Twenty-five nests were protected using individual wire mesh grids. Predation occurred at 63% of the 88 unprotected control nests. In contrast, no protected nests were predated. As a consequence, hatching success was significantly higher at protected nests than at control nests. The feasibility of adopting wire mesh grids as a routine method for turtle nest conservation is evaluated.
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Reports of nesting success that do not take into account the time span of observation for each nest usually understate losses, and sometimes the error can be very large. More than a decade ago I pointed out this problem and proposed a way of dealing with it (Mayfield 1960:192-204; 1961). Since that time many field students have used the method, and it has proved es- pecially helpful in combining fragments of data from many sources, as in the North American Nest-record Program at Cornell University. However, not every published report shows awareness of the problem, and letters of in- quiry have shown that some people are deterred from dealing with it because of difficulty with details. Therefore, I offer these further suggestions to sim- plify the procedure as much as possible. THE PROBLEM All nests are not found at the very start. Indeed, most nests of small open- nesting birds are not found until incubation is well under way or until the young have hatched. The observed success in such a sample will be greater than the true nesting success of the species. The shorter the time span of observations, the less the observed losses; that is, nest mortality-loss by destruction or desertion-is a function of time. Since nearly all field studies contain a mixture of nests found early and late, as customarily reported they show nesting success higher than real- ity; but the amount of error is indeterminable because the time each nest entered the sample is not reported. For precise analysis of mortality and sur- vival, it is not enough merely to count nests, eggs, and young. The elapsed time of the observations must also be considered. To illustrate the main difficulty, suppose you found a series of nests when incubation was far advanced. Hatching success would be nearly 100%; and in nests containing large young when found, fledging success would be nearly 100%. Yet you would hesitate to present these figures because it is plain that not enough time elapsed for many accidents to befall. In this extreme case the pitfall is obvious, but in a mixed bag of data, this kind of error may slip through unnoticed. What you are trying to determine is the nesting success of a population. Ideally you would like to find all the nests started by the birds in that pop- ulation, watch all these nests from their beginnings, and observe everything that happened up to the fledging of young. Usually this is impossible and you have to settle for a good deal less, namely, a sample that is anything but 456
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Coastal pastures and other wet grasslands are important but decreasing breeding habitats for many waders (Charadrii). Since loss of suitable habitat is a major reason for population declines, protection and restoration of these habitats is crucial. Reduction of the often high rate of nest predation is a potentially important tool in future conservation work. Here, we focus on predators’ use of raised structures in the landscape when searching for prey. Hooded crows (Corvus corone cornix) use man-made structures such as stone walls and barbed wire fences when foraging on coastal pastures in SW Sweden. However, few studies have examined wader breeding success in relation to man-made structures, and the extent to which such structures are used by searching nest predators. We measured the spatial distribution and rate of predation on wader nests in relation to such structures. Crows spent more time at or near man-made structures than expected by chance, but we found no significant difference in nest predation relative to distance from man-made structures. However, wader nests were placed farther away from man-made structures than expected by chance in two out of three years. Waders thus tend to avoid breeding close to man-made structures, which therefore reduce the suitable breeding area and probably also the local wader population size.