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Direct human-caused mortality of birds: Improving quantification of magnitude and assessment of population impact
Abstract
Hundreds of millions to greater than one billion North American birds are directly killed each year by human stressors, including collisions with man-made structures, predation by feral and pet cats, intentional and accidental poisoning, and pollution. Because these causes of mortality are increasingly abundant and because some result in large bird die-offs, they have received both increased scientific attention and general media coverage. However, quantifying bird mortality remains imprecise and methods to assess whether these losses cause important biological impacts remain underdeveloped. If local mortality studies followed rigorous design and sampling schemes, allowing comparison of data and scaling up of mortality estimates to broad regions, this could lead to improved analyses. Several analytical techniques - including hierarchical and population models - show potential for improving quantification of anthropogenic mortality of birds and inference of population-level effects. Results arising from improved study designs and analytical techniques will more effectively inform decision making about policies and regulations aimed at reducing avian mortality and minimizing population impacts.
... We then examine the extent to which spatially explicit indices of threat vulnerability correlate with breeding population trends for 103 Afro-Palaearctic migratory birds. We assess cumulative exposure to risk by grouping threats according to whether they pose direct mortality threats to birds (Loss et al., 2012e.g., overharvesting, collision risks), threats mediated through diffuse impacts of environmental change (habitat degradation, e.g., through loss of foraging resources) or the potential for both (climate change, e.g., extreme events, decline in resource availability). By grouping the threats in this manner, we aim to isolate elements of anthropogenic change that pose immediate survival threats from those that may pose more chronic and indirect threats, and from climate threats, which may pose a complex combination of direct and indirect threats and potential benefits. ...
... For species that make nocturnal movements, bird-building collision risks are exacerbated by artificial light at night (Lao et al., 2020;Van Doren et al., 2017); we mapped this using the Defense Meteorological Program Operational Line-Scan System (DMSP-OLS) Nighttime Lights Time Series (NOAA, 2013). We used human population density (CIESIN, 2018) as an index to capture other direct anthropogenic mortality risks (Anadón et al., 2010;Kerr & Currie, 1995;McKee et al., 2004) including disturbance (Gill, 2007;Mallord et al., 2007) and invasive species (Newbold et al., 2015;Spear et al., 2013) -in particular the impacts of domestic and feral cats (Felis catus) (Aegerter et al., 2017;Loss et al., 2012Loss et al., , 2013b. ...
... Bird mortality due to powerline collision or electrocution can occur at rates sufficient to have population-level effects (Bernardino et al., 2018;Loss et al., 2012;Schaub et al., 2010), and bring about changes in migratory behaviour (Palacín et al., 2017). To map overhead powerlines we combined World Bank (World Bank, 2017) and ...
Migratory species rely on multiple ranges across the annual cycle, rendering them vulnerable to a wide range of spatially disparate anthropogenic threats. The spatial distribution of these threats will strongly influence the magnitude of their population‐scale effects, but this has not been quantitatively assessed for most species. Europe, Central Asia, Western Asia, Africa. Modern. Aves. We combined remote‐sensed data and expert opinion to map 16 anthropogenic threats relevant to migratory birds across Europe, Africa and the Middle East – including the first spatially‐explicit pan‐continental assessment of relative hunting pressure. By combining the resulting composite threat maps with species range polygons and morpho‐behavioural traits‐based weightings (reflecting relative threat susceptibility), we created species‐specific risk maps for 103 Afro‐Palaearctic migratory birds breeding in Europe and evaluated how spatial threat vulnerability relates to long‐term population trends. We found that greater vulnerability to direct mortality threats (including hunting pressure, infrastructure and nocturnal lights), especially in the non‐breeding season, is associated with declining bird population trends. Our results emphasize the importance of spatially explicit approaches to quantifying anthropogenic drivers of population declines. Composite risk maps represent a valuable resource for spatial analyses of anthropogenic threats to migratory birds, allowing for targeted conservation actions.
... Despite having an advanced visual system, collisions against anthropogenic structures (eg, commercial and residential buildings) is among the most frequent causes of wild bird mortality, second only to cat predation. [12][13][14][15] A major reason for such frequent collisions is the increasing popularity of translucent window glass, which is not only aesthetically pleasing but also contributes to the health and well-being of humans. 16 Glassrelated collisions are estimated to be responsible annually for 365-988 million bird deaths in the United States alone 17 and 16-42 million bird deaths in Canada. ...
... 26,32 However, fatal collisions occur worldwide in cities and rural areas, with all window sizes and shapes being susceptible to bird collisions, regardless of the time of day, season, or weather conditions. 14,17,[33][34][35] For this study, the exact time of day in which an accident occurred was not recorded for most of the carcasses received. Although nighttime lighting is frequently cited as a factor contributing to building collisions, few evidence-based assessments have been conducted. ...
Birds are among the most visually proficient group of animals on the planet; however, their inability to visualize and discriminate translucent glass structures results in an extreme number of deaths worldwide from high-speed collisions. Despite reports of avian glass collisions in North America, only a few studies have been developed to understand this problem in South America, and none evaluated radiographic and postmortem findings. One hundred cadavers were examined radiographically and postmortem, and data from 186 collision reports were analyzed for seasonality (website and manual reports and cadavers). A total of 34 different species of birds within 22 families were evaluated for this study, with the rufous-bellied thrush (Turdus rufiventris; n = 12), eared dove (Zenaida auriculata; n = 12), and ruddy ground dove (Columbina talpacoti; n = 10) being the most common species. Only 6 (27.7%) migratory species were reported: Sick's swift (Chaetura meridionalis), small-billed elaenia (Elaenia parvirostris), Black Jacobin (Florisuga fusca), Great kiskadee (Pitangus sulphuratus), Double-collared seedeater (Sporophila caerulescens), and Creamy-bellied thrush (Turdus amaurochalinus). Males (51) were more frequently reported than females (5), and 50.1% of the males had active gonads. Sex was unable to be determined in 44 birds. The most common radiographic lesion, noted in 16 of 82 (19.5%) animals, was loss of coelomic definition, suggestive of hemorrhage. Prevalent postmortem findings included skull hemorrhages (58/75, 77.3%) and encephalic contusions (47/73, 64.4%), followed by coelomic hemorrhages (33/81, 40.7%). Most of the window collisions (61/186, 32.8%) occurred during spring, the most common breeding season of avian species in Brazil. Cranioencephalic trauma was identified as the primary cause of mortality associated with birds flying into glass windows. Migration does not appear to be the main predisposing factor for window collisions by birds in Brazil. Increased activity and aggression related to breeding season, especially in males, may be a more important predisposing factor for window collision accidents.
... Understanding differences in species' vulnerability to building collisions is central to predicting potential population-level effects of this source of mortality (Loss et al. 2012, Cusa et al. 2015, Elmore et al. 2020), but species with primarily western North American distributions comprised only 4 of 100 species reported to be more vulnerable to collision mortality in the United States (Loss et al. 2014, Elmore et al. 2020. Broad-scale analyses suggest that life history characteristics such as nocturnal migration, insectivory, and preference for forested habitat are most commonly associated with increased vulnerability to collisions (Arnold and Zink 2011, Wittig et al. 2017, Elmore et al. 2020). ...
... Further, many continentally distributed bird species (e.g., Swainson's Thrush [Catharus ustulatus]) include distinct western populations or subspecies due to divergent migratory routes, molting schedules, behaviors, and ecological requirements (Kelly and Hutto 2005, Rohwer and Irwin 2011, Delmore et al. 2012. The potential for reproductive isolation, cryptic species, or discrete populations across east-west divides (Toews andIrwin 2008, Rohwer andIrwin 2011) further complicates our ability to evaluate population-level consequences of bird-window collisions, in the face of limited data (Loss et al. 2012(Loss et al. , 2015. ...
Bird–window collisions are a leading cause of direct anthropogenic avian mortality, yet our state of knowledge regarding this threat relies heavily on eastern North American studies. Seasonal patterns of collision mortality may differ along the Pacific coast, and western North American species remain understudied. We therefore surveyed a stratified random sample of 8 buildings for collisions at the University of British Columbia, Vancouver, Canada over 45-day periods during 2 winters, 1 spring, 1 summer, and 1 fall season between January 22, 2015 and March 15, 2017. After accounting for the rate of scavenging and efficiency of observers in finding carcasses, we estimated that 360 collision fatalities (95% CI: 281–486) occurred over 225 days of collision monitoring. Collision mortality was highest in fall, but in contrast to most published research, collision mortality was intermediate in both winter and spring and was lowest in summer. In winter 2017, we performed point-count surveys to assess whether individual species are disproportionately vulnerable to collisions when accounting for population size and found that the Varied Thrush (Ixoreus naevius) was 76.9 times more likely to collide with buildings, relative to average species vulnerability in winter. To our knowledge, this is the first study to report the Varied Thrush as a species that is disproportionately vulnerable to collisions. Further studies are needed to assess the vulnerability of Western North American species and subspecies, and to determine whether similar patterns of seasonal collision mortality are found elsewhere.
... Some anthropogenic threats may not be detectable due to mismatch between all associated cues and the sensory modalities of the animal (Fisher et al., 2006;Serieys et al., 2015), leading to an unavoidable under-response to risk. This failure to detect risk is responsible for birds colliding with windows, fish consuming toxic plastics, and a range of other unintended phenomena (Loss et al., 2012). In other cases, anthropogenic threats are designed to be undetectable: advances in hunting technology have not only made humans dramatically more lethal than non-human predators (Darimont et al., 2015), but in many cases also serve to minimize the prey's ability to detect the hunter. ...
... Many anthropogenic cues are only associated with a threat in certain contexts, making them unreliable indicators of • Animal collides with window glass (Loss et al., 2012) • Animal consumes poisons/toxins (Serieys et al., 2015) • Animal does not detect boat cue decoupled in space from fishing equipment (Meekan et al., 2018) • Animal does not substantially avoid or anticipate retaliatory killing (Loveridge et al., 2017) Assessment mismatch • Unreliability of cue; may be associated with both lethal and non-lethal human activity (Thouless et al., 1991;Meekan et al., 2018) • Animal is attracted to resource subsidies increases vulnerability to harvest or accidental death (Johnson et al., 2020) • Toxins present olfactory trap for a foraging animal (Savoca et al., 2017) Response mismatch • Novelty of cue; does not resemble risk cues encountered in evolutionary history ...
Human activity has rapidly transformed the planet, leading to declines of animal populations around the world through a range of direct and indirect pathways. Humans have strong numerical effects on wild animal populations, as highly efficient hunters and through unintentional impacts of human activity and development. Human disturbance also induces costly non-lethal effects by changing the behavior of risk-averse animals. Here, we suggest that the unique strength of these lethal and non-lethal effects is amplified by mismatches between the nature of risk associated with anthropogenic stimuli and the corresponding response by wild animals. We discuss the unique characteristics of cues associated with anthropogenic stimuli in the context of animal ecology and evolutionary history to explore why and when animals fail to appropriately (a) detect, (b) assess, and (c) respond to both benign and lethal stimuli. We then explore the costs of over-response to a benign stimulus (Type I error) and under-response to a lethal stimulus (Type II error), which can scale up to affect individual fitness and ultimately drive population dynamics and shape ecological interactions. Finally, we highlight avenues for future research and discuss conservation measures that can better align animal perception and response with risk to mitigate unintended consequences of human disturbance.
... The difference between the number of entries (births and immigration) into and exits (deaths and emigration) from a population over determines temporal change in abundance (Pradel, 1996;Williams, Nichols, & Conroy, 2002). Vital rates, like survival, may be affected by environmental conditions (Amundson & Arnold, 2011;Aubry et al., 2013), anthropogenic factors (Arnold & Zink, 2011;Loss, Will, & Marra, 2012), and demographic stochasticity (Lande, 1993). Vital rates are also influenced by a population's evolutionary history (Koons, Pavard, Baudisch, & Metcalf, 2009;Stearns, 1992). ...
... Successive years of declining abundance, from anthropogenic disturbance or other causes, can initiate management actions that are directed at specific vital rates to induce population-level change in abundance (Loss, Will, & Marra, 2012). The most common example is the use of take regulations to regulate annual survival (Runge & Boomer, 2005). ...
Abstract Population change is regulated by vital rates that are influenced by environmental conditions, demographic stochasticity, and, increasingly, anthropogenic effects. Habitat destruction and climate change threaten the future of many wildlife populations, and there are additional concerns regarding the effects of harvest rates on demographic components of harvested organisms. Further, many population managers strictly manage harvest of wild organisms to mediate population trends of these populations. The goal of our study was to decouple harvest and environmental variability in a closely monitored population of wild ducks in North America, where we experimentally regulated harvest independently of environmental variation over a period of 4 years. We used 9 years of capture–mark–recapture data to estimate breeding population size during the spring for a population of wood ducks in Nevada. We then assessed the effect of one environmental variable and harvest pressure on annual changes in the breeding population size. Climatic conditions influencing water availability were strongly positively related to population growth rates of wood ducks in our study system. In contrast, harvest regulations and harvest rates did not affect population growth rates. We suggest efforts to conserve waterfowl should focus on the effects of habitat loss in breeding areas and climate change, which will likely affect precipitation regimes in the future. We demonstrate the utility of capture–mark–recapture methods to estimate abundance of species which are difficult to survey and test the impacts of anthropogenic harvest and climate on populations. Finally, our results continue to add to the importance of experimentation in applied conservation biology, where we believe that continued experiments on nonthreatened species will be critically important as researchers attempt to understand how to quantify and mitigate direct anthropogenic impacts in a changing world.
... One of the earliest documented influences of anthropogenic light at night was its ability to attract or repel wildlife (positive and negative phototaxis) (Longcore and Rich 2004). Attraction and repulsion underly the most conspicuous of adverse impacts of artificial light at night, including mortality of birds at buildings and other tall structures such as communication towers and light houses (Longcore et al. 2012, Loss et al. 2012, attraction of hatchling sea turtles and repulsion of nesting females , and the mortality of insects attracted to lights ). ...
1. Systematic Map of Effects of Light from LEDs at Night on Terrestrial Wildlife
2. Relative Importance of Intensity and Spectrum of Artificial Light at Night in Disrupting Behavior of a Nocturnal Rodent
3. A Database of Species Visual Responses to the Spectral Distribution of Light
4. Assessing and Mitigating Taxon-Specific Light Pollution Impacts from Roadway Lighting Projects
5. Guidance for Evaluating and Mitigating Impacts to Sensitive Species from Artificial Light at Night in Caltrans Projects
... Citizen science programs have already substantially raised the profile of this issue, and their actions have informed legislation. For example, based on the efforts of its citizen driven Project Safe Flight program, New York City Audubon successfully advocated for an amendment to New York City's building code requiring that bird friendly materials be used in new buildings (Liao 2019). ...
Bird-window collisions (BWCs) are a major threat to avian populations, annually causing up to one billion bird deaths in the US alone and untold numbers of fatalities worldwide. Until recently, there has been limited institutional and governmental recognition of this issue and few coordinated, national-level efforts to address it. To fill this need, citizen-science campaigns have stepped in to generate scientific information about BWCs, raise public awareness, and advocate for policy and actions to reduce collisions. We review the BWC issue and showcase how citizen-science programs in multiple countries have achieved these outcomes. Additional citizen-driven successes in addressing BWCs are possible if key constraints are overcome, including funding limitations and challenges of proactively engaging stakeholders who can reduce BWCs at scale. Addressing this global conservation issue will also require building upon the recent increase in attention to BWCs by government agencies, nongovernmental organizations, commercial entities, and professional scientists.
... Besides carcasses searches, it is noteworthy that the majority of the studies also included carcass persistence and detection trials, which are essential for the adjustment of the bird fatality estimates Bernardino et al., 2013). However, the diversity of used methods (e.g., frequency of sampling, width of search area, number and type/size of carcasses used in the trials), and the lack of adequate approaches in some cases, makes it difficult to obtain reliable estimates of the number of bird fatalities/year in the entire line, as well as comparing results across different projects (Huso, 2019;Loss et al., 2012). ...
Bird mortality by collision is one of the major biodiversity impacts of transmission power lines. The European Union legislation determines that overhead power lines subject to Environmental Impact Assessment (EIA) procedure should be monitored at post-construction to confirm the predicted impacts, and evaluate the effectiveness of the implemented mitigation measures. In light of the frequent calls to improve study design and quality of field data in EIA context, we reviewed a decade (2004-2015) of post-construction monitoring practices adopted in Portugal for assessing the impacts caused by transmission lines (150-400 kV) on birds and evaluating wire-marking effectiveness to reduce collisions, the main mitigation measure. We reviewed 31 monitoring programs to (i) characterize the practices (field surveys and its methods) adopted, (ii) identify specific objectives behind field surveys, (iii) detect the main methodologic limitations, and (iv) provide guidelines to improve future bird monitoring programs. Overall, reviewed studies contained significant field efforts, always including bird carcass surveys (very often with trials to assess carcass detection and persistence biases) to estimate mortality rates and often including surveys to determine bird abundance and the frequency of flights crossing the wires. However, we also found limitations, namely (i) a frequent lack of clear reporting of specific objectives behind field surveys, hindering the usefulness of data collected, (ii) a dominance of poor methodological approaches evaluating indirect impacts and wire marking effectiveness, and (iii) the (less frequent) use of inadequate protocols and a lack of standardization, hindering comparability across studies. To overcome these limitations, we propose a methodological framework and specific recommendations to improve current practices for measuring the impacts of new transmission lines on birds and evaluating the effectiveness of wire-marking to reduce collisions. Although developed for the Portuguese EIA context, these recommendations are likely applicable to many other countries.
... proportion of vertebrate mortality results from direct anthropogenic sources (e.g., collisions with man-made structures or traffic casualties), and accurate mortality quantification is essential to inform policy decisions. The use of mortality estimates to assess whether a threat has a biologically important impact is critical for conservation [3]. Concerns about anthropogenically caused climate change have resulted in running out of fuel, and the development of renewable energy sources, mainly wind farms and solar technologies [4,5]. ...
Wind farms are an alternative energy source mitigating environmental pollution. However, they can have adverse effects, causing an increase in mortality for wildlife through collision with wind turbines. The aim of this study was to investigate the risks of bird collisions with wind turbines linked to species-specific variables. For this purpose, we have analysed the dead birds involved in wind farm collisions that were admitted to two rescue centres in Spain over a period of 16 years (2001–2016; full dataset: n = 3130). All the birds analysed in this study were killed by turbines in wind farms. We performed two linear models using all species and a reduced dataset (bird of prey and passerine having more than four collisions) that included group, seasonal movements, flight type, length, and the number of pairs for the Spanish and European populations. The coefficients and the percent of variance explained by each relevant variable were determined in the models and the real values were compared with predicted values to visualise the goodness of fit. We found that the flight type was the most important variable explaining 35% of the total variability for the model including all species and 29% for the reduced dataset respectively, followed by seasonal movement type (4%/17% respectively) and the Spanish population (4%/6%). Subsequent analyses suggested that species with hovering, song-flights and active soaring flights are more susceptible to collisions with wind farms, and that species showing partial migration have a significant peak of collisions across spring and autumn. The estimated species-specific collision index can help in modelling the theoretical risk of collision with wind turbines, depending on the species existing in the area and their predicted values of vulnerability, which is linked to flight types and seasonal movements.
... Fiber-optic cable and other lines used in communications can be constructed in a manner similar to powerlines and thus can have similar collision risk. Guy wires used to support communication towers (see Fig. 14.3) have been shown to have collision risk for landbirds (Gehring et al., 2011;Loss et al., 2012) and seabirds like the Newell's Shearwaters (Travers et al., n.d.) and the critically endangered Black-capped Petrel (Pterodroma hasitata) on the island of Hispaniola in the Caribbean (Brown et al., 2013). Light attraction likely played an exacerbating role in the documented collisions for the Black-capped Petrel, but regardless, observations from Hispaniola indicate tower guy wires should be considered a threat to seabirds. ...
Avian collisions with human infrastructure are one of the top anthropogenic causes of mortality in landbirds and waterbirds, killing hundreds of millions of birds annually in North America alone. Researchers have also begun to document powerline collisions across several groups of seabirds and have reported that powerline collisions can have population-level impacts. Avian collisions often result when artificial light causing attraction or disorientation increases collision risk with buildings, towers, boats, and offshore oil platforms when they are lighted. This type of collision risk can be eliminated or greatly reduced when lights are man-aged to prevent avian issues, which is discussed from a seabird perspective in Chapters 6 and 13. Collisions occur independently of artificial lights when birds fly at infrastructure that is difficult to detect and or avoid such as windmill blades (see Chapter 7), communication towers, and various wires including guy wires on communication towers, communication wires, and powerlines. Powerlines are of particular concern for avian conservation because of their immense footprint on the landscape and the high levels of mortality documented at subsampled sections of powerlines. We review case studies of endangers seabird powerline collisions that indicate that seabird powerline collisions are under detected and threatening seabird populations. Lastly, we discuss methods for rapid collision assessment and collision reduction tools from a seabird perspective.
... Responses to these stressors can range from long-term and widespread effects to shorterterm and localized effects and can affect populations, sub-populations and/or individuals. At the individual level, focus is often placed on lethal effects, particularly following acute and extreme stressors such as oil spills, pollution events or severe weather events (Loss et al., 2012;Haney et al., 2014a). Sublethal effects are, however, also relevant and can include but are not limited to changes in behavior, movement or reproductive ecology (Peréz et al., 2010;Eggert and Jodice, 2008;Wilkinson et al., 2019). ...
The northern Gulf of Mexico supports a diverse community of nearshore seabirds during both breeding and nonbreeding periods of the annual cycle and is also a highly industrialized marine ecosystem with substantial levels of oil and gas development particularly in the west and central regions. Stakeholders in the region often assess risk to species of interest based on these differing levels of development. We collected blood samples from 81 adult and 35 chick eastern brown pelicans (Pelecanus occidentalis carolinensis) from 10 colonies across the northern Gulf of Mexico and used these to establish baseline values for hematology and blood biochemistry. We assessed the potential influence of body condition, sex and home range size on hematology and blood biochemistry. We also assessed potential influences of oil and gas activity by considering differing levels of oil and gas development that occur regionally throughout the study area. Although blood analyte concentrations of adults and chicks were often associated with these regional differences, the pattern we observed was not entirely consistent with the differing levels of oil and gas activity across the Gulf, suggesting that regional levels of oil and gas activity around breeding sites may not be the primary drivers of hematology and blood biochemistry. We note that baseline values or reference intervals are not available for other nearshore seabirds that breed in the northern Gulf. Given that exposure and risk may differ among this suite of species based on diet, foraging strategies and life history strategies, similar assessments and monitoring may be warranted.
... Although collisions with vehicles contributed to lower rates of mortality than transmission lines, the total length of highways within grasslands of the region far exceeds the length of transmission lines, and thus is likely to result in greater total mortalities and may have greater effects on bird populations. Several studies have concluded that collision mortality does not significantly impact select bird populations (e. g., Meyer 1978, Thompson 1978, James and Haak 1979, Beaulaurier 1981, Faanes 1987, Alonso and Alonso 1999, but more recent data suggests that collision mortality may in fact have population-level impacts (Schaub and Pradel 2004, Schaub et al. 2010, Loss et al. 2012, especially for bird species of conservation and economic concern (Hobbs 1987, Bevanger 1995, 1998, Janns 2000. Limited data in Canada restricts the confidence in impact estimates to populations, especially for migratory species that encounter collision risk across hundreds of kilometers of their migratory paths throughout the year (Rioux et al. 2013). ...
Electrical transmission line development has been expanding globally by 5% per year, leading to increases in avian collisions with lines. Canadian estimates of transmission line collision mortalities range from 2.5 to 25.6 million birds per year, with the majority of mortalities attributed to collisions with overhead shield wires, and by susceptible birds that are young, large-bodied, with low maneuverability, or in open habitats. In this study, avian mortality was estimated for a ~4900 ha area in the mixed-grass prairie of southeastern Alberta following construction of two major transmission lines. We surveyed seven 500 m transects 7-10 times during both the breeding and migration seasons, where transects were categorized into road (n = 2), transmission line (n = 2), wetland (with transmission lines above; n = 1), or control (n = 2) areas. During the 2016 breeding season (5 May-24 June), we detected 23 mortalities under transmission lines, 7 mortalities beside roads, and no mortalities in controls. In the 2017 spring migration season (31 March-5 May), we detected 24 mortalities under transmission lines, 3 mortalities beside roads, and no mortalities in controls. Mortality rates were adjusted with biases estimated from detectability and scavenging trials. Scavenging rates were high (82% of carcasses were scavenged within 5 days) and detectability of deceased birds was positively related to body size. Overall, linear disturbances within the study area, including 37.7 km of highways and transmission lines, contributed to an estimated 75 deaths/km of linear disturbance during one migration and one breeding season (~50 deaths/km of transmission line and ~25 deaths/km of road; ~1904 bird mortalities total). These findings point to the need for mitigation to reduce bird mortality, thereby minimizing the long-term impact of linear disturbances, such as transmission lines and roads, on associated bird communities.
... According to , habitat loss and degradation represent the greatest threat to bird populations. Still, other factors such as building and window collisions, outdoor domestic cats, and reduced populations of arthropods contribute to widespread declines (Klem 1990;Erickson et al., 2005;Loss et al., 2012;Tallamy and Shriver, 2021). Identifying causal factors responsible for population declines among migratory species is often complicated given that experiences in distinct habitats, spread across hemispheres, can interact to dynamically affect an individual bird's fitness Norris and Marra, 2007 (Walkinshaw, 1983). ...
Populations of many of Nearctic-neotropical migratory birds have declined in the past several decades, recent estimates suggested a dramatic loss of 2.5 billion birds over the past 50 years in North America. Habitat loss and degradation represent a major threat in the tropics. Managed agroecosystems have the potential to mitigate some impacts of land conversion, however, little is known regarding the habitat quality provided by working landscapes in the overwintering range. In this research, we surveyed the migratory bird community in the rapidly expanding oil palm plantations in southern Mexico; and also the declining population of the Wood Thrush (Hylocichla mustelina) inhabiting forest fragments in an agricultural matrix in Costa Rica. We assessed the value of both human-modified habitats by using a combination of demographic, distributional, and individual habitat quality indicators, as well as the relationship of these indicators with environmental characteristics. In the Mexican oil palm plantations, we found that species richness of migratory birds tended to be higher in forest patches than in oil palm, that community assemblages of migratory birds differed between habitats, and that differences in migratory bird abundance were driven by vegetative structure. Specifically, when differences in indicators occurred between oil palm and native forest, most migratory species exhibited indicators of better habitat quality in the native forest. Lastly, we observed, for the first time, territoriality in oil palm plantations and estimated home range sizes for the American Redstart (Setophaga ruticilla), which tended to be smaller than in the native forest. The Wood Thrush population in Costa Rica exhibited an average territory size estimated of 0.71 ha. We were able to determine associations between fragments' characteristics and body conditions, whereby birds in young and more humid fragments exhibited better fitness. Additionally, fragment size alone is probably not the best indicator of habitat quality for Wood Thrushes in Costa Rica. Our results suggest that most species of migratory birds assessed responded positively to forest structure complexity, and that age and sex ratios combined with measures of the physiological conditions, environmental moisture and home range sizes can be used to assess habitat quality for migratory birds overwintering in working landscapes. Importantly, determining a species’ territoriality dynamics, is key when selecting a given indicator of habitat quality for each species due to distributional behavior. Our results also suggest that management strategies that promote forest-like conditions in oil palm plantations can improve the habitat quality in this agroecosystem for declining populations of migratory birds. Additionally, these findings support potential value in variable-sized forest fragments within agricultural areas for the conservation of the Wood Thrushes, and soil humidity could be used as a proximate cue for food availability and ultimately as a habitat quality indicator. Lastly, our results emphasize the importance of determining territoriality dynamics, assessing various habitat indicators, and long-term monitoring, in order to develop effective management measures to improve the conservation value of working landscapes in the Neotropics to mitigate the high rate of habitat loss and degradation, especially considering that habitat availability in the tropics could be limiting migratory bird populations.
... More than 60% of Nearctic-Neotropical migrant species have experienced population declines in recent decades McDonald 1994, Rosenberg et al. 2019), likely due to cumulative effects encountered across the full annual cycle. Contributing factors may include habitat loss and degradation, climate change, pollution, collisions with human-made structures, exotic species, and disease (Loss et al. 2012. Geographically extensive, collaborative partnerships have begun to address these population declines across species' ranges using tracking technology to understand the spatial (e.g., location estimates; patterns of migratory connectivity) and temporal (e.g., migration phenology) dynamics across the full annual migratory cycle (e.g., Stanley et al. 2014. ...
The Cerulean Warbler (Setophaga cerulea) is a declining Nearctic–Neotropical migratory songbird of conservation concern. Implementing full annual cycle conservation strategies to facilitate recovery has been difficult because we know little about the migratory period or strength of migratory connectivity between North American breeding and South American nonbreeding regions. Between 2014 and 2017, we deployed geolocators on 282 males at 14 study sites throughout the species’ range to (1) evaluate the strength and pattern of connectivity between breeding and nonbreeding regions, (2) identify approximate routes and stopover regions, and (3) document migration phenology. We obtained data from 26 birds and observed moderate migratory connectivity overall but documented strong parallel migration for birds breeding in two longitudinally disparate regions. Most (14 of 15; 93%) Appalachian breeders spent the stationary nonbreeding period in the Colombian/Venezuelan Andes, whereas most (5of 7; 71%) Ozark breeders spent the stationary nonbreeding period in Peru/Ecuador. The majority of spring migration (62%) was spent in Central America at multiple stopover locations between Panama and southern Mexico. The 2 migratory periods were approximately equal in duration: 38 ± 2 days (SE) in fall and 42 ± 2 days (SE) in spring. Based on the observed connectivity pattern, conservation of Appalachian breeding populations during the stationary nonbreeding period should focus on forest conservation and restoration in premontane/lower montane forests of Colombia and Venezuela, whereas Ozark breeding population conservation should focus on forest conservation and restoration efforts in Ecuador and Peru. Further conservation efforts are also needed on the breeding grounds, especially for the most sharply declining populations. And finally, conservation of forests used by Cerulean Warblers during stopover periods throughout Central America and southern Mexico, in southeastern United States coastal areas, and in the Mississippi Alluvial Valley will benefit individuals from multiple breeding locations and populations.
... Several studies suggest that power line collision mortality can have significant population-level impacts (Loss et al., 2012;Schaub et al., 2010;Schaub and Pradel, 2004), and red-listed and economically important species are commonly documented casualties (Bevanger, 1995a(Bevanger, , 1998Hobbs, 1987;Janss, 2000). In some cases, there is evidence that power line collision mortality can even lead to changes in migratory patterns and flyways (Palacín et al., 2017). ...
... According to Johnson (2007), habitat loss and degradation represent the greatest threat to bird populations. Still, other factors such as building and window collisions, outdoor domestic cats, and reduced populations of arthropods contribute to widespread declines (Klem, 1990;Erickson et al., 2005;Loss et al., 2012;Tallamy and Shriver, 2021). Identifying causal factors responsible for population declines among migratory species is often complicated given that experiences in distinct habitats, spread across hemispheres, can interact to dynamically affect an individual bird's fitness (Sherry and Holmes, 1995;Norris and Marra, 2007). ...
Habitat loss and degradation represent a major threat to Nearctic-neotropical migratory birds in the tropics. Managed agroecosystems have the potential to mitigate some impacts of land conversion, however, we know little regarding the quality of expanding oil palm plantation habitat for migratory birds in the neotropics. In this study, we used sex and age ratios, body condition, fat deposition, and muscle mass to assess oil palm habitat quality for seven species of migratory songbirds. Specifically, we captured individuals in native forest fragments and oil palm plantations in the state of Tabasco, Mexico, during two winter seasons (2017–2018, 2018–2019), and compared differences in age and sex ratios, and condition indices between habitats. We found that, when differences occurred, most species exhibited indicators of better habitat quality in native forest (older males with higher body condition indices) when compared to oil palm. Our results suggest that age and sex ratios combined with measures of physiological condition can be used to assess habitat quality for Nearctic-neotropical migratory birds overwintering in modified landscapes. Importantly, determining a species’ territorial behavior is key when selecting a given indicator of habitat quality for each species, and in certain cases, more intensive approaches such as estimates of survival, territory size, and food availability may be needed. Our results suggest that management strategies that promote forest-like conditions in oil palm plantations will improve habitat quality for declining populations of Nearctic-neotropical migratory birds.
... Our evaluation allows for a direct comparison to the toll taken by another co-occurring introduced predator, the cat. Such tolls help contextualise the relative predation threats imposed by both species (Loss et al., 2012) Note: Values relating to foxes are from this study. Values relating to cats have been sourced from Legge et al. (2017), , Woinarski et al. (2018), Murphy et al. (2019) and Legge et al. (2020). ...
Aim
Introduced predators negatively impact biodiversity globally, with insular fauna often most severely affected. Here, we assess spatial variation in the number of terrestrial vertebrates (excluding amphibians) killed by two mammalian mesopredators introduced to Australia, the red fox (Vulpes vulpes) and feral cat (Felis catus). We aim to identify prey groups that suffer especially high rates of predation, and regions where losses to foxes and/or cats are most substantial.
Location
Australia.
Methods
We draw information on the spatial variation in tallies of reptiles, birds and mammals killed by cats in Australia from published studies. We derive tallies for fox predation by (i) modelling continental‐scale spatial variation in fox density, (ii) modelling spatial variation in the frequency of occurrence of prey groups in fox diet, (iii) analysing the number of prey individuals within dietary samples and (iv) discounting animals taken as carrion. We derive point estimates of the numbers of individuals killed annually by foxes and by cats and map spatial variation in these tallies.
Results
Foxes kill more reptiles, birds and mammals (peaking at 1071 km⁻² year⁻¹) than cats (55 km⁻² year⁻¹) across most of the unmodified temperate and forested areas of mainland Australia, reflecting the generally higher density of foxes than cats in these environments. However, across most of the continent – mainly the arid central and tropical northern regions (and on most Australian islands) – cats kill more animals than foxes. We estimate that foxes and cats together kill 697 million reptiles annually in Australia, 510 million birds and 1435 million mammals.
Main conclusions
This continental‐scale analysis demonstrates that predation by two introduced species takes a substantial and ongoing toll on Australian reptiles, birds and mammals. Continuing population declines and potential extinctions of some of these species threatens to further compound Australia's poor contemporary conservation record.
... Furthermore, integrating the specific requirements that might explain the foraging distribution of animals and their use of habitat is of major importance in order to define conservation priorities for maintaining habitat quality and their protection over the long-term. Shorebird populations are facing important modifications of their habitats as well as various threats from human activities, either on their breeding, migratory or wintering sitesLoss et al. 2012;. As a consequence, most of largesize shorebird species have an unfavorable conservation status. ...
The bar-tailed godwit (Limosa lapponica) and the black-tailed godwit (Limosa limosa) are two migratory shorebird species that spend the winter on the French Atlantic coast, before to reach regions further north for breeding. These two species share great phylogenetic proximity, and great morphological similarities inherited from a common ancestor from which they recently diverged. In such “closely-related” species, although identical responses are generally observed facing the same environmental conditions, the existence of unique niche properties and specific ecological needs have already been described. It is the case in bar-tailed and black-tailed godwits, which share the same wintering areas, but have a distinct reproduction distribution, breeding respectively in northern Eurasia and Alaska, and from Iceland to eastern Siberia. In France, we mainly observe the subspecies L. lapponica lapponica for bar-tailed godwit, and the subspecies L. limosa islandica for black-tailed godwit, which are present throughout the wintering period (August-April). The subspecies L. lapponica taymyrensis and L. limosa limosa are only present during the migration periods (February-March and August-October). In winter, L. l. lapponica and L. l. islandica mainly use mudflat ecosystems, on which they depend for feeding, as well as marine and coastal marshes, for roosting. Thus, in the Pertuis Charentais (France), they use the same wintering sites and the same functional areas, but exhibit distinct food preferences with a diet dominated by polychaetes worms for the bar-tailed godwit, and bivalves (eg Macoma balthica) and seagrass rhizomes (Zostera noltei) for the black-tailed godwit. Beyond this knowledge, this thesis aims to describe and compare the winter survival strategies of these two species, and especially their spatio-temporal use of habitats. The recent miniaturization of GPS tracking loggers has enabled us to equip individuals of both species to access to their daily and seasonal movements. Such an approach can significantly help to improve our knowledge on the biology of these birds, their dependence on coastal habitats and their link with protected areas / nature reserves. More specifically, we aim to explore the resources selection (prey and habitats) of the two godwit species, in relation to the use of rare roost sites mainly located in nature reserves. Precisely identify birds feeding areas, using GPS position data, allows sampling of potential benthic macrofauna prey, in order to estimate the energy quality of feeding patches and to describe available habitats. In addition, the analysis of bird’s activity on a fine spatial and temporal scale also allows exploring their adaptation to the nycthemeral periodicities, crossed with the use of protected and unprotected areas. Finally, since these birds exhibit a strong sexual dimorphism, it appears interesting to explore the existence of sexual segregation in terms of winter survival strategy. More generally, it is possible to investigate the differences between individuals, or their interactions during feeding in order to test affinities between birds in a gregarious species such as the black-tailed godwit. This work thus provides new key knowledge on the wintering survival strategies of the bar-tailed and the black-tailed godwits, and particularly on their use, in space and time, of different habitats. The results obtained underline both intraspecific and interspecific differences may exist in these two very similar species, which should be considered in future management and conservation measures.
... Furthermore, integrating the specific requirements that might explain the animals' foraging distribution and habitat use is of major importance in order to define conservation actions and priorities aiming to maintain habitat quality and protect birds over the long term. Shorebird populations are facing important modifications of their habitats, as well as various threats from human activities, on their breeding, migratory or wintering sites (Gill et al., 2007;Loss et al., 2012;Pearce-Higgins et al., 2017). As a consequence, most of large shorebird species have an unfavourable conservation status (Pearce-Higgins et al., 2017). ...
Understanding environmental factors underlying animal foraging distribution is of major importance in defining priority conservation actions. During their wintering stage, most shorebirds depend on intertidal areas, as foraging grounds, and on supratidal areas, as high tide roosts. The accessibility of foraging areas and food resources is thus limited, and most wintering shorebirds have to forage whenever mudflats are available, both day and night, to fulfil their daily energetic demands. However, current knowledge of shorebirds’ spatio-temporal use of foraging habitats is often restricted to the daylight period. In that context, we investigated the spatial distribution and habitat selection of wintering black-tailed godwits Limosa limosa islandica, during both the day and night, and in relation to the environmental characteristics. We equipped wintering black-tailed godwits at two different sites on the Pertuis Charentais (Atlantic French coast) with miniaturised GPS loggers. We then tested the hypothesis that godwits feed both during day and night, and show contrasting foraging behaviours and distribution in response to different visual capacities, prey availability, predation risks and human activities. The selection of feeding areas was highly variable according to nycthemeral periodicities, with little change in the habitat types selected. The estimated nocturnal surface of feeding areas were two times smaller than daytime ones, and located closer to the coastline. Moreover, birds largely foraged inside protected areas during the daytime, while most of them foraged outside at night. Finally, godwits with the smallest feeding home ranges stayed inside the Nature Reserves, during both day and night, while the others prospected outside the protected areas more often, preferentially at night.
... Based on our results, it should be assumed that collision risk exists on other Hawaiian Islands where Newell's Shearwaters or Hawaiian Petrels transit past powerlines, at least until proven otherwise. Collision risk should also be considered at other infrastructure that would be similarly hard to detect and avoid at night, such as guy wires on towers (Loss et al. 2012) and windmill blades (Barrios and Rodríguez 2004). Overall, similar risk likely exists for other species of petrels and shearwaters with similar life histories that breed inland of powerlines (Rodríguez et al. 2019) as well as other seabirds, particularly those that fly fast and have reduced maneuverability (Bevanger 1998) such as alcids. ...
ABSTRACT. Powerline collisions have been identified on Kaua'i as a potential contributing factor to the large-scale decline of both
Hawaiian Petrel (Pterodroma sandwichensis) and Newell's Shearwater (Puffinus newelli), but the scale of the powerline collision problem
is unknown. From 2012 to 2020 we conducted observations for seabird powerline collisions across Kaua'i, documented grounded
seabirds, and assessed crippling and environmental biases - both poorly studied facets of powerline collision research. We directly
observed 121 powerline collisions and detected 89 grounded seabirds. While some collisions resulted in birds falling lifelessly out of
the sky, most resulted in seabirds flying or gliding outside of the search area. This means that traditional ground searches would
underestimate total collisions by 78-88% if not accounting for crippling bias. We tested environmental bias by comparing our ability
to conduct searches for grounded birds, "searchability", across multiple variables. Environmental bias resulted in significant reductions
in searchability across regions, environment types, and powerline heights. Furthermore, observed collision rates were significantly higher
at powerlines that had very low to zero searchability. Forty-three percent of observed collisions occurred at unsearchable powerlines
(mainly spanning steep valleys), equating to an estimated 3170 seabird collisions that could not be detected through ground searches.
We detected powerline collisions in every region of Kaua'i, in every environment type, and at all powerline heights monitored. Our
results show that crippling bias and environmental bias are the mechanisms that concealed the geographic distribution of collisions
and the scale of the powerline problem from grounded bird searches, ultimately preventing the detection of thousands of collisions.
The data collected for this study are critical for assessing the scale of seabird powerline collisions and quantifying the biases inherent
in traditional ground searches.
... 38]. These methods of data collection likely lead to under-estimates of actual levels of collisions, often struggling to account for the influences of scavengers, delayed mortalities, or carcass persistence and detectability [39][40][41]. Furthermore, even non-fatal collisions may still negatively impact birds through, for example, increased energetic costs in avoiding hazards [42]. ...
Billions of birds fatally collide with human-made structures each year. These mortalities have consequences for population viability and conservation of endangered species. This source of human-wildlife conflict also places constraints on various industries. Furthermore, with continued increases in urbanization, the incidence of collisions continues to increase. Efforts to reduce collisions have largely focused on making structures more visible to birds through visual stimuli but have shown limited success. We investigated the efficacy of a multimodal combination of acoustic signals with visual cues to reduce avian collisions with tall structures in open airspace. Previous work has demonstrated that a combination of acoustic and visual cues can decrease collision risk of birds in captive flight trials. Extending to field tests, we predicted that novel acoustic signals would combine with the visual cues of tall communication towers to reduce collision risk for birds. We broadcast two audible frequency ranges (4 to 6 and 6 to 8 kHz) in front of tall communication towers at locations in the Atlantic migratory flyway of Virginia during annual migration and observed birds' flight trajectories around the towers. We recorded an overall 12-16% lower rate of general bird activity surrounding towers during sound treatment conditions, compared with control (no broadcast sound) conditions. Furthermore, in 145 tracked "at-risk" flights, birds reduced flight velocity and deflected flight trajectories to a greater extent when exposed to the acoustic stimuli near the towers. In particular, the 4 to 6 kHz stimulus produced the greater effect sizes, with birds altering flight direction earlier in their trajectories and at larger distances from the towers, perhaps indicating that frequency range is more clearly audible to flying birds. This "acoustic lighthouse" concept reduces the risk of collision for birds in the field and could be applied to reduce collision risk associated with many human-made structures, such as wind turbines and tall buildings.
... Understanding demographic processes throughout the full annual life cycle in migratory species is essential for the conservation of migratory species (Marra et al., 2015). For example, direct mortality sources (Loss et al., 2012) are not incorporated into our models. Direct mortality from collision (Bing et al., 2012;Low et al., 2017), poisoning from pesticides and pollutants Barghi et al., 2018), and illegal trapping and consumption (Kamp et al., 2015;Yong et al., 2015) are reported in the region, and are possible cause of declines of these species. ...
... Understanding demographic processes throughout the full annual life cycle in migratory species is essential for the conservation of migratory species (Marra et al., 2015). For example, direct mortality sources (Loss et al., 2012) are not incorporated into our models. Direct mortality from collision (Bing et al., 2012;Low et al., 2017), poisoning from pesticides and pollutants Barghi et al., 2018), and illegal trapping and consumption (Kamp et al., 2015;Yong et al., 2015) are reported in the region, and are possible cause of declines of these species. ...
Population declines in terrestrial bird species have been reported across temperate regions in the world and are attributed to habitat loss, climate change, or other direct mortality sources. North American and European studies indicate that long-distance migrants, common species, and species associated with grasslands and agricultural lands are declining at the greatest rates. However, data from East Asia on avian population trends and associated drivers are extremely sparse. We modeled changes in occupancy of 52 common breeding landbird species in South Korea between 1997-2005 and 2013-2019. Thirty-eight percent of the species showed evidence of declines, and seven of these were declining severely (46-95%). Occupancy of Black-capped Kingfisher (Halcyon pileata) populations have dropped the most precipitously over the study period. Among declining species, long-distance migrants (9/20) and common species (14/20) showed more rapid declines than other groups. Declines of five species were associated with climate change, and two species appeared to be affected by land-cover change. However, causes of change in occupancy of other species (46/52) remains cryptic. Based on our results, we suggest an immediate re-evaluation of species' conservation status and legal protection levels for seven severely declining species in South Korea, and a dedicated survey design and analysis effort for the continued monitoring landbird populations. Because many species exhibiting declines migrate from beyond national boundaries, international collaborations will be required to better quantify population trends across the full annual cycle, and to understand mechanisms for these declines.
... It is estimated that up to 20 billion birds are killed in the United States each year due to direct anthropogenic causes, including collisions with vehicles and various manmade structures, poisoning by oil spills and other contaminants, and predation by domestic cats (Loss et al. 2012(Loss et al. , 2015. A lesser-known threat to birds are hollow metal or PVC (polyvinyl chloride) pipes or posts, which have the potential to kill a large number of birds annually (Ogden 2013;American Bird Conservancy 2016;Malo et al. 2016). ...
... Adaptations of birds for flying, such as reduction of weigh and bone modifications, predispose these animals to suffer from fractures in case of traumatic injuries, as collisions with electric lines, shots, car crashes, among others [1][2][3][4][5]. The anatomical adaptation makes birds more prone to open fractures with exposed bone parts losing vascularization. ...
Anatomic adaptations make birds more prone to open fractures with exposed bone parts losing vascularization. As a result of this exposure, fractures are colonized by different microorganisms, including different types of bacteria, both aerobic and anaerobic, causing osteomyelitis in many cases. For this reason, antibiotic treatment is common. However, carrying out antibiotic treatment without carrying out a previous antibiogram may contribute to increased resistance against antibiotics, especially in migratory wild birds. In this paper, bacterial counts regarding fracture type, bacterial identification and antibiotic resistance have been analyzed in wild birds from wildlife rehabilitation centres in Spain. The results obtained showed that open fractures had higher bacterial counts (CFU/mL) than closed ones. Bacteria in family Enterobacteriaceae, identified were Escherichia spp., Enterobacter spp., Shigella spp., Hafnia alvei, Proteus mirabilis, Leclercia adecarboxylata and Pantoea agglomerans. Other bacteria present in wild birds’ fractures were Aeromonas spp., Enterococcus spp. Bacillus wiedmannii and Staphylococcus sciuri. All species found presented resistance to at least one of the antibiotics used. Wild birds can be implicated in the introduction, maintenance and global spreading of antibiotic resistant bacteria and represent an emerging public health concern. Results obtained in this paper support the idea that it is necessary to take this fact into account before antibiotic administration to wild animals, since it could increase the number of bacteria resistant to antibiotics.
... Comprehensive understanding of the scavenging process and its overall effect on carcass persistence is, therefore, crucial for an accurate assessment of LI-related bird mortality levels and for setting adequate monitoring programmes 19,20 . Carcass size 10,21,22 , season or weather conditions 12,23,24 , biogeographic context and microhabitat 11,17,25 are among the most commonly mentioned factors that influence carcass persistence. ...
Linear infrastructures, such as power lines and roads, are an important source of bird mortality. However, little is known on the potential effect of these infrastructures on local scavenger guilds, their foraging activity and the resulting bird carcass removal patterns. This is an important source of bias in studies aiming to quantify bird fatalities due to linear infrastructures. We used camera-traps to record scavenger identity and persistence patterns of bird carcasses placed close to linear infrastructure and nearby controls in two Mediterranean agricultural regions. We found that linear infrastructure influence on scavenger identity varied depending on the region. Contrary to expectations, linear infrastructure presence had either none or a positive effect on carcass persistence, meaning that carcasses placed within power line or road rights-of-way were not removed faster than the ones placed in controls. We conclude that linear infrastructure effect on vertebrate scavenging patterns is likely to be region-specific, and that reliable correction factors for carcass removal-bias in bird fatality estimates require site-specific experiments to characterize local scavenging processes.
... This study allowed these impacts to be quantified by investigating avian patients and, in doing so, identified the risks faced by avian wildlife and the mortality which results from these. Previous studies have attested that anthropomorphically sourced stressors are the main challenges affecting avian wildlife vitality [26][27][28], and this is consistent with the results of this study. In fact, the preliminary stressors of impact injury, vehicle and rubbish attached, which are all anthropomorphically sourced stressors, accounted for 53% of hospitalisations and 47% of total deaths over a four-year period. ...
Urbanisation exposes avian wildlife to an array of environmental stressors that result in clinical admission and hospitalisation. The aim of this pilot study was to conduct a retrospective analysis of clinical data and characterise this based on categories of stress experienced by avian wildlife patients. The results from this study indicated that impact injuries (n = 33, 25%) and vehicle-related injuries (n = 33, 25%) were the most common occurring preliminary stressors that resulted in the hospitalisation of avian wildlife. The most common outcome of avian patients that suffered from vehicle-related injuries was euthanasia (n=15, 45%), as was avian patients that suffered from impact injuries (n=16, 48%). Immobility (n=105, 61%) and abnormal behaviour (n=24, 14%) were the most commonly occurring primary stressors of avian patients. Finally, trauma (n=51, 32%) and fractures (n=44, 27%) were the most common occurring secondary stressors in avian patients. The most common outcome of all these stressors was euthanasia. This study provided further evidence towards the notion that human and urbanisation related stressors are the main causes of hospitalisation of avian wildlife, but also indicated that birds admitted as a result of human-related stressors are more likely to be euthanised than released. This study also provided a categorisation system for the stressors identified in avian wildlife patients (preliminary, primary and secondary) that may be used to monitor the stress categories of wildlife patients and gain a deeper understanding of the complex notion of stress.
... We cannot rule out general changes in the local abundance of birds, although we do not have data on this. Still, the BACI design is robust for such effects, and the outcome is unaffected by such possibilities as we are solely interested in the interaction term between treatment and period (Loss, Will, & Marra, 2012). ...
As wind energy deployment increases and larger wind‐power plants are considered, bird fatalities through collision with moving turbine rotor blades are expected to increase. However, few (cost‐) effective deterrent or mitigation measures have so far been developed to reduce the risk of collision. Provision of “passive” visual cues may enhance the visibility of the rotor blades enabling birds to take evasive action in due time. Laboratory experiments have indicated that painting one of three rotor blades black minimizes motion smear (Hodos 2003, Minimization of motion smear: Reducing avian collisions with wind turbines ). We tested the hypothesis that painting would increase the visibility of the blades, and that this would reduce fatality rates in situ, at the Smøla wind‐power plant in Norway, using a Before–After–Control–Impact approach employing fatality searches. The annual fatality rate was significantly reduced at the turbines with a painted blade by over 70%, relative to the neighboring control (i.e., unpainted) turbines. The treatment had the largest effect on reduction of raptor fatalities; no white‐tailed eagle carcasses were recorded after painting. Applying contrast painting to the rotor blades significantly reduced the collision risk for a range of birds. Painting the rotor blades at operational turbines was, however, resource demanding given that they had to be painted while in‐place. However, if implemented before construction, this cost will be minimized. It is recommended to repeat this experiment at other sites to ensure that the outcomes are generic at various settings.
... Nocturnal migrants can be attracted by white light which changes their natural behaviour (Gauthreaux and Belser, 2006;Loss et al., 2012). Our previous investigation showed that such attraction is typical of nights with rain, drizzle, high air humidity, and lower cloud cover (Bolshakov et al., 2010(Bolshakov et al., , 2013. ...
Compensation for wind drift in relation to the side-wind velocity and altitude was investigated in Song Thrushes during autumn migration. The birds were recorded at night flying above the prominent leading line of a marine spit which coincided with the general direction of their migration. Among the large size passerine species, Song Thrushes were identified by a combination of five flight characteristics typical only of this species during particular periods of autumn. The thrushes showed different reactions to the crosswinds: complete and partial compensation for the displacement and drift. Under normal visibility, the completeness of compensation depended both on the velocity of the side-wind and altitude. The degree of compensation achieved was reduced with an increase of altitude, regardless of the wind. Under the same wind conditions, the angle of drift (the angle between the track direction and the leading line) increased with altitude, but the number of birds that compensated for drift decreased. On average, at heights below 300 m agl, the thrushes were capable of compensating completely for moderate winds; between 300 and 600 m agl compensation was partial; but above 600 m the birds drifted completely. Birds of the same species flying above the same terrain may demonstrate different reactions to the same crosswind depending on altitude. Meanwhile, flight tracks gradually deviated from the leading line with an increase in altitude, the headings of the birds got closer to the general migratory direction. It is more likely that the birds control displacement using the visual flow regulation principle by the angular velocity of the landmarks below them running aside in relation to their flight direction, which is inversely proportional to the altitude. Low flying thrushes promptly reacted to the shifting of the leading line of the spit with an average angular velocity of more than 0.8°/s perpendicular to the direction of flight and compensated completely for drift. Shifting of the leading line with an angular velocity of less than 0.4°/s, the high flying birds did not seem to notice or did not try to compensate for displacement deliberately.
... However, strong competitive interactions decrease the rate of species co-occurrence, so of local species richness, while shared habitat preferences and the lack of strong antagonistic interactions lead to positive co-occurrence patterns. In the past decades, habitat loss, climate change and other forms of human-caused mortality (Calvert et al., 2013;Loss, Will, & Marra, 2012) have contributed to the global loss in abundance of animal populations and changes in the number and magnitude of species associations (Rosenberg et al., 2019). ...
Aim
To evaluate the patterns of bird assemblage and distribution in an endangered grassland system, taking into accounts both environmental and biotic effects. To further focus on an endangered songbird and associated steppe birds.
Location
Inner Mongolia, China.
Methods
We investigated the relative importance of abiotic and biotic factors driving the abundance and co‐occurrence of steppe birds in Inner Mongolia by using joint species distribution models. We examined the general patterns of species assemblage, with a focus on the endangered Jankowski's Bunting and other species potentially sharing the same niche or interacting with it, including potential competitors (especially the closely related Meadow Bunting), predators (corvids, raptors) and a parasite (cuckoo).
Results
The studied steppe species exhibited varied responses to environmental variables, including climate, landscape and habitat predictors. We observed stronger species correlations due to residual covariates than to abiotic covariates. Jankowski's Bunting displayed strong positive co‐occurrences with other ground‐nesting songbirds and exhibited significant responses to all measured habitat and climate variables, indicating that this endangered bird has a high niche specialization and wide associations with other sympatric steppe bird species.
Main conclusion
Our results pointed out that climate, landscape and steppe habitat predictors are not the only factors structuring bird assemblages. Our results suggested that Jankowski's Bunting is an indicator of the occurrence of other species, especially open‐nesting specialized steppe songbirds, so it could act as a surrogate for overall steppe bird conservation. These findings are helpful for understanding how abiotic and biotic processes interactively alter bird communities and making effective management decisions to mitigate multiple threats to the entire community.
... In practical terms, this means that a site manager with counts of individuals killed can have difficulty interpreting the relevance of those data relative to reductions in the population growth rates. These difficulties inhibit assessments of the consequences to wildlife of many anthropogenic stressors (Loss et al. 2012(Loss et al. , 2015. Making this leap, from count-based field data to rate-based estimates describing the larger population (i.e., upscaling; May et al. 2019), therefore is critical to interpreting the relevance of models describing the consequence of anthropogenic stressors on wildlife populations. ...
Human activity influences wildlife. However, the ecological and conservation significances of these influences are difficult to predict and depend on their population-level consequences. This difficulty arises partly because of information gaps, and partly because the data on stressors are usually collected in a count-based manner (e.g., number of dead animals) that is difficult to translate into rate-based estimates important to infer population level consequences (e.g., changes in mortality or population growth rates). However, ongoing methodological developments can provide information to make this transition. Here, we synthesize tools from multiple fields of study to propose an overarching, spatially explicit framework to assess population-level consequences of anthro-pogenic stressors on terrestrial wildlife. A key component of this process is using ecological information from affected animals to upscale from count-based field data on individuals to rate-based demographic inference. The five steps to this framework are (1) framing the problem to identify species, populations, and assessment parameters ; (2) field-based measurement of the effect of the stressor on individuals; (3) characterizing the location and size of the populations of interest; (4) demographic modeling for those populations; and (5) assessing the significance of stressor-induced changes in demographic rates. The tools required for each of these steps are well developed, and some have been used in conjunction with each other, but the entire group has not previously been unified together as we do in this framework. We detail these steps and then illustrate their application for two species affected by different anthropogenic stressors. In our examples, we use stable hydrogen isotope data to infer a catchment area describing the geographic origins of affected individuals, as the basis to estimate population size for that area. These examples reveal unexpectedly greater potential risks from stressors for the more common and widely distributed species. This work illustrates key strengths of the framework but also important areas for subsequent theoretical and technical development to make it still more broadly applicable.
... Further, although characteristics of the outlier buildings appear to influence which collision correlates were identified and therefore provide insight into collision risk factors for these structures, greater replication of large, glassy, and irregularly shaped buildings (including stadiums) would more conclusively identify bird collision risk factors that are generalizable to multiple contexts. This increased replication could be achieved through coordinated and standardized collision monitoring in multiple cities (e.g., following [14]), meta-analyses of published and unpublished datasets, and creation of a bird collision database to facilitate data sharing among researchers, conservation organizations, and building designers (see also [53]). ...
Bird-building collisions are the largest source of avian collision mortality in North America. Despite a growing literature on bird-building collisions, little research has been conducted in downtown areas of major cities, and no studies have included stadiums, which can be extremely large, often have extensive glass surfaces and lighting, and therefore may cause many bird collisions. Further, few studies have assessed the role of nighttime lighting in increasing collisions, despite the often-cited importance of this factor, or considered collision correlates for different seasons and bird species. We conducted bird collision monitoring over four migration seasons at 21 buildings, including a large multi-use stadium, in downtown Minneapolis, Minnesota, USA. We used a rigorous survey methodology to quantify among-building variation in collisions and assess how building features (e.g., glass area, lighting, vegetation) influence total collision fatalities, fatalities for separate seasons and species, and numbers of species colliding. Four buildings, including the stadium, caused a high proportion of all collisions and drove positive effects of glass area and amount of surrounding vegetation on most collision variables. Excluding these buildings from analyses resulted in slightly different collision predictors, suggesting that factors leading some buildings to cause high numbers of collisions are not the exact same factors causing variation among more typical buildings. We also found variation in collision correlates between spring and fall migration and among bird species, that factors influencing collision fatalities also influence numbers of species colliding, and that the proportion, and potentially area, of glass lighted at night are associated with collisions. Thus, reducing bird collisions at large buildings, including stadiums, should be achievable by reducing glass area (or treating existing glass), reducing light emission at night, and prioritizing mitigation efforts for glass surfaces near vegetated areas and/or avoiding use of vegetation near glass.
... Moreover, these comparisons of total numbers of animals killed overlook that important impacts on certain wildlife species and populations can still occur even when overall mortality is relatively low. Our conclusions regarding inconsistencies in mortality indicators align with previous recommendations to standardize study design and data collection and reporting methods, both for energy impacts and anthropogenic wildlife mortality more broadly (Loss et al. 2012, Huso et al. 2016). This review further highlights that comparisons of direct mortality among energy sources also require increased standardization across multiple energy sources. ...
Comparing environmental impacts of different energy sources can inform energy investments and environmental conservation. Direct wildlife mortality from energy development receives substantial public and scientific attention, but it is unclear whether rigorous comparisons of mortality among energy sources are possible. To address this question, we compared availability of mortality studies among energy sources, wildlife groups, and regions, and assessed comparability of mortality indicators measured. Whereas wind and hydropower have received substantial mortality research exceeding their proportional contributions to global energy production, coal, oil and gas, and bioenergy have received fewer studies and are underrepresented relative to their contributions. Furthermore, research is biased toward birds and fish and North America and Europe, and there are inconsistencies among energy sources and limited replication of most indicators measured. These results indicate that rigorous comparisons of direct wildlife mortality among energy sources are not currently possible and highlight research needs for improving understanding of energy's environmental impacts.
... In 2012, Loss et al. (2012) published a paper in which they complained that "national mortality estimates are often based on extrapolation from a limited sample of small-scale studies, and estimates of uncertainty are ignored or only superficially assessed." One year later, the authors included some of these very studies in "The impact of free-ranging domestic cats." ...
... Anthropogenic sources of mortality represent a significant loss to many bird species across North America [1]. Direct sources of human-caused mortality range from window collisions PLOS to feral cats [2]. ...
Millions of birds in the United States die annually due to vehicle collisions on roads. Collisions may be of particular interest for species of conservation concern, such as the endangered Hawaiian goose (Nēnē), which is endemic to Hawai‘i. Using a nearly 40-year dataset of Nēnē road mortality in and around Hawai‘i Volcanoes National Park, we sought to answer the following research questions: 1) has Nēnē mortality changed over time? 2) are there times of the year in which mortality is greatest and does it relate to specific events in the species’ lifecycle? 3) does age at mortality differ over time, space, or sex? 4) given that existing mortalities appear to occur only in certain locations, do the number of mortality events differ across these locations; 5) does mortality rate show any density dependence? and, 6) are mortality rates related to numbers of visitors or vehicles? Between 1977 and 2014, a total of 92 Nēnē died from vehicle collisions; while absolute mortality increased over this time, the mortality rate remained the same. Similarly, average age of mortality increased over time, but did not differ by location or sex. Between 1995 and 2014, Nēnē population size and mortality rates were not correlated. Mortality was greatest in November and December (breeding season) and lowest in June. Most of the mortality occurred along just three stretches of road in and around the park, with the number of mortalities split about evenly inside and outside of the park. Furthermore, Nēnē mortality was unrelated to the number of visitors or traffic volume in the park. These findings suggest vehicle collisions are a growing concern for Nēnē, but that management actions to reduce mortality can be targeted at specific road segments and times of the year.
... Yet, the thorough evaluation of the magnitude of natural and anthropogenic mortality sources is insufficient within and across avian species (Loss et al. 2015; but see Thorup et al. 2013 for Little Owl). In order to advance our understanding about the impacts of anthropogenic mortality on avian populations and to inform conservation management, it is required to 1) assess the magnitude of all mortality sources, 2) obtain mortality data throughout the annual cycle, and 3) address variation in mortality rates using large-scale data across extensive geographic areas (Loss et al. 2012(Loss et al. , 2015. ...
Anthropogenic mortality has a considerable impact on populations of long-lived species, such as raptors, which increasingly inhabit human-dominated landscapes. Here, we analyzed long-term mortality data for two rapidly declining owls, Little Owl Athene noctua and Barn Owl Tyto alba, in the Czech Republic. We evaluated relative mortality rates with respect to owl age, month of carcass recovery, and two time periods (before and after year 2000). We examined 961 mortality records (199 Little Owls and 762 Barn Owls) derived from six distinct database sources totally spanning the period of years 1934–2017 and the entire Czech Republic. Natural causes, entrapment in vertical hollow objects and drowning in liquid reservoirs (entrapment), and collision with vehicles accounted for the highest proportion of mortality cases in Little Owl, while collision with vehicles and entrapment represented the most important mortality sources in Barn Owl. Relative mortality rates in Little Owl caused by entrapment, non-vehicle collision, electrocution at power lines and confinement in buildings increased after the year 2000. In turn, the relative mortality rate due to collision with vehicles increased after 2000 in Barn Owl. Persecution, collision with vehicles, and entrapment accounted for higher relative mortality rates in first-year than adult Little Owls. In Barn Owls, higher relative mortality rates due to collision with vehicles and entrapment were detected in adult compared to first-year birds. Finally, relative mortality rates differed between age classes according to the month of carcass recovery for both species. For Little Owl, the highest relative mortality rates in first-year individuals were detected during July and September, whereas adult Little Owls suffered the highest relative mortality rates during March, November and December. In Barn Owls, the relative mortality rates of first-year individuals peaked in November and December, whereas adult birds suffered the highest relative mortality rate during July, January and February. This study strongly suggests that reducing the risk of anthropogenic mortality may be crucial to halt the decline of Little Owl and Barn Owl populations.
... Lead poisoning is also about the health of individual animals. Loss et al. (2012) reviewed the topic of human-caused mortality and impact on populations, and commented that: ...
This review presents evidence of lead exposure and toxicity to wildlife and humans from spent shotgun and rifle ammunition and fishing weights, and the barriers and bridges to completing the transition to non-lead products. Despite the international availability of effective non-lead substitutes, and that more jurisdictions are adopting suitable policies and regulations, a broader transition to non-lead alternatives is prevented because resolution remains divided among disparate human user constituencies. Progress has occurred only where evidence is most compelling or where a responsible public authority with statutory powers has managed to change mindsets in the wider public interest. Arguments opposing lead bans are shown to lack validity. Differing national regulations impede progress, requiring analysis to achieve better regulation. Evidence that lead bans have reduced wildlife exposure should be used more to promote sustainable hunting and fishing. Evidence of the lead contribution from hunted game to human exposure should shape policy and regulation to end lead ammunition use. The Special Issue presents evidence that a transition to non-lead products is both warranted and feasible.
... Examples of studies employing BACI designs include white-tailed eagles (Dahl et al., 2012), golden plover (Pluvialis apricaria) (Sansom et al., 2016), grassland birds (Shaffer and Buhl, 2016), fish communities (Stenberg et al., 2015), and harbour porpoises (Scheidat et al., 2011). BACI approaches are in general recommended (Loss et al., 2012). Such a design requires monitoring population trends in the wind-power plant sites and a control site both pre-and postconstruction. ...
The expansion of wind energy poses challenges to policy-and decision-makers to address conflicts with wildlife. Conflicts are associated with impacts of existing and planned projects on wildlife, and associated difficulties of prediction where impacts are subject to considerable uncertainty. Many post-construction studies have demonstrated adverse effects on individuals of various bird and bat species. These effects may come in the form of collision-induced mortality or behavioral or physiological changes reducing the fitness of individuals exposed to wind energy facilities. Upscaling these individual effects to population impacts provides information on the true value of interest from a conservation point of view. This paper identifies methodological issues associated when moving from individual effects to population impacts in the context of wind energy. Distinct methodological approaches to predict population impacts are described using published case studies. The various choices of study design and metrics available to detect significant changes at the population level are further assessed based on these. Ways to derive impact thresholds relevant for decision-making are discussed in detail. Robust monitoring schemes and sophisticated modelling techniques may inevitably be unable to describe the whole complexity of wind and wildlife interactions and the natural variability of animal populations. Still, they will provide an improved understanding of the response of wildlife to wind energy and better-informed policies to support risk-based decision-making. Policies that support the use of adaptive management will promote assessments at the population level. Providing information to adequately balance the development of wind energy with the persistence of wildlife populations.
... Wolf also criticizes the broad uncertainty around the Loss et al. (2013) predation estimates, citing an earlier paper by the same authors (Loss et al. 2012) highlighting limitations of wildlife mortality estimates that are extrapolated from a limited sample of data and do not account for uncertainty. Thus, Wolf attempts to discredit Loss et al. (2013) by claiming their methods do not follow their own recommendations. ...
Misinformation (or denialism), the disingenuous assertion of information contradicting overwhelming scientific consensus, increasingly poses a challenge for invasion biology. The issue of free-ranging domestic cats (Felis catus) provides an example of this misinformation: overwhelming consensus shows that cats are invasive species that impact wildlife and human health yet free-ranging cat advocates propagate misinformation about such impacts to support policies keeping cats on the landscape. These advocates also attempt to discredit peer-reviewed scientific research on cat impacts, as exemplified by the response to a high-profile paper estimating cats
annually kill billions of U.S. birds and mammals (Loss et al. in Nat Commun 4:1396, 2013). Although favorably received by scientific and invasive species management communities, an effort was launched to
discredit this paper by criticizing its methods, including a report commissioned by a feral cat advocacy group and a post by a feral cat blogger. These same organizations and individuals have made similar
criticisms at scientific conferences and policy roundtables. Given the realized effects of this campaign in influencing invasive species policy, we here respond to these criticisms and show they are characterized by numerous errors and misrepresentations. We conclude that the criticisms are part of the broader campaign to fabricate doubt about outdoor cat impacts and stymie policies favoring removal of cats from the landscape. Because misinformation surrounding cats is emblematic of the broader issue of misinformation and denialism, this response will not only facilitate evidence-based policy for managing cats but also stimulate research and discussion into causes and
impacts of misinformation in invasion biology.
... Several studies suggest that power line collision mortality can have significant population-level impacts (Loss et al., 2012;Schaub et al., 2010;Schaub and Pradel, 2004), and red-listed and economically important species are commonly documented casualties (Bevanger, 1995a(Bevanger, , 1998Hobbs, 1987;Janss, 2000). In some cases, there is evidence that power line collision mortality can even lead to changes in migratory patterns and flyways (Palacín et al., 2017). ...
Transmission and distribution electricity grids are expanding rapidly worldwide, with significant negative impacts on biodiversity and, in particular, on birds. We performed a systematic review of the literature available on bird collisions with power lines to: (i) assess overall trends in scientific research in recent decades; (ii) review the existing knowledge of species-specific factors (e.g. vision, morphology), site-specific factors (e.g. topography, light and weather conditions, and anthropogenic disturbance), and power line-specific factors (e.g. number of wire levels, wire height and diameter) known to contribute to increased bird collision risk; and (iii) evaluate existing mitigation measures (e.g. power line routing, underground cabling, power line configuration, wire marking), as well as their effectiveness in reducing collision risk. Our literature review showed (i) there is comparatively little scientific evidence available for power line-specific factors, (ii) there is a scarcity of studies in Asia, Africa and South America, and (iii) several recommendations of good practice are still not supported by scientific evidence. Based on knowledge gaps identified through this review, we outline suggestions for future research and possible innovative approaches in three main areas: bird behaviour (e.g. further use of loggers and sensors), impact assessment (e.g. understanding the drivers of mortality hotspots, assess population-level impacts , develop methods for automatic detection of collisions) and mitigation measures (e.g. further need of BACI approaches to compare the effectiveness of different wire marking devices). The complex and region-specific interactions between collision drivers and bird ecology continue to limit our ability to predict impacts and the success of mitigation measures.
... Detecting the key factors involved in wildlife mortality due to wildlife-vehicle collision is a prerequisite for effective mitigation measures [75][76][77][78][79][80]. Roads, traffic, transmission towers, artificial lights and other infrastructure related to road network features have rapidly increased in the Canary Islands in the last four decades [34], and will probably continue increasing. ...
Insular wildlife is more prone to extinction than their mainland relatives. Thus, a basic understanding of non-natural mortality sources is the first step in the development of conservation management plans. The Canary Islands are an important tourist destination due to their unique climate and rich scenery and biodiversity. During the last few decades, there has been significant development of urban areas and busy road networks. However, there have been no studies describing the effects of road mortality on wildlife in this archipelago. We describe the temporal and spatial patterns of wildlife roadkill in Lanzarote (UNESCO Biosphere Reserve), using counts from cars for an entire annual cycle. A total of 666 roadkills were recorded (monthly average of 0.09 birds/km and 0.14 mammals/km) comprising at least 37 species including native birds and introduced mammals. Seasonal abundance, richness and diversity of roadkills showed a high peak during summer months for both mammals and birds. GLMs indicated that accidents (including birds and mammals) have a higher probability of occurrence close to houses and on roads with high speed limits. When analysed separately, mammal kills occurred in sectors with high speed limits, close to houses and in areas surrounded by exotic bushes, while bird roadkills appeared in road sectors with high speed limits, close to houses and low traffic volume. Our findings highlight that roads are a potential threat to native birds in the eastern Canary Islands. Detailed studies on the local population dynamics of highly affected species, such as the Houbara Bustard, Eurasian Stone Curlew, Barn Owl or Southern Shrike, are urgently needed to determine whether these levels of road mortality are sustainable.
... While natural threats are less subject to human control, sources of anthropogenic mortality can be challenging to manage (Loss et al. 2012). This is the case with mortality caused by overhead power lines, wind farms and buildings, or hunting and illegal killing (Erickson et al. 2005, Tourenq et al. 2005, Loss et al. 2014, Silva et al. 2014. ...
The Little Bustard Tetrax tetrax (Linnaeus, 1758) is a medium-sized, ‘Near Threatened’ steppe bird, whose Iberian population has been alarmingly declining over recent decades. Although this population loss has been mainly attributed to agricultural intensification, there is no information on Little Bustard adult mortality levels and their drivers. Based on a joint effort combining all the tracking data on adult Little Bustards collected over a period of 12 years by all research teams working with the species in Iberia, we found that annual anthropogenic mortality is likely to have a critical impact on the species, with values almost as high as the mortality attributed to predation. Collision with power lines was found to be the main anthropogenic threat to the adult population (3.4–3.8%/year), followed by illegal killing (2.4–3%/year), which had a higher impact than initially foreseen. Our work shows how poorly understood and previously unknown threats are affecting the survival of the most important Little Bustard population in Europe.
... Predation by introduced cats has been a major cause of extinction for many species, with such impact particularly pronounced for island-endemic vertebrates (Blackburn et al., 2004;Blackburn et al., 2005;Doherty et al., 2016;Medina et al., 2011;Nogales et al., 2013) and for mammals in Australia (Woinarski et al., 2015). In contrast, the impacts of predation by cats on continental bird faunas is less well resolved, although cats are known to kill hundreds of millions to billions of birds annually in continental settings (Blancher, 2013;Dauphiné and Cooper, 2009;Loss et al., 2013), with such predation shown to be a major source of bird mortality (Loss et al., 2012(Loss et al., , 2015. ...
... Although some bird species may be experiencing population declines due to this cause (Klem 1990;Loss et al. 2015), a recent meta-analysis has suggested no causal relationships between bird collisions and population declines (Arnold and Zink 2011). Regarding the role of cats on bird populations, studies have suggested that direct predation is a major driver of avian populations (Baker et al. 2008;van Heezik et al. 2010;Loss et al. 2012), as well as some indirect effects, such as cat presence at bird nest sites reducing subsequent parental provisioning rates to chicks (Bonnington et al. 2013), which can in turn decrease nestling growth rates and decrease reproductive success (Dunn et al. 2010;Martin et al. 2011). ...
We here provide a general overview of the study of bird abundance, demography, and populations in urban environments with special attention on those from Latin America. We found that studies focused on bird abundance and demography were more common in Argentina, Brazil, and Mexico. We classified those species taken into account in four or more studies according to their response to urbanization. In general, specialist birds are negatively related with urbanization, whereas two invasive exotics, the Rock Pigeon (Columba livia) and House Sparrow (Passer domesticus), are present in most of the reviewed urbanized areas along Latin America. Although scarce, studies of bird demography revealed, in general, higher bird survival in urban environments, possibly due to lower predator density. However, anthropogenic causes have been identified to affect bird populations in urban areas (e.g., window and vehicle collisions, nest predation, predation by domestic cats and dogs). Future studies will importantly add to our knowledge of urban bird ecology in Latin America by continuing to quantify bird numbers and assess demography patterns, as well as identifying the factors that mold them. Birds, as highly informative and charismatic bioindicators, could play a crucial role in adding evidence-based knowledge for decision-makers to take action in building bird-friendly and livable cities.
Flight observations and carcass searches were carried out along distribution power lines in Slovakia. 77 km of 22 kV and 110 kV lines were marked on a total of 108 sections to evaluate the effectiveness of three types of bird flight diverters (FireFly Bird Diverter, RIBE Bird Flight Diverter and SWAN-FLIGHT Diverter) designed to increase power line visibility. Numbers of carcasses were compared before and after installation of the devices and reaction distances on marked power lines were surveyed. We observed a 93.5% reduction (93 vs. 6) in the number of fatalities under the marked power lines after line marking (06/2016–06/2019) compared to the period before installation (12/2014–02/2016). 2,296 flight reactions were observed and an estimated total of 41,885 individuals (57 bird species belonging to 13 orders) were recorded with their reactions to marked lines in the period 06/2016–06/2019. After installation of bird diverters, there was a low proportion of flight distance observations at the closest distance, i.e. up to 5 m, indicating that birds reacted further away from marked lines. Although we lack flight observations for the period before the installation of diverters, the reactions of birds at greater distances and reduced number of bird victims under marked lines indicate that all tested diverters have a positive effect on reducing the number of avian collisions with power lines.
Bird-window collisions occur across North America and are estimated to kill hundreds of millions of birds annually. Previous studies show that collisions occur non-randomly and can be influenced by building characteristics, time-of-year, and species-specific physiology and behaviour. Much of the available research is based in northeastern North America, though different species and habitats in the West may be affected differently. We collected strike data from 2 buildings in Victoria, British Columbia, from June to October 2018. We found that window width was positively related to the probability of a strike occurring, whereas vegetation distance to window, window aspect, and the building at which it occurred did not predict strike probability. A substantial increase in strikes occurred in September and October, which coincides with peak migration on Vancouver Island, and suggests that migration influences collision risk to bird species.
Studies documenting bird mortality from collisions with glass on buildings estimate hundreds of millions of birds die each year in North America from this cause alone. To reduce this mortality, it is essential to provide an objective assessment of the relative collision threat posed by glass and other materials incorporating patterns intended to deter collisions, similar to ratings for insulation value and breaking strength, for use by building professionals such as architects, engineers, planners, and other decision makers. We wanted to determine whether we could use a non-injurious binomial choice test developed in Austria, with local bird taxa in Pennsylvania, to provide objective collision threat ratings. Preliminary work in 2010-11 tested three patterns tested in Austria in 2004-6 and produced virtually identical scores leading to the conclusion that the test should apply generally to passerines. Additional trials indicated that variables including dimensions of pattern elements, spacing and orientation may interact in producing tunnel scores. The tunnel test has the potential to: a) determine how size, orientation and spacing of pattern elements impact collision-reduction effectiveness, b) rate commercially available glass, and c) evaluate new bird-friendly technologies. Keywords: Glass collisions, Bird collisions, Anthropogenic bird mortality, Tunnel test, Glass testing, Bird strikes
The science of urban ecology has increasingly grappled with the long‐term ramifications of a globally urbanized planet and the impacts on biodiversity. Some researchers have suggested that places with high species diversity in cities simply reflect an extinction debt of populations that are doomed to extinction but have not yet disappeared. The longitudinal studies conducted to date have found species composition shifting with urbanization but have not always documented continued species extirpations post‐urbanization. We used long‐term monitoring data on birds from the greater metropolitan area of Phoenix, Arizona, to measure changes in residential bird communities, species–habitat relationships, and human perceptions of bird species diversity over a five‐year period. Bird richness, occupancy, and abundance decreased, as did the percentage of respondents satisfied with bird variety in their neighborhoods. As in previous analyses for this region, we found that desert specialist species were associated with neighborhoods with xeric landscaping consisting of gravel groundcover, and drought‐tolerant, desert‐adapted vegetation. These species were also found in neighborhoods with high per capita income rates and lower percentages of renters and Hispanic/Latinx residents. Non‐native species were positively associated with neighborhoods containing mesic yards with grass and other water‐intensive vegetation. The proportions of yards in our surveyed neighborhoods with these distinct landscaping types likewise remained relatively stable over five‐year period. Although habitat–species relationships remained unchanged, we detected significant loss of species across the sampling period. Declines were not confined to desert specialist species but included generalist and invader species as well. The parallel reduction in residents’ satisfaction suggests that people perceive some aspect of this environmental degradation. Further investigation into the mechanisms underlying these species losses may reveal options for retaining some desert specialist species, and the uniqueness they contribute to urban fauna.
The book chapter contains the following sections:
- Birds in human culture
- Birds in coupled-human-natural systems
- The social context of bird-oriented actions
- Ecosystem services and disservices
Download the figures here: https://jhupbooks.press.jhu.edu/title/ornithology
Anthropogenic alterations to landscape are indicators of potential compromise of that landscape’s ecology. We describe how alterations can be assessed as ‘hazards’ to wildlife through a sequence of three steps: diagnosing the means by which the hazard acts on individual organisms at risk; estimating the fitness cost of the hazard to those individuals and the rate at which that cost occurs; and translating that cost rate into a demographic cost by identifying the relevant demographically-closed population. We exploit the conservation-oriented literature on wind farms to illustrate this conceptual scheme. For wind farms, the third component has received less attention than the first two, which suggests it is the most challenging of the three components. A wind farm provides an example of a ‘spatially localized hazard’, i.e., a discrete alteration of landscape hazardous to some population but of which there are some individuals that do not interact directly with the hazard themselves but nevertheless suffer a reduction in fitness in terms of their contribution to the next generation. Spatially localized hazards are identified via the third component of the scheme and are of particular conservation concern as, by their nature, their depredations on wildlife may be underestimated without an appropriate population-level estimation of the demographic cost of the hazard.
Bird strikes were recorded at the windows of commercial and private buildings to study the effects of collision mortality on birds, and several experiments were conducted to evaluate methods of preventing collisions between birds and glass panes. Two single houses that were systematically monitored annually killed 33 and 26 birds, respectively. Collisions at one house in the same 4-mo period (September- December) in consecutive years resulted in 26 and 15 fatalities, respectively. At least one out of every two birds were killed striking the windows of these single dwellings. The records from these homes also revealed that window strikes are equally lethal for small and large species. The annual mortality resulting from window collisions in the United States is estimated at 97.6-975.6 million birds. Experimental evidence indicates that complete or partial covering of windows will eliminate bird strikes. If parts of the window are altered, objects or patterns placed on or near the window must be no more than 5-10 cm apart and uniformly cover the entire glass surface. Eliminating bird attractants from the vicinity of windows will reduce or prevent strikes by reducing the number of birds near the glass hazard. If removal of attractants is unacceptable, place them within 0.3 m of the glass surface; birds are drawn to the attractant on arrival and are not able to build up enough momentum to sustain serious injury if they hit upon departure. My experimental results further reveal that the common practice of placing single objects such as falcon silhouettes or owl decoys on or near windows does not significantly reduce bird strikes. Window casualties represent a potentially valuable, but largely neglected source of data capable of contributing information on species geographic distributions, migration patterns, and various other studies requiring specimens.
Migration is a diverse behavior found in all animal taxa, and in its simplest form, is defined as a repeated seasonal movement to and from a breeding area. Animals exhibit several forms of migration, including seasonal migrations across latitudes, altitudinal migrations up and down mountains,
migrations that overlap with key life-history stages such as molt, and migrations that can span multiple generations over space and time.This variation can occur within species or between species, but all forms of migration involve movement away from breeding areas and then a return.
The geographic linking of individuals or populations between different stages of the annual cycle, including
between breeding, migration, and winter stages, is known as migratory connectivity. In this article, we will discuss why understanding migratory connectivity is so critical from ecological, evolutionary, and conservation perspectives and also provide descriptions of the various approaches
being used to track animals throughout the annual cycle. Most of our examples will be drawn from the bird literature because this is where the understanding is most advanced.
Understanding the connectivity between breeding and nonbreeding populations of migratory birds is fundamental to our knowledge of biological phenomena such as population dynamics and dispersal. Moreover, our ability to quantify migratory connectivity has inevitable consequences for both conservation and management of species that utilize distinct geographic locations. Technology is rapidly advancing our ability to track birds throughout the annual cycle and to collect data on the degree of connectivity among breeding and nonbreeding populations. We combined two direct methods, mark recapture (n = 17) and geolocation (n = 6), to estimate the migratory connectivity of breeding and nonbreeding populations of Gray Catbirds (Dumetella carolinensis). Data from geolocators show that birds breeding in the Mid-Atlantic overwinter in both Cuba and southern Florida. Mark recapture data supported our geolocator results but also provided a broader spatial perspective by documenting that Mid-Atlantic and Midwestern populations occupy distinct geographic localities during the nonbreeding period. This research underscores the importance of geolocators, as well as other tools, to advance our understanding of migratory connectivity. Finally, our results highlight the potential value of U.S. Geological Survey (USGS) Bird Banding Laboratory mark recapture data, which are often underutilized in ornithological research. Received 6 January 2011, accepted 24 April 2011.
Seabirds such as albatrosses and petrels are frequently caught in longline and trawl fisheries, but limited demographic data for many species creates management challenges. A method for estimating the potential biological removal (the PBR method) for birds requires knowledge of adult survival, age at first breeding, a conservation goal, and the lower limit of a 60% confidence interval for the population size. For seabirds, usually only the number of breeding pairs is known, rather than the actual population size. This requires estimating the population size from the number of breeding pairs when important demographic variables, such as breeding success, juvenile survival, and the proportion of the adult population that engages in breeding, are unknown. In order to do this, a simple population model was built where some demographic parameters were known while others were constrained by considering plausible asymptotic estimates of the growth rate. While the median posterior population estimates are sensitive to the assumed population growth rate, the 20th percentile estimates are not. This allows the calculation of a modified PBR value that is based on the number of breeding pairs instead of the population size. For threatened albatross species, this suggests that human-caused mortalities should not exceed 1.5% of the number of breeding pairs, while for threatened petrel species, mortalities should be kept below 1.2% of the number of breeding pairs. The method is applied to 22 species and sub-species of albatrosses and petrels in New Zealand that are of management concern, of which at least 10 have suffered mortalities near or above these levels.
Avian collision fatality data from studies conducted at 30 wind farms across North America were examined to estimate how many night migrants collide with turbines and towers, and how aviation obstruction lighting relates to collision fatalities. Fatality rates, adjusted for scavenging and searcher efficiency, of night migrants at turbines 54 to 125 m in height ranged from <1 bird/turbine/year to 7 birds/turbine/year with higher rates recorded in eastern North America and lowest rates in the west. Multi-bird fatality events (defined as >3 birds killed in 1 night at 1 turbine) were rare, recorded at <0.02% (n = 4) of 25,000 turbine searches. Lighting and weather conditions may have been causative factors in the four documented multi-bird fatality events, but flashing red lights (L-864, recommended by the Federal Aviation Administration [FAA]) were not involved, which is the most common obstruction lighting used at wind farms. A Wilcoxon signed-rank analysis of unadjusted fatality rates revealed no significant differences between fatality rates at turbines with FAA lights as opposed to turbines without lighting at the same wind farm.
We investigated how individual strategies combine with demographic and ecological factors to determine local and migratory move-ments in the double-crested cormorants (Phalacrocorax auritus). One hundred and forty-five cormorants were captured from 14 nesting colonies across the Great Lakes area and fitted with satellite transmitters. We first tested the hypotheses that sexual segrega-tion, density-dependent effects, and the intensity of management operations influenced home range size during the breeding season. The influence of these factors appeared to be limited in part due to random variability in foraging and dispersal decisions at individual and colony levels. We also designed a statistical framework to investigate the degree and determinants of migratory connectivity. Our analyses revealed a significant migratory connectivity in cormorants, although we also observed a nonnegligible amount of individual variability and flexibility. Our data were most consistent with the existence of a migratory divide across the Great Lakes, with western populations using mainly the Mississippi Flyway and eastern populations the Atlantic Flyway. Previous and current studies suggest that the divide cannot be explained by past divergence in isolation, a way to diminish travel cost, or the Appalachians constituting an ecological barrier per se but is rather the consequence of the distribution of suitable stopover and nonbreeding areas. However, a parallel migration system and no migratory divide could not be entirely ruled out with present data.
Bird mortality as a result of collisions with power lines has been of increasing concern in recent decades, but the real impact on bird populations requires an experimental assessment of scavenger removal rates and searcher detection errors. Farmland and steppe birds, two of the most threatened avian groups, have been shown to be particularly vulnerable to collision with power lines, but few removal and detectability studies have been developed in cereal farmland habitats, and none in the Mediterranean region. We conducted five carcass disappearance trials in central Spain by placing 522 corpses of different sizes under power lines, and searching for remains four times during the following month. The influence of several factors was examined using multivariate approach. The accumulated number of carcasses removed by scavengers increased logarithmically, with 32% removed over the 2-day period after the initial placement, but only 1.5% removed on a daily basis by day 28. Small birds disappeared earlier and at a higher proportion than larger birds. Carcass removal rates were site-dependent, but were not influenced by carcass density or season. The detection rate increased with the observer's previous experience and carcass size. Carcass counts at power lines notably underestimate bird casualties. Our 4-week disappearance equations provide a full range of scavenging rates and observer efficiency correction factors for a wide range of bird weights. Fortnightly to monthly search frequencies may be adequate to detect medium- to large-sized corpses, but are insufficient for smaller birds. Finally, all personnel participating in carcass searches should be trained previously in this task.
Two of the most significant management efforts affecting waterfowl populations in North America are the North American Waterfowl Management Plan (the Plan) and Federal harvest management programs. Both the Plan and harvest management are continental in scope, involve an extensive group of stakeholders, and rely on adaptive processes of biological planning, implementation, and evaluation. The development of these programs has occurred independently, however, and there has been little explicit recognition that both harvest and habitat effects should be considered for coherent management planning and evaluation. For example, the harvest strategy can affect whether population objectives of the Plan are met, irrespective of the success of the Plan's habitat conservation efforts. Conversely, habitat conservation activities under the Plan can influence harvest potential and, therefore, the amount of hunting opportunity provided. It seems increasingly clear that the Plan's waterfowl population objectives can only be useful for conservation planning and evaluation if they are accompanied by an explicit specification of the harvest strategy and environmental conditions under which they are to be achieved. This clarification also is necessary to ensure that Plan population objectives are not attained solely through the reduction of hunting opportunity. We believe then that it is imperative that these key waterfowl-management programs work to harmonize their objectives. Harvest management programs and the Plan ought to be working toward the same ends, but that is not possible so long as the mutually reinforcing relationship of these programs is obscured by ambiguities in their management objectives.
Following estimation of effects from a linear mixed model, it is often useful to form predicted values for certain factor/variate combinations. The process has been well defined for linear models, but the introduction of random effects into the model means that a decision has to be made about the inclusion or exclusion of random model terms from the predictions. This paper discusses the interpretation of predictions formed including or excluding random terms. Four datasets are used to illustrate circumstances where different prediction strategies may be appropriate: in an orthogonal design, an unbalanced nested structure, a model with cubic smoothing spline terms and for kriging after spatial analysis. The examples also show the need for different weighting schemes that recognize nesting and aliasing during prediction, and the necessity of being able to detect inestimable predictions.
We estimate that from 500 million to possibly over 1 billion birds are killed annually in the United States due to anthropogenic sources including collisions with human-made structures such as vehicles, buildings and windows, power lines, communication towers, and wind turbines; electrocutions; oil spills and other con-taminants; pesticides; cat predation; and commercial fishing by-catch. Many of the deaths from these sour-ces would be considered unlawful take under federal laws such as the Endangered Species Act, Migratory Bird Treaty Act, and the Bald and Golden Eagle Pro-tection Act. In this paper, we summarize this literature and provide the basis for the mortality projections for many of the apparent significant sources. Most of the mortality projections are based on small sample sizes, and on studies typically lacking adjustments for scav-enging and searcher efficiency biases. Although the estimates for each source often range by an order of magnitude, the cumulative mortality from all these sources continues to be a concern.
Conservation biology must be able to provide guidelines even when available data are incomplete, because data on rare and endangered species are usually limited. For instance, data on the effect of additional - human-induced - sources of mortality on vertebrate populations, such as bycatch of seabirds by longline fisheries, are typically incomplete. The importance of an additional source of mortality can be evaluated by comparing it with the maximum annual growth rate of the species of concern, and various authors have attempted to determine the maximum growth rate from incomplete data. We developed a procedure we call the "demographic invariant method" (DIM). First we determined that the maximum growth rate per generation does not vary, by recalling that it is a dimensionless number primarily independent of body weight and also by empirically establishing its near constancy over a restricted set of bird species for which reliable demographic information was available. This first step provided an implicit function linking generation time and maximum annual growth rate, from which we obtained the maximum annual growth rate as a simple function of generation time. From several different ways of obtaining estimates of generation time, we derived in turn several ways to estimate the maximum annual growth rate of a bird species from incomplete demographic data set. We applied our approach to the Black-footed Albatross (Phoebastria nigripes) and determined from incomplete data that longline fishery bycatch has a biologically significant impact on the growth potential of Black-footed Albatross populations. Our method can be applied broadly to the conservation and management of harvested bird populations.
Avian mortality at communication towers in the continental United States and Canada is an issue of pressing conservation concern. Previous estimates of this mortality have been based on limited data and have not included Canada. We compiled a database of communication towers in the continental United States and Canada and estimated avian mortality by tower with a regression relating avian mortality to tower height. This equation was derived from 38 tower studies for which mortality data were available and corrected for sampling effort, search efficiency, and scavenging where appropriate. Although most studies document mortality at guyed towers with steady-burning lights, we accounted for lower mortality at towers without guy wires or steady-burning lights by adjusting estimates based on published studies. The resulting estimate of mortality at towers is 6.8 million birds per year in the United States and Canada. Bootstrapped subsampling indicated that the regression was robust to the choice of studies included and a comparison of multiple regression models showed that incorporating sampling, scavenging, and search efficiency adjustments improved model fit. Estimating total avian mortality is only a first step in developing an assessment of the biological significance of mortality at communication towers for individual species or groups of species. Nevertheless, our estimate can be used to evaluate this source of mortality, develop subsequent per-species mortality estimates, and motivate policy action.
Evidence suggests that nest predation is a serious problem for the conservation of bird populations. Managers are, therefore, faced with decisions of whether to intervene to reduce this impact and if so what interventions to use. Nest predator exclusion is one of the most widely used methods for reducing predation, particularly for ground-nesting species, but studies testing its effectiveness have shown mixed results. We used explicit systematic review methodology to determine the impact of nest predator exclusion on hatching success. We used meta-analysis to summarise results from 16 predator exclusion studies. We also investigated whether factors relating to characteristics of the prey, predator species, location and study methodology explained heterogeneity in effect sizes. Predator exclusion using either exclusion fences or nest-cages resulted in a significant increase in hatching success. This was the case for declining as well as increasing bird populations indicating that nest predator exclusion is an effective method of increasing hatching success of vulnerable species. Nest-cages had a larger effect on hatching success than exclusion fences, although this difference was not significant and additional nest-cage studies are required as sample sizes were small. Heterogeneity in effect sizes was not explained by any of the covariates investigated. Studies have shown that nest-cages can lead to increased levels of predation on incubating adults and so should be used with caution especially within small populations. Research is required to determine whether increased hatching success following nest predator exclusion results in increased breeding populations as improving hatching success alone does not ensure improved conservation status of bird populations.
Road mortality is probably the best-known and visible impact of roads upon wildlife. Although several factors influence road-kill counts, carcass persistence time is considered the most important determinant underlying underestimates of road mortality. The present study aims to describe and model carcass persistence variability on the road for different taxonomic groups under different environmental conditions throughout the year; and also to assess the effect of sampling frequency on the relative variation in road-kill estimates registered within a survey.
Daily surveys of road-killed vertebrates were conducted over one year along four road sections with different traffic volumes. Survival analysis was then used to i) describe carcass persistence timings for overall and for specific animal groups; ii) assess optimal sampling designs according to research objectives; and iii) model the influence of road, animal and weather factors on carcass persistence probabilities. Most animal carcasses persisted on the road for the first day only, with some groups disappearing at very high rates. The advisable periodicity of road monitoring that minimizes bias in road mortality estimates is daily monitoring for bats (in the morning) and lizards (in the afternoon), daily monitoring for toads, small birds, small mammals, snakes, salamanders, and lagomorphs; 1 day-interval (alternate days) for large birds, birds of prey, hedgehogs, and freshwater turtles; and 2 day-interval for carnivores. Multiple factors influenced the persistence probabilities of vertebrate carcasses on the road. Overall, the persistence was much lower for small animals, on roads with lower traffic volumes, for carcasses located on road lanes, and during humid conditions and high temperatures during the wet season and dry seasons, respectively.
The guidance given here on monitoring frequencies is particularly relevant to provide conservation and transportation agencies with accurate numbers of road-kills, realistic mitigation measures, and detailed designs for road monitoring programs.
Avian biodiversity is threatened by numerous anthropogenic factors and migratory species are especially at risk. Migrating birds frequently collide with manmade structures and such losses are believed to represent the majority of anthropogenic mortality for North American birds. However, estimates of total collision mortality range across several orders of magnitude and effects on population dynamics remain unknown. Herein, we develop a novel method to assess relative vulnerability to anthropogenic threats, which we demonstrate using 243,103 collision records from 188 species of eastern North American landbirds. After correcting mortality estimates for variation attributable to population size and geographic overlap with potential collision structures, we found that per capita vulnerability to collision with buildings and towers varied over more than four orders of magnitude among species. Species that migrate long distances or at night were much more likely to be killed by collisions than year-round residents or diurnal migrants. However, there was no correlation between relative collision mortality and long-term population trends for these same species. Thus, although millions of North American birds are killed annually by collisions with manmade structures, this source of mortality has no discernible effect on populations.
Legal removal of migratory birds from the wild occurs for several reasons, including subsistence, sport harvest, damage control, and the pet trade. We argue that harvest theory provides the basis for assessing the impact of authorized take, advance a simplified rendering of harvest theory known as potential biological removal as a useful starting point for assessing take, and demonstrate this approach with a case study of depredation control of black vultures (Coragyps atratus) in Virginia, USA. Based on data from the North American Breeding Bird Survey and other sources, we estimated that the black vulture population in Virginia was 91,190 (95% credible interval = 44,520-212,100) in 2006. Using a simple population model and available estimates of life-history parameters, we estimated the intrinsic rate of growth (rmax) to be in the range 7-14%, with 10.6% a plausible point estimate. For a take program to seek an equilibrium population size on the conservative side of the yield curve, the rate of take needs to be less than that which achieves a maximum sustained yield (0.5 x rmax). Based on the point estimate for rmax and using the lower 60% credible interval for population size to account for uncertainty, these conditions would be met if the take of black vultures in Virginia in 2006 was <3,533 birds. Based on regular monitoring data, allowable harvest should be adjusted annually to reflect changes in population size. To initiate discussion about how this assessment framework could be related to the laws and regulations that govern authorization of such take, we suggest that the Migratory Bird Treaty Act requires only that take of native migratory birds be sustainable in the long-term, that is, sustained harvest rate should be <rmax. Further, the ratio of desired harvest rate to 0.5 x rmax may be a useful metric for ascertaining the applicability of specific requirements of the National Environmental Protection Act.
Emerging infectious diseases present a formidable challenge to the conservation of native species in the twenty-first century. Diseases caused by introduced pathogens have had large impacts on species abundances, including the American chestnut, Hawaiian bird species and many amphibians. Changes in host population sizes can lead to marked shifts in community composition and ecosystem functioning. However, identifying the impacts of an introduced disease and distinguishing it from other forces that influence population dynamics (for example, climate) is challenging and requires abundance data that extend before and after the introduction. Here we use 26 yr of Breeding Bird Survey (BBS) data to determine the impact of West Nile virus (WNV) on 20 potential avian hosts across North America. We demonstrate significant changes in population trajectories for seven species from four families that concur with a priori predictions and the spatio-temporal intensity of pathogen transmission. The American crow population declined by up to 45% since WNV arrival, and only two of the seven species with documented impact recovered to pre-WNV levels by 2005. Our findings demonstrate the potential impacts of an invasive species on a diverse faunal assemblage across broad geographical scales, and underscore the complexity of subsequent community response.
Two of the most significant management efforts affecting waterfowl populations in North America are the North American Waterfowl Management Plan (the Plan) and Federal harvest management programs. Both the Plan and harvest management are continental in scope, involve an extensive group of stakeholders, and rely on adaptive processes of biological planning, implementation, and evaluation. The development of these programs has occurred independently, however, and there has been little explicit recognition that both harvest and habitat effects should be considered for coherent management planning and evaluation. For example, the harvest strategy can affect whether population objectives of the Plan are met, irrespective of the success of the Plan's habitat conservation efforts. Conversely, habitat conservation activities under the Plan can influence harvest potential and, therefore, the amount of hunting opportunity provided. It seems increasingly clear that the Plan's waterfowl population objectives can only be useful for conservation planning and evaluation if they are accompanied by an explicit specification of the harvest strategy and environmental conditions under which they are to be achieved. This clarification also is necessary to ensure that Plan population objectives are not attained solely through the reduction of hunting opportunity. We believe then that it is imperative that these key waterfowl-management programs work to harmonize their objectives. Harvest management programs and the Plan ought to be working toward the same ends, but that is not possible so long as the mutually reinforcing relationship of these programs is obscured by ambiguities in their management objectives.
Migratory birds suffer considerable human-caused mortality from structures built to provide public serv- ices and amenities. Three such entities are increasing nationwide: communication towers, power lines, and wind turbines. Communication towers have been grow- ing at an exponential rate over at least the past 6 years. The U.S. Fish and Wildlife Service is especially con- cerned about growing impacts to some 836 species of migratory birds currently protected under the Migra- tory Bird Treaty Act of 1918, as amended. While mor- tality estimates are often sketchy, and won't be verified until nationwide cumulative impact studies are con- ducted, current figures are troubling. Communication towers may kill from 4-50 million birds per year. Col- lisions with power transmission and distribution lines may kill anywhere from hundreds of thousands to 175 million birds annually, and power lines electrocute tens to hundreds of thousands more birds annually, but these utilities are poorly monitored for both strikes and electrocutions. More than 15,000 wind turbines may kill 40,000 or more birds annually nationwide, the ma- jority in California. This paper will address the com- monalities of bird impacts among these industries; those bird species that tend to be most affected; and research (completed, current, and proposed) intended to reduce bird collisions and electrocutions nationwide. The issues of structure location (siting), lighting, guy supports, lattice or tubular structures, bird behavior, and habitat modifications are reviewed. In addition, this paper reviews the respective roles and publications of the Avian Power Line Interaction Committee and the Wildlife Workgroup of the National Wind Coordin- ating Committee, the roles of the Service-chaired Com- munication Tower Working Group and Wind Turbine Siting Working Group, and the Fish and Wildlife Ser- vices' voluntary tower and turbine siting and placement guidelines. An update on recent Communication Tower Working Group research initiatives will also be discus- sed along with promising research findings and needs.
Abstract MOdern man,serves as both a direct and an indirect cau~e,of the death of birds. In the early 1970's, human activity was responsible for the death of approximately 196 million birds per year, or about 1.9% of the wild birds of the continental United States that died each·year.,. Hunting was the largest direct mortality factor and accounted for about 61 % of human,related bird deaths. Control or prevention of avian depredations took about 1% of tl).e total, 'and all re search and propagation about 0.5%. Collision with man~made,objects was the greatest indirect human,cause of avian deaths. accounting for about 32% of the human,related deaths. Pollution and poisoning caused the death of about 2% of the total. A relatively few speci~s,account for most of this mortality but continue to maintain large, harvestable populations, suggesting that the numbers of most bird species are essetitiaUy unaf fected by the human,activities discussed. Other activities of man,t.hat do not necessarily result in the death of birds but rather 'reduce reproductive potential are more likely to have long-term effects on avian populations.,\ The causes of avian mortality are numerous. Such
While subsidised populations of feral cats are known to impact their prey populations, little is known about the ecological impact of inside/outside hunting cats (IOHC). We studied IOHC around a suburban nature preserve. Mail surveys indicated an average of 0.275 IOHC/house, leading to a regional density estimate of 0.32 IOHC/ha. A geographical model of cat density was created based on local house density and distance from forest/neighbourhood edge. IOHC hunted mostly small mammals, averaging 1.67 prey brought home/cat/month and a kill rate of 13%. Predation rates based on kills brought home was lower than the estimate from observing hunting cats (5.54 kills/cat/month). IOHC spent most outside time in their or their immediate neighbours' garden/yard, or in the nearby forest edge; 80% of observed hunts occurred in a garden/yard or in the first 10 m of forest. Radio-tracked IOHC averaged 0.24 ha in home-range size (95% minimum convex polygon (MCP)) and rarely entered forest. Confirming this, scent stations detected cats more often near the edge and more cats were detected in smaller forest fragments. There was no relationship between the number of cats detected in an area and the local small mammal abundance or rodent seed predation rates. Cold weather and healthy cat predator populations are speculated to minimise the ecological impact of IOHC on this area.