Conservation of predators and scavengers should take advantage of the application of interdisciplinary approaches that connect both ecosystem processes/services and con icts/disservices. Despite this, there is an overall lack of interdisciplinary research on ecosystem processes/services and con icts/disservices provided by aerial predators and scavengers like raptors. Our speci c goals here are: i) to assess the experts' viewpoints on ecosystem processes/services and con icts/disservices provided by raptors to people and ii) to know the main intervention strategies that experts consider effective for managing raptor populations. Through an online survey we obtained 87 surveys for four raptor groups: hawks and eagles (40%), vultures (29%), owls (16%), and falcons (15%). Experts agreed that many ecosystem processes/services and only a few con icts/disservices are provided by raptors to society. Experts indicated that four ecosystem processes/services were provided by all raptor groups (i.e., vultures, falcons, hawks and eagles, and owls), and another one was provided by all the predator groups (i.e., all but vultures). In contrast, no con ict/disservice was considered to be produced by all groups of raptors. According to experts, hawks and eagles were involved in only three con icts/disservices, vultures and owls in one, and falcons in none. Experts agreed that ve strategies are effective for raptor management. Raptor conservation experts' viewpoints were mismatched with evidence from raptor literature and, as we expected, this mismatch was higher when considering con icts/disservices produced than ecosystem processes/services provided by raptors to people. To successfully promote policies and practices for raptors conservation, experts need to base their viewpoints on raptor literature.
We examined long-term demography of an endangered subspecies, the Northern Aplomado Falcon (Falco femoralis septentrionalis), in South Texas, USA. The population has been managed and monitored since reintroductions began in 1993. Data spanning 1993–2018 enabled us to build an integrated population model (IPM) and a Cormack-Jolly-Seber model to estimate survival for three life stages (first-year, non-breeders, and breeders) and both sexes, abundance of males, fecundity, immigration, and emigration. Male falcons survived at lower rates than females during their first year; Hurricane Harvey caused a decline in survival rates of first-years and breeders; and fecundity increased after 2011 coinciding with changes in management focused on improving nest platforms and habitat quality. Both immigration of non-breeders and emigration were likely negligible for this population suggesting a potentially isolated population. The IPM likely overestimated immigration of breeders warranting further research. Population growth rates were greatest during years having more released captive-reared young and greater probabilities of breeder survival. Importantly, an apparent decrease in breeder survival of unknown cause occurred during 2006 to 2009 when breeder survival declined and remained low for several years. Our ability to identify the cause for reduced survival is now greatly hampered by the extended time that has passed, limiting the usefulness of our recent awareness of reduced survival for informing management and further highlighting the importance of real-time monitoring for proactive decision making processes. Our study greatly improves knowledge of demographics for a reintroduced, isolated, and intensively managed population of Aplomado Falcons. Applying this IPM to new data each year will enable adaptive management of the South Texas population by providing annual evaluations of vital rates along with revised assessments of monitoring and management.
Climate change is expected to have a profound impact on species distributions, contracting suitable climate space. Biodiversity areas are important to mitigate these negative effects but are static by design and thus do not account for future projections of species distributions. The Harpy Eagle Harpia harpyja has a broad range across lowland Neotropical forests and thus its distribution could be negatively affected by climate change when combined with current rates of habitat loss. To test this hypothesis, we use spatial point process models fitted with climatic, topographic, and landcover covariates to identify current distribution. We then project to 24 future climate scenarios, using three General Circulation Models (GCMs), and two emission scenarios between the years 2021 and 2100 averaged over four 20-year periods. Our current model identified a core range across Amazonia and the Guiana Shield, with evergreen forest (71 %), mean diurnal temperature range (13 %), and elevation (6 %) the most important predictors. Reclassifying the current model to a binary prediction estimated a range size of ~7.6 million km², with the Important Bird and Biodiversity Area (IBA) network covering 18 % of habitat (~1.4 million km²) within this range. By 2090, range size was predicted to decrease on average by 14.4 % under a higher emissions scenario, and 7.3 % under a lower emissions scenario. The IBA network would cover 14 % less area under a higher emissions scenario, and 3.3 % less distribution area under a lower emissions scenario by 2090. Southern Amazonia is predicted to have the greatest reduction in range size and subsequently highest loss of Harpy Eagle habitat within the IBA network. Our work demonstrates that the combination of climate change and subsequent habitat loss may result in substantial losses in distribution for this raptor across the southern edge of its range.
Large raptors are the most mobile top predators in fragmented landscapes and, consequently, they are key components of ecosystems. However, large raptors (e.g. eagles), requiring large areas of forested habitat, are also among the most threatened groups of raptors in the world and are directly and indirectly affected by habitat loss and fragmentation. The Black-and-chestnut Eagle (Spizaetus isidori) is a forest dependent species with a long period of natal dispersal. Here, we aim to assess home range size, mortality, and habitat selection of juvenile Black-and-chestnut Eagles during their natal dispersal in three populations within fragmented landscapes of the Tropical and Subtropical Andean Montane Forests of South America. During the first year of natal dispersal, juveniles occupied large home ranges (mean = 996.3 km2; SD± 606; range = 294-2130 km2). While juvenile eagles made their natal dispersal through fragmented landscapes, they consistently selected areas with higher remaining forest cover, medium elevations, and higher slopes than the mean available in the landscape. Our study showed that juvenile eagles can tolerate a certain level of fragmentation during the natal dispersal period, although they also face high mortality during this same period. Four of the six (67%) tagged juvenile eagles died during the study period. The high mobility of juvenile eagles may keep key ecosystem functions within fragmented landscapes of South America. In order to maintain viable populations of this top predator, it is urgent to mitigate non-natural mortality, mainly from direct human persecution, in fragmented landscapes.
Operators of wind power facilities can mitigate wildlife mortality by slowing or stopping wind turbines (hereafter “curtail”) when birds are at increased risk of collision. Some facility operators curtail when individual birds have flight characteristics (e.g. altitude, distance, or relative bearing of a bird’s flight path) that exceed some threshold value, but thresholds currently in use have not been empirically evaluated. Overly restrictive thresholds can cause turbine curtailment for birds that never enter rotor‐swept zones, thereby resulting in excess power loss. We evaluated the probability that birds, specifically eagles, entered the rotor‐swept zone (hereafter “entry probability”) in response to their flight characteristics. We used an automated monitoring system to classify individuals as eagles or non‐eagles and record flight paths of purported eagles at a wind facility in Wyoming, USA. We used logistic regression with occupancy dynamics and a distance‐dependent colonization process to model entry probability. This model thus allowed entry probability to decrease with horizontal distance to the nearest turbine. Probability of entry varied with distance to the nearest turbine and approached zero when that distance was > 202 m. Entry probability peaked when eagles flew 89 m above ground, corresponding to hub heights of turbines (80 m), and decreased to near‐zero at altitudes ≥ 200 m. Entry probabilities were greatest when flight paths were near the rotor‐swept zone and when eagles flew slowly toward the nearest turbine. Compass bearing of a flight path was not associated with entry probability. Our model accurately forecasted entry probability in Wyoming (AUC = 0.96) and was transferable to another facility in California, USA (AUC = 0.97); therefore our results may be applicable across a variety of settings. Curtailment criteria can be based on flight path characteristics to forecast entry into rotor‐swept zones. The use of distance and altitude thresholds when making curtailment decisions is justified. However, this analysis suggests alteration of the time to collision threshold, with curtailment initiated at greater distances as the speed of the bird decreases. Our novel modeling method and our results can inform curtailment criteria in any situation where curtailment decisions are made in real‐time.
Quantifying habitat use is important for understanding how animals meet their requirements for survival and provides information for conservation planning. Currently, assessments of range-wide habitat use that delimit species distributions are incomplete for many taxa. The Harpy Eagle (Harpia harpyja) is a raptor of conservation concern, widely distributed across Neotropical lowland forests, that currently faces threats from habitat loss and fragmentation. Here, we use penalized logistic regression to identify species-habitat associations and predict habitat suitability based on a new International Union for the Conservation of Nature range metric, termed Area of Habitat. From the species-habitat model, we performed a gap analysis to identify areas of high habitat suitability in regions with limited coverage in the key biodiversity area (KBA) network. Range-wide habitat use indicated that Harpy Eagles prefer areas of 70–75% evergreen forest cover, low elevation, and high vegetation species richness. Conversely, Harpy Eagles avoid areas of >10% cultivated landcover and mosaic forest, and topographically complex areas. Our species-habitat model identified a large continuous area of potential habitat across the pan-Amazonia region, and a habitat corridor from the Chocó-Darién ecoregion of Colombia running north along the Caribbean coast of Central America. Little habitat was predicted across the Atlantic Forest biome, which is now severely degraded. The current KBA network covered 18% of medium to high Harpy Eagle habitat exceeding a target biodiversity area representation of 10%, based on species range size. Four major areas of high suitability habitat lacking coverage in the KBA network were identified in north and west Colombia, western Guyana, and north-west Brazil. We recommend these multiple gaps of habitat as new KBAs for strengthening the current KBA network. Modelled area of habitat estimates as described here are a useful tool for large-scale conservation planning and can be readily applied to many taxa.
Traffic noise is one of the leading causes of reductions in animal abundances near roads. Acoustic masking of conspecific signals and adventitious cues is one mechanism that likely causes animals to abandon loud areas. However, masking effects can be difficult to document in situ and the effects of infrequent noise events may be impractical to study. Here, we present the Soundscapes model, a stochastic individual-based model that dynamically models the listening areas of animals searching for acoustic resources (“searchers"). The model also studies the masking effects of noise for human detections of the searchers. The model is set in a landscape adjacent to a road. Noise produced by vehicles traveling on that road is represented by calibrated spectra that vary with speed. Noise propagation is implemented using ISO-9613 procedures. We present demonstration simulations that quantify declines in searcher efficiency and human detection of searchers at relatively low traffic volumes, fewer than 50 vehicles per hour. Traffic noise is pervasive, and the Soundscapes model offers an extensible tool to study the effects of noise on bioacoustics monitoring, point-count surveys, the restorative value of natural soundscapes, and auditory performance in an ecological context.
The COVID-19 pandemic has underscored the need to strengthen national surveillance systems to protect a globally connected world. In low-income and middle-income countries, zoonotic disease surveillance has advanced considerably in the past two decades. However, surveillance efforts often prioritise urban and adjacent rural communities. Communities in remote rural areas have had far less support despite having routine exposure to zoonotic diseases due to frequent contact with domestic and wild animals, and restricted access to health care. Limited disease surveillance in remote rural areas is a crucial gap in global health security. Although this point has been made in the past, practical solutions on how to implement surveillance efficiently in these resource-limited and logistically challenging settings have yet to be discussed. We highlight why investing in disease surveillance in remote rural areas of low-income and middle-income countries will benefit the global community and review current approaches. Using semi-arid regions in Kenya as a case study, we provide a practical approach by which surveillance in remote rural areas can be strengthened and integrated into existing systems. This Viewpoint represents a transition from simply highlighting the need for a more holistic approach to disease surveillance to a solid plan for how this outcome might be achieved.
Intra- and inter-specific resource partitioning within predator communities is a fundamental component of trophic ecology, and one proposed mechanism for how populations partition resources is through individual niche variation. The Niche Variation Hypothesis (NVH) predicts that inter-individual trait variation leads to functional trade-offs in foraging efficiency, resulting in populations composed of individual dietary specialists. The degree to which niche specialization persists within a population is plastic and responsive to fluctuating resource availability. We quantified niche overlap and tested the NVH within an Arctic raptor guild, focusing on three species that employ different foraging strategies: golden eagles (generalists); gyrfalcons (facultative specialists); and rough-legged hawks (specialists). Tundra ecosystems exhibit cyclic populations of arvicoline rodents (lemmings and voles), providing a unique system in which to examine predator diet in response to interannual fluctuations in resource availability. Using blood δ¹³C and δ¹⁵N values from 189 raptor nestlings on Alaska’s Seward Peninsula (2014–2019), we calculated isotopic niche width and used Bayesian stable isotope mixing models (BSIMMs) to characterize individual specialization and test the NVH. Nest-level specialization estimated from stable isotopes was strongly correlated with indices of specialization based on camera trap data. We observed a high degree of isotopic niche overlap between the three species and gyrfalcons displayed a positive relationship between individual specialization and population niche width on an interannual basis consistent with the NVH. Our findings suggest plasticity in niche specialization may reduce intra- and inter-specific resource competition under dynamic ecological conditions.
Optimal reproductive performance occurs when birds time reproduction to coincide with peak food availability. Deviation from optimal timing, or mismatch, can affect productivity, though birds may mediate some mismatch effects by altering their incubation behavior. We studied the consequences of nesting timing (i.e., clutch initiation relative to an index of spring start) on productivity across the breeding range of American kestrels (Falco sparverius) in the United States and southern Canada, and associations between nesting timing, incubation behavior, and hatching asynchrony. We used observations from long-term nest box monitoring, remote trail cameras, and community-scientist-based programs to obtain data on clutch initiation, productivity, incubation, and hatching synchrony. Kestrels that initiated clutches after the extended spring index (SI-x, start of spring estimate) had higher rates of nest failure and fewer nestlings than earlier nesters, and effects of nesting timing on productivity were strongest in the Northeast. In contrast, kestrels in the Southwest experienced a more gradual decline in productivity across the season. Spatial effects may be the result of regional differences in growing seasons and temporal nesting windows (duration of nesting season). Specifically, resource availability in the Northeast was highly peaked during the breeding season, potentially resulting in shorter nesting windows. Conversely, resource curves were more prolonged in the Southwest, and growing seasons are becoming longer with climate change, potentially resulting in longer nesting windows. We found an inverse relationship between nesting timing and the onset of male incubation. Males from breeding pairs that initiated clutches after SI-x began incubation sooner than males from breeding pairs that initiated clutches before SI-x. Early-onset of male incubation was positively associated with hatching asynchrony, creating increased age variation in developing young. In sum, nesting phenology relative to the SI-x has consequences for American kestrels’ productivity, and these consequences vary across space. Also, the early onset of incubation may act as a potential adaptive behavior to advance the average hatch date and spread out energetic demands. Given the effects of nesting timing on productivity, kestrels are likely to be sensitive to climate-driven advances in growing seasons and vulnerable to phenological mismatch, particularly in the Northeast.
The Rufous-legged Owl (Strix rufipes) is the southernmost Strix owl species and its breeding ecology remains little known. We report new observations on the species' breeding ecology, including clutch size, egg size, duration of the incubation and nestling periods, and nestling diet. We conducted our observations on nests found during the summers of 1999 through 2004 in a forestry landscape of central Chile, dominated by Monterey pine (Pinus radiata) plantations with intermixed fragments of native southern beech (Nothofagus) forests. Clutch size was two eggs (n = 2 nests), with one egg larger than the other (mean = 48.8 × 40.1 mm). The incubation period was 30 d and the nestling period 34 d. We analyzed 10 pellets from nestling owls and identified 45 prey items, mostly dominated by large beetles, grasshoppers, and rodents (native and exotic). This information, though based on a limited number of nests, provides baseline ecological data that can inform future studies.
Scoping reviews, in which the literature on a given topic is systematically collated and summarized, aid literature searches and highlight knowledge gaps on a given topic, thus hastening scientific progress and informing conservation efforts. Because much research and conservation is targeted at the species level, ornithology and bird conservation would benefit from scoping reviews of individual species. We present and apply a framework for scoping reviews for three disparate raptor species: California Condor Gymnogyps californianus, Harpy Eagle Harpia harpyja and Gyrfalcon Falco rusticolus. We consulted expert panels to develop appropriate search strings and lists of essential literature, i.e. ‘benchmark articles’. We searched Web of Science, Scopus and Google Scholar. Searches for California Condor, Harpy Eagle and Gyrfalcon returned 268, 138 and 343 articles, respectively, that discuss, review or collect empirical data for the focal species. Our searches returned all benchmark articles identified by species experts, indicating that the searches captured the most important work on each species. We coded each study according to the topic addressed, country and month in which data were collected. We also coded threats, stresses and conservation actions addressed by studies, following definitions used by the International Union for the Conservation of Nature (IUCN) during Red List assessments. Literature summaries for each species include the number of studies addressing certain topics, monthly timing of research and global maps of research focus. Our coding scheme revealed important knowledge gaps for each species. Effects of conservation actions on wild individuals were less studied for California Condors. Harpy Eagles were less studied outside of Brazil and Panama, and Gyrfalcons were less studied outside of their breeding season. Scoping reviews of the world's bird species would help to identify critical knowledge gaps, thereby aiding the global effort to assuage the sixth mass extinction.
Kenya's wildlife has been declining substantially for decades, due to rapid human population growth and its associated impacts on natural habitats. Predators and scavengers are particularly sensitive to anthropogenic pressures, and their changing status has corresponding impacts on the ecosystem services they provide. To estimate rates of change in Kenya's raptor populations we compared linear encounter rates (individuals 100 km − 1) recorded during road surveys conducted in 1970-1977 and 2003-2020. Encounter rates for 19 out of 22 species examined had fallen, by a median of 70% among those showing a significant or near-significant change. No species had increased significantly. Declines had occurred among all vulture and large eagle species, and were especially pronounced among once-common small and medium-sized raptors. Our findings demonstrate the importance of protected areas (PAs) for Kenya's remaining raptor populations. The median encounter rate for vultures and large eagles had dropped by 23% within PAs and by 76% in unprotected areas. Smaller species showed divergent trends in relation to PA status, their median encounter rate increasing by 104% within PAs while declining by 85% elsewhere. Based on projected declines over three generation lengths, 45% of the species examined would qualify as nationally Endangered or Critically Endangered. Key threats include electrocution/collision with energy infrastructure, deliberate and incidental poisoning, and impacts associated with habitat degradation. Kenya's raptor declines could be reversed through enhanced management of PAs, mitigation of specific threats and the implementation of species recovery plans; all requiring steadfast government commitment and close collaboration with conservation stakeholders.
Illegal wildlife crime is a global phenomenon, accelerating the ongoing biodiversity crisis. In the Old World, and particularly in Africa, illegal use of poisons to eliminate carnivores is the main driver of the continental vulture crisis. Knowledge about the underlying source and drivers of this threat is lacking for most areas, including Kenya, a global vulture and biodiversity hotspot. An extensive questionnaire survey of over 1300 respondents was run, using a specialized questioning technique and quantitative analytical approaches. Results show that, while pastoralists have a positive attitude towards vultures, over 20% of them use poisons to eliminate predators. Poisoning was largely driven by livestock losses to predators, and by negative attitude towards predators. Poisoning was less prevalent among respondents aware of the Kenya Wildlife Act. Overall, we suggest that a combination of top-down, e.g. legislation, and bottom-up (such as corrals or compensation) along with awareness campaigns may help reduce poisoning on the ground.
Due to an abundance and diversity of vultures, Nepal is one of the most important countries for vulture conservation. Within Nepal, the Pokhara Valley is especially significant. We examine the distribution of vultures within the Pokhara Valley by conducting counts at 11 potential feeding or roosting sites using point count method. We further surveyed people of the valley regarding their perception of vulture ecology and conservation, knowledge of diclofenac use within the valley, and burial of livestock carcasses. We detected eight species of vultures, four of which are currently threatened with extinction. White-rumped vulture Gyps bengalensis, Egyptian vulture Nephron percnopterus, and Himalayan vulture G. himalayensis were the most abundant. Almost all respondents (98%) had sighted the vultures in the wild. Formally educated respondents reported seeing vultures’ slightly more than non-formally educated respondents. Fifty eight percent respondents suspected habitat loss was the major threat for the vulture population decline in Pokhara Valley, and 97% respondents were not aware of any diclofenac use. The knowledge of vultures in people with different age groups suggests a more awareness programs are needed for local people, especially those who carry out animal husbandry and provide livestock to the vulture restaurant.
Tourism can be a powerful tool for wildlife conservation if well controlled and responsibly managed. Apex predators constitute particularly attractive subjects for tourism, but simultaneously they may generate conflict with local communities. Harpy Eagles Harpia harpyja are the largest eagle species and are highly sought-after by ecotourists. The last stronghold of the Harpy Eagle is the Amazon Forest, which is being deforested for cattle ranching. We tested methods for developing Harpy Eagle ecotourism as a potential tool to harmonize these issues. Using camera traps, we collected data on timing of Harpy Eagle visits to their nests, as well as on probabilities of viewing an eagle. Harpy Eagles can only be seen predictably during the first 12 of the 30–36 month nest cycle. In nests with nestlings (up to 5–7 months), adults are visible on a daily basis, and this period lasts 16.6% of the nesting cycle, demanding a minimum of 13, 17, and 26 nests to have at least one nest with a nestling on 90%, 95% and 99% of the days. After this 5–7 month window, we found that two and 4.16 days spent at nests afforded high probabilities of sighting a fledgling or adult eagle, respectively. Harpy Eagles were mainly active at the beginning and the end of the day. Activity core lasted 6.5 decimal hours for adults, peaking at 10h00, and 7.45 decimal hours for fledged eagles, peaking at 15h00. Our results demonstrate that Harpy Eagles fit several criteria for a viable wildlife attraction: predictable in activity and location, viewable, and diurnal, even though at the same time they are considered a rarity. In a broader perspective, Harpy Eagle tourism shows every indication of being a significant tool for more robust rainforest conservation.
The effects of forest fragmentation on forest bird species in the Bemanevika Protected Area (PA), northwestern Madagascar, were investigated during two breeding seasons from October 2016 to January 2018. The forest of Bemanevika is composed of large patches of fragmented tropical rainforest. Seven forest fragments ranging from 10 to 1 050 ha were surveyed. Two methods were used to collect data along transects orientated from the forest edge toward the interior of the forest: mist-netting and point-counts. In all, 27 non-forest birds and 65 forest birds were recorded at all fragments. According to their distribution along an edge-interior gradient, these 65 forest species are classified into three main groups: 15 (23.1%) edge species, 12 (18.5%) forest interior species and 38 (58.5%) ubiquitous species. Larger forest fragments host more forest bird species than smaller forest fragments. Of the 65 forest birds, 14, including the 12 forest interior species, were not found in the four smaller fragments (10–29 ha). The density of forest interior species was positively correlated to forest fragment size. The general trend was that forest interior species were the most sensitive to forest fragmentation (e.g. Madagascar Serpent-eagle Eutriorchis astur, Pitta-like Ground-roller Atelornis pittoides and Schlegel’s Asity Philepitta schlegeli). Large raptors, terrestrial species and understory species were the first to disappear from the small fragments. Fragmented forests provide habitat for bird species, even for those vulnerable to forest fragmentation, therefore the maintenance of large enough forest fragments should be considered in all conservation strategies aimed to protect forest birds.
Species assemblages often have a non‐random nested organization, which in vertebrate scavenger (carrion‐consuming) assemblages is thought to be driven by facilitation in competitive environments. However, not all scavenger species play the same role in maintaining assemblage structure, as some species are obligate scavengers (i.e., vultures) and others are facultative, scavenging opportunistically. We used a database with 177 vertebrate scavenger species from 53 assemblages in 22 countries across five continents to identify which functional traits of scavenger species are key to maintaining the scavenging network structure. We used network analyses to relate ten traits hypothesized to affect assemblage structure with the ‘role’ of each species in the scavenging assemblage in which it appeared. We characterized the role of a species in terms of both the proportion of monitored carcasses on which that species scavenged, or scavenging breadth (i.e., the species ‘normalized degree’), and the role of that species in the nested structure of the assemblage (i.e., the species ‘paired nested degree’), thus identifying possible facilitative interactions among species. We found that species with high olfactory acuity, social foragers, and obligate scavengers had the widest scavenging breadth. We also found that social foragers had a large paired nested degree in scavenger assemblages, probably because their presence is easier to detect by other species to signal carcass occurrence. Our study highlights differences in the functional roles of scavenger species and can be used to identify key species for targeted conservation to maintain the ecological function of scavenger assemblages.
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