Cerulean Warblers in the Ozark region: habitat selection,breeding biology,survival, and space use

Cerulean Warblers (Setophaga cerulea) are a species with declining populations that exhibit regional variation in habitat selection and demographic rates. The Ozark region of the south‐central United States likely provides important habitat for Cerulean Warblers, but little is known about their breeding biology in that region. We studied Cerulean Warblers in riparian forests of the Ozarks of Arkansas from 2018 to 2020. We assessed multi‐scale habitat selection for vegetative and topographic features, documented their breeding biology, estimated within‐season and annual apparent survival, and estimated territory sizes. We found that Cerulean Warblers selected riparian habitat characterized by large‐diameter trees across all spatial scales. Contrary to the results of previous studies, males appeared to avoid white oaks (Quercus spp., Section Quercus) at the territory scale, but this avoidance may reflect an underlying preference for riparian habitat. Our logistic‐exposure estimate of nest survival (0.32; 85% confidence interval: 0.21–0.46) was similar to the median of estimates reported in previous studies. Our results indicate that maintaining riparian forests with large trees is important to provide suitable habitat for Cerulean Warblers in the Ozark region. Because of similarities in habitat selection among regions, some management practices from other populations, including retaining large trees and promoting a heterogeneous canopy structure, may be useful for managing for Cerulean Warblers in riparian areas of the Ozarks. However, selection for topography and tree species by Cerulean Warblers in our study also suggests that region‐specific management strategies will be beneficial. Finally, our demographic rate estimates for this population should prove valuable in future full‐annual‐cycle population modeling efforts.     

Crosswise migration by Yellow Warblers,Nearctic‐Neotropical passerine migrants

Yellow Warblers (Setophaga petechia) are abundant breeding birds in North America, but their migratory and non‐breeding biology remain poorly understood. Studies where genetic and isotopic techniques were used identified parallel migration systems and longitudinal segregation among eastern‐ and western‐breeding populations of Yellow Warblers in North America, but these techniques have low spatial resolution. During the 2015 breeding season, we tagged male Yellow Warblers breeding in Maine (N = 10) and Wisconsin (N = 10) with light‐level geolocators to elucidate fine‐scale migratory connectivity within the eastern haplotype of this species and determine fall migration timing, routes, and wintering locations. We recovered seven of 20 geolocators (35%), including four in Maine and three in Wisconsin. The mean duration of fall migration was 49 d with departure from breeding areas in late August and early September and arrival in wintering areas in mid‐October. Most individuals crossed the Gulf of Mexico to Central America before completing the final eastward leg of their migration to northern South America. Yellow Warblers breeding in Maine wintered in north‐central Colombia, west of those breeding in Wisconsin that wintered in Venezuela and the border region between Brazil, Colombia, and Venezuela. Our results provide an example of crosswise migration, where the more easterly breeding population wintered farther west than the more westerly breeding population (and vice versa), a seldom‐documented phenomenon in birds. Our results confirm earlier work demonstrating that the eastern haplotype of northern Yellow Warblers winters in northern South America, and provide novel information about migratory strategies, timing, and wintering locations of birds from two different populations.     

Extreme genetic similarity does not predict non‐breeding distribution of two closely related warblers

Detailed knowledge of migratory connectivity can facilitate effective conservation of Neotropical migrants by helping biologists understand where and when populations may be most limited. We studied the migratory behavior and non‐breeding distribution of two closely related species of conservation concern, the Golden‐winged Warbler (Vermivora chrysoptera) and Blue‐winged Warbler (Vermivora cyanoptera). Although both species have undergone dynamic range shifts and population changes attributed to habitat loss and social interactions promoting competition and hybridization, full life‐cycle conservation planning has been limited by a lack of information about their non‐breeding ecology. Because recent work has demonstrated that the two species are nearly identical genetically, we predicted that individuals from a single breeding population would have similar migratory timing and overwintering locations. In 2015, we placed light‐level geolocators on 25 males of both species and hybrids in an area of breeding sympatry at the Fort Drum Military Installation in Jefferson and Lewis counties, New York. Despite extreme genetic similarity, non‐breeding locations and duration of migration differed among genotypes. Golden‐winged Warblers (N = 2) overwintered > 1900 km southeast of the nearest Blue‐winged Warbler (N = 3) and spent nearly twice as many days in migration; hybrids (N = 2) had intermediate wintering distributions and migratory timing. Spring migration departure dates were staggered based on distance from the breeding area, and all birds arrived at the breeding site within 8 days of each other. Our results show that Golden‐winged Warblers and Blue‐winged Warblers in our study area retain species‐specific non‐breeding locations despite extreme genetic similarity, and suggest that non‐breeding locations and migratory timing vary along a genetic gradient. If the migratory period is limiting for these species, our results also suggest that Golden‐winged Warblers in our study population may be more vulnerable to population decline than Blue‐winged Warblers because they spend almost twice as many days migrating.     

Remote estimation of overwintering home ranges in an elusive,migratory nocturnal bird

Due to a long running research bias toward the breeding season, there are major gaps in knowledge on the basic nonbreeding ecology of many species, preventing a full‐annual cycle focus in ecology and conservation. Exacerbating this problem is the fact that many species are extremely difficult to detect outside of breeding. Here, we demonstrate a partial solution to this problem by using archival GPS tags to examine the overwintering ecology of a migratory nocturnal bird, the eastern whip‐poor‐will (Antrostomus vociferous). We deployed tags on 21 individuals and were able to recover 11 (52%) one year later. Tags collected high precision (approx. 10 m) points throughout the nonbreeding period. With continuous time movement models, we used these data to estimate overwintering home ranges. All individuals exhibited at least one bounded home range during this phase of the annual cycle, three of eleven had two wintering locations, and home range area ranged from 0.50 to 10.85 ha. All overwintering home ranges contained closed‐canopy forest land cover (42%–100%), and no other land cover type represented >40% of any home range. We found some evidence, with caveats, that total edge within the landscape surrounding the home range was negatively related to home range area. The prevalence of contiguous closed‐canopy forest cover in overwintering home ranges contrasts with apparent breeding habitat preferences, which includes clear‐cuts and other, more open, habitats. This study is the first to reveal key aspects of overwintering space use in this species by using archival GPS to overcome both logistical and methodological limitations. Expanded use of such technology is critical to gathering basic ecological and distributional data, necessary for achieving a more complete understanding of full‐annual cycles of animal populations.     

Spatial ecology of bluetongue lizards (Tiliqua spp.) in the Australian wet–dry tropics

New technologies for quantifying animal locations enable us to document habitat‐selection patterns of cryptic taxa in extraordinary detail. Northern bluetongues (Tiliqua scincoides intermedia) and centralian bluetongues (Tiliqua multifasciata) are large heavy‐bodied scincid lizards that are broadly sympatric in the wet–dry tropics of north‐western Australia. We used data from GPS‐based radiotelemetry (n = 49 lizards, tracked for 2–121 days, total n = 61 640 locations) to examine the size, internal structure and overlap of lizard home ranges. Despite substantial habitat differences at our two study sites (semi‐arid and relatively pristine habitat at Keep River National Park, Northern Territory, vs. highly disturbed and fragmented flood plain habitat in an agricultural area near Kununurra, Western Australia), home ranges were similar between the two areas, and between the two species. Our radio‐tracked lizards continued to disperse into previously unused areas throughout the duration of the study, so that the total areas used by lizards continued to increase. Based on the minimum convex polygon method, total home ranges averaged 4 ha (range 2–12 ha), but only about two‐thirds of each home range was used intensively. Each home range had multiple core areas, and overlap of core as well as peripheral areas (especially with same‐sex conspecifics) was high at the disturbed (Western Australia) site where lizard densities were high. The concentration of lizard activity within small core areas, often used by multiple individuals, suggests that these heavily used sites are critical to lizard conservation. However, the lizards' infrequent long‐distance displacements also make them vulnerable to changes in the wider landscape mosaic. Because GPS‐based radiotelemetry can quantify habitat use at finer spatial and temporal scales than earlier technologies, it can provide a robust base for management of at‐risk fauna.     

Time and travelling costs during chick‐rearing in relation to habitat quality in Little Owls Athene noctua

In many bird species, parents adjust their home‐ranges during chick‐rearing to the availability and distribution of food resources, balancing the benefits of energy intake against the costs of travelling. Over recent decades, European agricultural landscapes have changed radically, resulting in the degradation of habitats and reductions in food resources for farmland birds. Lower foraging success and longer foraging trip distances that result from these changes are often assumed to reduce the reproductive performance of parents, although the mechanisms are not well understood. We tested the behavioural response of chick‐rearing Little Owls Athene noctua to variation in habitat diversity in an agricultural landscape. We equipped females with GPS loggers and received adequate range‐use data for 19 individuals (6063–14 439 locations per bird). In habitats dominated by homogeneous cropland habitats, home‐ranges were over 12 ha in size, whereas in highly diverse habitats they were below 2 ha. Large home‐ranges were associated with increased flight activity (117% of that of birds in small home‐ranges) and distances travelled per night (152%), increased duration of foraging trips (169%) covering larger distances (246%), and reduced nest visiting rates (81%). The study therefore provides strong correlative evidence that Little Owls breeding in monotonous farmland habitats expend more time and energy for a lower benefit in terms of feeding rates than do birds in more heterogeneous landscapes. As nestling food supply is the main determinant of chick survival, these results suggest a strong impact of farmland characteristics on local demographic rates. We suggest that preserving and creating islands of high habitat diversity within uniform open agricultural landscapes should be a key target in the conservation of Little Owl populations.     

Precise direct tracking and remote sensing reveal the use of forest islands as roost sites by Purple Martins during migration

Direct tracking methods in combination with remote sensing data allow examination of habitat use by birds during migration. Species that roost communally during migration, such as some swallows, form large aggregations that can attract both avian and terrestrial predators. However, the extent to which they might use patchy habitats that could reduce predation risk during migration is unknown. We tested the hypothesis that Purple Martins (Progne subis) use forest islands (patches of suitable forest habitat surrounded by unsuitable habitat) as roost sites during migration between breeding sites in North America and overwintering sites in South America. We used high‐precision (< 10 m), archival GPS units deployed and retrieved during the 2015 and 2016 breeding seasons, respectively, at 12 colonies located across eastern North America. We found that Purple Martins roosted in forest islands more often than expected based on availability during both spring and fall migration. Despite an apparent association with urban habitats by Purple Martins based on observational and radar data in North America during the fall, the roost locations we identified during spring and fall migration were not more closely associated with urban areas than random locations. The use of forest islands during both spring and fall migration suggest that Purple Martins may use these habitats to reduce predation risk during migration. Our results suggest that some species of birds may use similar habitats as stopover sites during migration and that patches of forest habitat may be important conservation targets for Purple Martins and other species. Identifying habitat use during migration represents an important advance in support of full annual‐cycle conservation of Purple Martins and other migratory species with declining populations.     

Foraging behavior of migrant warblers in mixed‐species flocks in Venezuelan shade coffee: interspecific differences,tree species selection,and effects of drought

Shade coffee has been identified as an important habitat for Nearctic‐Neotropical migrants during the non‐breeding season, including species of conservation concern such as Cerulean Warblers (Setophaga cerulea). To better understand habitat features important for migrants in shade coffee, we studied the foraging behavior of migrants in mixed‐species flocks at six shade‐coffee farms in the Cordillera de Merida, Venezuela, in 2008–2009 and the El Niño drought year of 2009–2010. We examined interspecific differences in foraging behavior and tree species selection of three foliage‐gleaning migrants, Blackburnian (Setophaga fusca), Cerulean, and Tennessee (Oreothlypis peregrina) warblers, and aerial‐foraging American Redstarts (Setophaga ruticilla). For morphologically similar Blackburnian and Cerulean warblers, we also examined factors influencing foraging rates (attack and movement rates), capture of large prey, and maneuver/substrate type. We found that aerial‐foraging American Redstarts foraged lower, used more aerial maneuvers, showed no tree species selection, and were less likely to forage in flocks than foliage‐gleaners. Although foraging rates were similar for Blackburnian and Cerulean warblers, the three foliage‐gleaners differed in foraging height and use of maneuvers. Cerulean Warblers foraged lower than the other two species, whereas Blackburnian Warblers used the greatest proportion of woody gleans. All three foliage‐gleaners selected Inga spp. (a commonly planted shade tree in shade‐coffee farms) for foraging, and Blackburnian and Cerulean warblers captured a greater proportion of large prey in Inga spp. than in other tree species. During the drought year, Blackburnian and Cerulean warblers captured half as many large prey and used a greater proportion of woody‐gleans. We found that interactions among behavioral, floristic, and environmental drivers influenced the foraging behavior of migrants wintering in shade coffee. Our results support those of previous studies suggesting that migrants partition resources behaviorally during the non‐breeding season, that foliage‐gleaners may benefit from the presence of shade trees, especially Inga spp., in agroforestry systems, and that drought may influence the foraging behavior of foliage‐gleaning migrants, presumably due to reduced prey availability.     

Predation risk and resource availability explain roost locations of Whimbrel Numenius phaeopus in a tropical mangrove delta

Roosts are important sites for shorebirds in non‐breeding areas at night and during high tides. How the spatial configuration of food and risk of predation and disturbance influence roost site use in tropical locations remains poorly known. We analysed the locations of nocturnal roosts of Whimbrel Numenius phaeopus in mangroves of Sanquianga National Park, Colombia, with respect to variation in spatial variables related to food resources and risk of predation and disturbance. We contrasted characteristics of all 13 known nocturnal roost locations with those of all other mangrove islands (n = 209) within the limits of the park. We estimated the distance from roosts and other mangrove islands to foraging sites, and sources of predators and human disturbance. Larger areas of feeding habitat surrounded nocturnal roosts than other mangrove islands, and the average distance to individual feeding patches was shorter. Roosts were also more isolated than other islands, but proximity to sources of human disturbance did not differ. We conclude that Whimbrel roost site use in Sanquianga was best explained by a combination of access to feeding territories and isolation from potential sources of mainland predators, but not by avoidance of human disturbance. Beyond identifying factors influencing roost site selection, the large aggregations of individuals in single locations may suggest that presence of conspecifics itself also plays a role in the formation of Whimbrel roosts. We highlight the interaction of food and risk landscapes with intraspecific attraction on the roost site selection by Whimbrels and the importance of mangroves as roosting sites in tropical regions.     

Home‐ranges,population densities,vocal behavior,and post‐fledging movements of Cipo Canasteros (Asthenes luizae,Furnariidae), a rock‐specialist endemic of the highlands of eastern Brazil

Cipo Canasteros (Asthenes luizae, Furnariidae) have a fragmented and limited range restricted to the campos rupestres (rupestrian grasslands) habitat in the Brazilian highlands of the Espinhaço Range, and little is known about their behavior, ecology, and population biology. From March 2009 to November 2010, we monitored birds (24 banded and 22 radio‐tracked) at two study sites at Serra do Cipó in the state of Minas Gerais, Brazil, to estimate their home‐range sizes and population density, and describe their habitat use, natal dispersal behavior, and vocal behavior. We found an average density of 8.7 paired adults/km² in our study areas or 22.9 paired adults/km² when considering only used habitats. The sex ratio was male‐biased (males/total adults = 0.68), adults exhibited high site fidelity, home‐ranges averaged 4.0 ha (fixed kernel 95%) or 3.5 ha (95% minimum convex polygon) in size, and both sexes defended territories year‐round. We recorded four main types of songs, including two uttered more often during the breeding season. We monitored the natal dispersal of two males and one female who moved maximum distances of 1238 m, 780 m, and 1056 m, respectively, from natal areas. Our results confirm that Cipo Canasteros are restricted to the rocky‐outcrop habitat of the campos rupestres. In part due to their habitat specialization, Cipo Canasteros are considered Near Threatened, but other factors contributing to their demographic fragility include the small number, and probably low survival, of females and low reproductive success due to predation and brood parasitism by cowbirds. Given these threats, along with their specialized habitat and restricted range, the future conservation of Cipo Canasteros will likely depend on the extent to which their campos rupestres habitat can be conserved.     

Multi-Scale Assessment of Male Northern Yellow Bat Roost Selection

Knowledge of roost selection by northern yellow bats (Lasiurus intermedius) is limited to a small number of known roost locations. Yet knowledge of basic life history is fundamental to understanding past response to anthropogenic change and to predict how species will respond to future environmental change. Therefore, we examined male northern yellow bat roost selection on 2 Georgia, USA, barrier islands with different disturbance histories. Sapelo Island has a history of extensive disturbance and is dominated by pine (Pinus spp.) forests; Little Saint Simons Island has a limited disturbance history with maritime oak (Quercus spp.) forest as the dominant cover type. From March–July 2012 and 2013, we radio-tracked 35 adult male northern yellow bats to diurnal roosts and modeled roost characteristics at the plot and landscape scales. We located 387 roosts, of which 95% were in Spanish moss (Tillandsia usneoides) hanging in hardwood trees. On both islands, bats selected roost trees with larger diameters than surrounding trees and selected roost locations with greater open flight space (i.e., low midstory clutter) underneath. Roosts were located farther from open areas on Sapelo and closer to fresh water on Little Saint Simons compared to random locations. Lower availability of hardwood forest on Sapelo may have resulted in small-scale roost site selection (i.e., plot level) despite potential increased costs of commuting to water and open areas for foraging. In contrast, greater availability of hardwood forest on Little Saint Simons likely allowed selection of roosts closer to fresh water, which provides foraging and drinking opportunities. Our results indicate that mature hardwood trees in areas with low midstory clutter are important in male northern yellow bat roost selection, but landscape-level features have varying influences on roost selection, likely as a result of differences in disturbance history. Therefore, management will differ depending on the landscape context. Further research is needed to examine roost selection by females, which may have different habitat requirements. © 2020 The Wildlife Society.     

Seasonal home range dynamics and sex differences in habitat use in a threatened,coastal marsh bird

A comprehensive understanding of spatiotemporal ecology is needed to develop conservation strategies for declining species. The king rail (Rallus elegans) is a secretive marsh bird whose range historically extended across the eastern United States. Inland migratory populations have been greatly reduced with most remaining populations inhabiting the coastal margins. Our objectives were to determine the migratory status of breeding king rails on the mid‐Atlantic coast and to characterize home range size, seasonal patterns of movement, and habitat use. Using radiotelemetry, we tracked individual king rails among seasons, and established that at least a segment of this breeding population is resident. Mean (±SE) home range size was 19.8 ± 5.0 ha (95% kernel density) or 2.5 ± 0.9 (50% kernel density). We detected seasonal variation and sex differences in home range size and habitat use. In the nonbreeding season, resident male home ranges coincided essentially with their breeding territories. Overwintering males were more likely than females to be found in natural emergent marsh with a greater area of open water. Females tended to have larger home ranges than males during the nonbreeding season. We report for the first time the use of wooded natural marsh by overwintering females. Brood‐rearing king rails led their young considerable distances away from their nests (average maximum distance: ~600 ± 200 m) and used both wooded natural and impounded marsh. King rails moved between natural marsh and managed impoundments during all life stages, but the proximity of these habitat types particularly benefitted brood‐rearing parents seeking foraging areas with shallower water in proximity to cover. Our results demonstrate the importance of interspersion of habitat types to support resident breeders. Summer draining of impounded wetlands that are seasonally flooded for wintering waterfowl allows regrowth of vegetation and provides additional habitat at a critical time for wading birds.     

Post‐breeding population dynamics indicate upslope molt‐migration by Wilson's Warblers

Molt is an energetically costly process, and songbirds (Order Passeriformes) exhibit a diversity of strategies to maximize their survival and reproductive success while meeting the energetic demands of the annual prebasic molt. Nearctic‐Neotropic migrants in western North America commonly exhibit one of three strategies: (1) remain in breeding areas to molt, (2) migrate long distances to molt before continuing to wintering areas, or (3) migrate to wintering areas and then molt. Among species that molt in or near breeding areas, the nature of small‐scale movements to undergo molt remains largely unknown. We used banding data collected over a period of 27 yr and across an elevational gradient to examine the propensity of Wilson's Warblers (Cardellina pusilla) to molt and breed at the same or different locations in northern California and southern Oregon. We found that individual adult Wilson's Warblers were more likely to breed at lower elevations and molt at higher elevations, suggesting that some individuals move altitudinally after breeding to complete the definitive prebasic molt. Such altitudinal movements may be more common among Nearctic‐Neotropic migrants in western North America than previously thought.     

An improved survey method for monitoring population trends of Golden‐winged Warblers and other patchily distributed birds

Conventional surveys designed to monitor common and widespread species may fail to adequately track population changes of rare or patchily distributed species that are often of high conservation concern. We evaluated the performance of a new monitoring approach that employs both a spatially balanced sampling design and a targeted survey protocol designed to estimate population trends of one such patchily distributed species, the Golden‐winged Warbler (Vermivora chrysoptera), in the Appalachian Mountains Bird Conservation Region (BCR 28), USA. Our spatially balanced survey consisted of 105 sample quads (one‐quarter Delorme Atlas pages) across the current range of Golden‐winged Warblers within BCR 28, each with five sample points located in early successional habitat. From 2009 to 2013, collaborators visited each sample point once per year during the peak breeding season and conducted a 17‐min survey consisting of passive observation and playback of conspecific songs and mobbing vocalizations. We used multi‐season, single‐species occupancy models to estimate probability of quad occupancy, detection probability, and occupancy dynamics for Golden‐winged Warblers and closely related Blue‐winged Warblers (Vermivora cyanoptera). Our survey protocol resulted in high estimates of detection probability for Golden‐winged (92%) and Blue‐winged (79%) warblers, with 47% and 56% of quads estimated to be initially occupied, respectively. Derived population trend estimates (λ) indicated an average decline in population of 6% for Golden‐winged Warblers and 7% for Blue‐winged Warblers, resulting in estimated 21% and 22% declines, respectively, in quad occupancy after 5 yr. Our results demonstrate that coupling a spatially balanced survey design in appropriate habitat with a playback protocol to increase detection rates is a viable strategy for tracking populations of Golden‐winged Warblers in the Appalachian Mountains BCR. Similar survey methods should be considered for other rare, declining, or patchily distributed bird species that require targeted monitoring.     

Foraging behavior of Cerulean Warblers during the breeding and non‐breeding seasons: evidence for the breeding currency hypothesis

Birds require additional resources for raising young, and the breeding currency hypothesis predicts that insectivorous species exploit large soft‐bodied prey during the breeding season, but shift to small, likely hard‐bodied, prey during the non‐breeding season. To test this hypothesis, we examined prey use by Cerulean Warblers (Setophaga cerulea), foliage‐gleaning Nearctic‐Neotropical migrants, during the breeding and non‐breeding seasons. We collected data on foraging behavior during the breeding season (including observations of prey items fed to young) in upland mixed‐oak forest in southeastern Ohio in 2009 and 2010 and, during the non‐breeding season, in shade coffee in the Cordillera de Merida, Venezuela, in 2008–2009. Cerulean Warblers captured 7% more large prey (visible prey extending beyond the bill) during the breeding than the non‐breeding season, but foraged at similar rates during both seasons. Large, soft‐bodied prey appeared to be especially important for feeding young. We found that adults delivered large prey on >50% of provisioning visits to nests and 69% of identifiable large prey fed to nestlings were greenish larvae (likely Lepidoptera or caterpillars) that camouflage against leaves where they would tend to be captured by foliage‐gleaning birds. Availability of specific taxa appeared to influence tree species foraging preferences. As reported by other researchers, we found that Cerulean Warblers selected trees in the genus Carya for foraging and our examination of caterpillar counts from the central Appalachian Mountains (Butler and Strazanac 2000 ) showed that caterpillars with greenish coloration, especially Baileya larvae, may be almost twice as abundant on Carya than Quercus. Our results provide evidence for the breeding currency hypothesis, and highlight the importance of caterpillars to a foliage‐gleaning migrant warbler of conservation concern.     

Identifying key habitats for the conservation of Bonelli's Eagle Aquila fasciata using radiotracking

Identifying the priority habitats of endangered species is crucial to implementing effective conservation actions. We characterize the key habitats used by Bonelli's Eagle Aquila fasciata, an umbrella and flagship species that is endangered in Mediterranean countries. We radiotracked 17 breeding individuals (10 males and seven females) in Catalonia (NE Iberian Peninsula) and used compositional analysis to determine the key habitats in home‐ranges of both sexes. The main habitats identified within the home‐range area were scrubland, coniferous forests, cropland, sclerophyllous forests, rock outcrops and urban areas, with little difference in habitat use between the sexes. Bonelli's Eagles preferred rocky habitats as breeding areas and scrubland as foraging areas, as these hold the highest abundance of their main prey, Rabbits Oryctolagus cuniculus and Red‐legged Partridges Alectoris rufa. Habitat selection varied seasonally in foraging areas: scrubland was the most preferred habitat type during the breeding season, whereas rocky areas were preferred during the non‐breeding season (although scrubland was also highly selected). Urban areas were avoided both as breeding and as foraging areas. Home‐range size was inversely correlated with the proportion of scrubland, suggesting that this is a key habitat for Bonelli's Eagle. To conserve this species effectively, policies that ensure the preservation of the cliffs used as breeding sites, as well as suitable management of the scrubland used for foraging, should be implemented in the areas inhabited by this species. The promotion of traditional land uses and management techniques that will enhance open areas in Mediterranean landscapes should in the future play an essential role in the conservation of Bonelli's Eagle in Mediterranean habitats.     

Conservation status assessment of the Sharp‐shinned Hawk,an endangered insular raptor in Puerto Rico

Sharp‐shinned Hawks (Accipiter striatus) are forest raptors that are widely distributed in the Americas. A subspecies endemic to Puerto Rico (A. s. venator) is listed as endangered and restricted to mature and old secondary montane forests and shade coffee plantations. However, recent information about the population status and distribution of Puerto Rican Sharp‐shinned Hawks is lacking. We developed a spatial geographic distribution model for Sharp‐shinned Hawks in Puerto Rico from 33 locations collected during four breeding seasons (2013–2016) using biologically relevant landscape variables (aspect, canopy closure, elevation, rainfall, slope, and terrain roughness). Elevation accounted for 89.8% of the model fit and predicted that the greatest probability of occurrence of Sharp‐shinned Hawks in Puerto Rico (> 60%) was at elevations above 900 m. Based on our model, an estimated 56.1 km² of habitat exists in Puerto Rico with a high probability of occurrence. This total represents ~0.6% of the island's area. Public lands included 43.8% of habitat with high probability of occurrence (24.6 km²), 96% of which was located within four protected areas. Our results suggest that Sharp‐shinned Hawks are rare in Puerto Rico and restricted to the higher elevations of the Cordillera Central. Additional research is needed to identify and address ecological limiting factors, and recovery actions are needed to avoid the extinction of this endemic island raptor.     

Living on the edge: Multiscale habitat selection by cheetahs in a human‐wildlife landscape

Animals select habitats that will ultimately optimize their fitness through access to favorable resources, such as food, mates, and breeding sites. However, access to these resources may be limited by bottom‐up effects, such as availability, and top‐down effects, such as risk avoidance and competition, including that with humans. Competition between wildlife and people over resources, specifically over space, has played a significant role in the worldwide decrease in large carnivores. The goal of this study was to determine the habitat selection of cheetahs (Acinonyx jubatus) in a human‐wildlife landscape at multiple spatial scales. Cheetahs are a wide‐ranging, large carnivore, whose significant decline is largely attributed to habitat loss and fragmentation. It is believed that 77% of the global cheetah population ranges outside protected areas, yet little is known about cheetahs’ resource use in areas where they co‐occur with people. The selection, or avoidance, of three anthropogenic variables (human footprint density, distance to main roads and wildlife areas) and five environmental variables (open habitat, semiclosed habitat, edge density, patch density and slope), at multiple spatial scales, was determined by analyzing collar data from six cheetahs. Cheetahs selected variables at different scales; anthropogenic variables were selected at broader scales (720–1440 m) than environmental variables (90–180 m), suggesting that anthropogenic pressures affect habitat selection at a home‐range level, whilst environmental variables influence site‐level habitat selection. Cheetah presence was best explained by human presence, wildlife areas, semiclosed habitat, edge density and slope. Cheetahs showed avoidance for humans and steep slopes and selected for wildlife areas and areas with high proportions of semiclosed habitat and edge density. Understanding a species’ resource requirements, and how these might be affected by humans, is crucial for conservation. Using a multiscale approach, we provide new insights into the habitat selection of a large carnivore living in a human‐wildlife landscape.     

Fall migration and breeding origins of Canada Warblers moving through northern Colombia

Canada Warblers (Cardellina canadensis) are long‐distance Neotropical migrants, but little is known about their migratory behavior and ecology. We examined the fall migration of Canada Warblers at two sites, Darién and the Sierra Nevada de Santa Marta, in northern Colombia from 2011 to 2015 using constant‐effort mist‐netting. Our objectives were to determine: 1) breeding origins and connectivity patterns, 2) migratory pathways, 3) the phenology of migration, 4) possible differences in movements between ages and sexes, 5) their body condition when arriving in Colombia, and 6) evidence of stopover and refueling. Stable hydrogen isotopes (δ²H_f) in flight feathers were analyzed to estimate breeding origins of captured Canada Warblers in North America. The δ²H_f values revealed that most Canada Warblers captured in the Darién likely originated from the central and northeastern regions of their breeding range. The capture of all but one of 162 Canada Warblers in the Darién also indicates a migration route through Central American rather than across the Caribbean Sea. Most captured birds were hatch‐year birds (91% vs. 9% after hatch‐year birds), and we captured more females (67%) than males (33%). Canada Warblers migrated through the Darién from 20 September to early November, with most arriving in mid‐October. Most (89%) individuals arrived with low fuel reserves. These results combined with estimated flight ranges revealed that 46% of the individuals captured in the Darién likely needed to refuel to continue migrating, whereas 31% could continue 50 to 200 km beyond our capture site. However, no individuals were recaptured so stopover duration could not be determined. Canada Warblers may adopt a strategy of 1‐d stopovers and short flights or, alternatively, the Darién may represent low‐quality habitat and birds quickly left our study site in search of suitable habitat. Further study is needed to determine the possible importance of other (montane) habitats for Canada Warblers in the Darién region to prioritize conservation actions.     

Comparing Global Positioning System and Very High Frequency Telemetry Home Ranges of White-Tailed Deer

ABSTRACT Use of Global Positioning System (GPS) collars on free-ranging ungulates overcomes many limitations of conventional very high frequency (VHF) telemetry and offers a practical means of studying space use and home range estimation. To better understand winter home ranges of white-tailed deer (Odocoileus virginianus), we evaluated GPS collar performance, and we compared GPS- and VHF-derived diurnal home ranges (for the same animals) and GPS-derived home range estimates for diurnal and nocturnal locations. Overall, the mean fix success rate of our GPS collars was 85% (range = 14–99%). Kernel density estimates of home range (using the 95% probability contour) derived from GPS and VHF locations were generally similar, as were GPS-derived diurnal and nocturnal home ranges. Overlap indices between GPS and VHF utilization distributions (UDs) ranged from 0.49 to 0.78 for the volume of intersection (VI) index and from 0.67 to 0.94 for Bhattacharyya's affinity (BA); overlap indices for GPS-diurnal and nocturnal UDs ranged from 0.29 to 0.81 for VI and from 0.56 to 0.94 for BA. Despite similarities of home ranges estimated from GPS versus VHF locations and GPS-diurnal versus nocturnal locations, our data also indicate that differences may have important implications for studies focused on deer use of space, habitat, and resources at a finer scale.