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At least 307 records · Page 17Linked to original sources
USGS2008

Molt and aging criteria for four North American grassland passerines

Prairie and grassland habitats in central and western North America have declined substantially since settlement by Europeans (Knopf 1994) and many of the birds and other organisms that inhabit North American grasslands have experienced steep declines (Peterjohn and Sauer 1999; Johnson and Igl 1997; Sauer, Hines, and Fallon 2007). The species addressed here, Sprague’s Pipit (Anthus spragueii), Grasshopper (Ammodramus savannarum) and Baird’s (A. bairdii) sparrows, and Chestnut-collared Longspurs (Calcarius ornatus), are grassland birds that are of special conservation concern throughout their ranges due to declining populations and the loss of the specific grassland habitats required on both their breeding and wintering ranges (Knopf 1994, Davis and Sealy 1998, Davis 2003, Davis 2004, Jones and Dieni 2007). Population-trend data on grassland birds, while clearly showing declines, provides no information on the causes of population declines. Without demographic information (i.e., productivity and survivorship), there are no means to determine when in their life cycle the problems that are creating these declines are occurring, or to determine to what extent population trends are driven by factors that affect birth rates, death rates, or both (DeSante 1995). For migratory birds, population declines may be driven by factors on breeding grounds, during migration, and/or on wintering grounds. Lack of data on productivity and survivorship thus impedes the formulation of effective management and conservation strategies to reverse population declines (DeSante 1992). Furthermore, if deficiencies in survivorship are revealed, management strategies may need to address habitats on both breeding and non-breeding grounds, as well as along migratory pathways. One technique that helps inform management strategies is the biochemical analysis of isotopes and genetic markers, from the sampling of individual feathers from live birds (Smith et al. 2003, Pérez and Hobson 2006; Appendix). Determining demographic parameters and effectively sampling feathers to reveal connectivity between breeding and wintering grounds requires detailed knowledge of molt patterns and age determination criteria for the target species, in the hand. For example, productivity, survivorship, and territory acquisition may all be age-dependent, with first-year birds showing different patterns and responses than older birds. In many cases it may be possible to sample both a feather grown on the breeding grounds and one grown on the wintering grounds from a single individual, but knowledge of age-specific molt patterns, as well as an ability to recognize different feather generations, is needed to accomplish such a task. While some information on molt and aging criteria exists for grassland passerine species (Pyle 1997a), these species have been rarely captured during mark-recapture studies (Jones et al. 2007) and this information thus needs refining. There is a need for additional resources to assist field workers in determining molt patterns and age in captured individuals. Our objective is to describe molt and aging criteria for four grassland passerine species with the aid of digital photographs taken in the field. We hope that this document will be useful for researchers studying grassland species through capture and banding of live individuals on either the breeding or the wintering grounds. We present a general section on molt and aging techniques, followed by specific accounts for the four species treated: Sprague’s Pipits, Grasshopper and Baird sparrows, and Chestnut-collared Longspur. We also provide a brief protocol on collecting feather samples (Appendix).

Biological Technical Publication↗
USGS2025

Rallus elegans (King Rail) occupancy is stable, but habitat is in short supply in the Arkansas Delta

Secretive marsh birds experienced precipitous declines due to losses in wetland habitat across North America. However, from 1998 to 2004, wetland area increased, and between 2009 and 2019, the extent of emergent wetlands did not significantly decrease. This raises the question: how did secretive marsh birds, which are tied to emergent wetlands, respond to this period of relative stability in wetland area? Here, we use Rallus elegans (King Rail) occurrence data collected in 2005, 2006, 2012, and 2017 in the Arkansas Delta in the United States to test the hypothesis that a period of stability in wetland vegetation is linked to stable Rallus elegans occupancy. Specifically, we sought to (1) quantify relationships between R. elegans occupancy and land cover, (2) quantify temporal trends in R. elegans occupancy, and (3) characterize changes in land cover types linked to R. elegans occupancy. We developed spatial multi-season occupancy models, and our top model contained the categorical year effect but showed no trend in R. elegans occupancy between 2005 and 2017, instead showing high interannual variation in occupancy. We found strong associations between R. elegans occupancy and emergent wetlands (positive) and elevation (negative). From 2005 to 2017 in the ∼3.7 million ha Arkansas Delta, rice crop cover decreased by 294,750 ha, emergent wetlands increased by 6,719 ha, and all other cover types increased or decreased by < 7,500 ha. Thus, although emergent wetlands did increase, the total area of emergent wetlands in 2016 (22,262 ha) comprised <1% of the Arkansas Delta. Our results support the hypothesis that R. elegans occupancy stabilized during a time when the main habitat type R. elegans depend on, emergent wetlands, also stabilized in spatial extent. There is an opportunity to turn the tide in R. elegans declines by conserving extant emergent wetlands and creating new emergent wetlands.

Arkansas↗
USGS2014

Northern Pintail

This medium-sized dabbling duck of slender, elegant lines and conservative plumage coloration is circumpolar in distribution and abundant in North America, with core nesting habitat in Alaska and the Prairie Pothole Region of southern Canada and the northern Great Plains. Breeders favor shallow wetlands interspersed throughout prairie grasslands or arctic tundra. An early fall migrant, the species arrives on wintering areas beginning in August, after wing molt, often forming large roosting and feeding flocks on open, shallow wetlands and flooded agricultural fields. The birds consume grains, marsh plant seeds, and aquatic invertebrates throughout fall and winter. Northern Pintails are among the earliest nesting ducks in North America, beginning shortly after ice-out in many northern areas. Individuals form new pair bonds each winter but are highly promiscuous during the nesting season, with mated and unmated males often involved in vigorous, acrobatic Pursuit Flights. Annual nest success and productivity vary with water conditions, predation, and weather. Females build nests on the ground, often far from water. Only the female incubates; her mate leaves shortly after incubation begins. Ducklings hatch together in one day, follow the female to water after a day in the nest, and fledge by July or August. Adults and ducklings consume mainly aquatic invertebrates during the breeding season. Predators and farming operations destroy many thousands of Northern Pintail nests annually; farming has also greatly reduced the amount of quality nesting cover available. Winter habitats are threatened by water shortages, agricultural development, contamination, and urbanization. Periods of extended drought in prairie nesting regions have caused dramatic population declines, usually followed by periods of recovery. Over the long term, however, the continental population of Northern Pintails has declined significantly from 6 million birds in the early 1970s to less than 3 million in the late 1980s and early 1990s. Since then, the population appears to have stabilized; in 2013, the estimate was 3.3 million birds, a large number but below conservation goals despite favorable wetland conditions in much of the prairie breeding region. Ongoing conservation measures, however, such as habitat restoration and enhancement of agricultural lands, as well as prudent harvest management, suggest that Northern Pintails should have a secure future in North America.

The Birds of North America↗
USGS2016

Avian fatalities at wind energy facilities in North America: A comparison of recent approaches

Three recent publications have estimated the number of birds killed each year by wind energy facilities at 2012 build-out levels in the United States. The 3 publications differ in scope, methodology, and resulting estimates. We compare and contrast characteristics of the approaches used in the publications. In addition, we describe decisions made in obtaining the estimates that were produced. Despite variation in the 3 approaches, resulting estimates were reasonably similar; about a quarter- to a half-million birds are killed per year by colliding with wind turbines.

Human-Wildlife Interactions↗
USGS2024

Genotypic clustering of H5N1 avian Influenza viruses in North America evaluated by ordination analysis

The introduction of HPAI H5N1 clade 2.3.4.4b viruses to North America in late 2021 resulted in avian influenza outbreaks in poultry, mortality events in many wild bird species, and spillover into many mammalian species. Reassortment events with North American low pathogenic virus were identified as early as February 2022 and over 100 genotypes have been characterized. Such diversity increases the complexity and time required for monitoring virus evolution. Here, we performed ordination and clustering analyses on sequence data from H5N1 viruses identified in North America between January 2020 to December 2023 to visualize virus genotypic diversity in poultry and wildlife populations. Our results reveal that ordination and cluster-based approaches can complement traditional phylogenetic analyses specifically for the preliminary assignment of H5N1 viruses to genotypic groups or to identify novel genotypes. Our study expands current knowledge on genotype diversity of H5N1 viruses in North America and describes a rapid approach for early virus genotype assignment.

Viruses↗
USGS2007

Birds of the Rio Grande and other riparian habitats of Western Webb County, Texas

We conducted 164 diurnal morning point counts in 1997 and 89 nocturnal point counts in 1998 along the Rio Grande and at other riparian habitats on remote ranchland in northwestern Webb County. We subsequently conducted 94 diurnal morning and 37 nocturnal point counts in 1999 on public lands along the Rio Grande and at other riparian habitats at Laredo, Webb County. From these systematic surveys (n  384) and other irregular visits to sites during the length of the study, we detected a total of 209 bird species. Many species (97) are distributed widely over much of North America, but substantial numbers of species were also of primarily eastern (30), western (30), southwestern (26), and tropical (26) distributions. Fifty-five of the 209 species (26%) occur on >1 species priority lists in six bird conservation plans that we reviewed, but only four of these were tropical species. This suggests that tropical species, the driving force behind ecotourism-sustained economies in southern Texas, may not benefit directly from recent bird conservation plans, since their lists of priority species do not include many tropical birds. Thus, conservation projects designed to benefit primarily tropical species will not be ranked highly for funding if evaluated on the basis of the bird conservation plans we reviewed.

Bulletin of the Texas Ornithological Society↗
USGS1981

The North American Breeding Bird Survey

A brief history of the North American Breeding Bird Survey (BBS) and a discussion of the technique are presented. The approximately 2000 random roadside routes conducted yearly during the breeding season throughout North America produce an enormous bank of data on distribution and abundance of breeding birds with great potential use. Data on about one million total birds of 500 species per year are on computer tape to facilitate accessibility and are available to any serious investigator. The BBS includes the advantages of wide geographic coverage, sampling of most habitat types, standardization of data collection, and a relatively simple format. The Survey is limited by placement of roads (e.g., marshes and rugged mountainous areas are not well sampled), traffic noise interference in some cases and preference of some bird species for roadside habitats. These and other problems and biases of the BBS are discussed. The uniformity of the technique allows for detecting changes in populations and for creation of maps of relative abundance. Examples of each are presented.

Book chapter↗
USGS2018

Evaluating time-removal models for estimating availability of boreal birds during point count surveys: Sample size requirements and model complexity

We used conventional and finite mixture removal models with and without time-varying covariates to evaluate availability given presence for 152 bird species using data from point counts in boreal North America. We found that the choice of model had an impact on the estimability of unknown model parameters and affected the bias and variance of corrected counts. Finite mixture models provided better fit than conventional removal models and better adjusted for count duration. However, reliably estimating parameters and minimizing variance using mixture models required at least 200–1,000 detections. Mixture models with time-varying proportions of infrequent singers were best supported across species, indicating that accounting for date- and time-related heterogeneity is important when combining data across studies over large spatial scales, multiple sampling time frames, or variable survey protocols. Our flexible and continuous time-removal modeling framework can be used to account for such heterogeneity through the incorporation of easily obtainable covariates, such as methods, date, time, and location. Accounting for availability bias in bird surveys allows for better integration of disparate studies at large spatial scales and better adjustment of local, regional, and continental population size estimates.

Condor↗
USGS2024

Sero-epidemiology of Highly Pathogenic Avian Influenza viruses among wild birds in subarctic intercontinental transition zones

Background: The geographic expansion and evolution of A/Goose/Guangdong/1/1996(H5N1) (Gs/GD) lineage H5Nx highly pathogenic avian influenza (HPAI) viruses since 1996 have raised awareness of enzootic circulation among migratory birds and the potential for intercontinental transport and spread. Recent Pacific- and Atlantic-route introductions of HPAI to North America were facilitated by avian migration through subarctic zones, specifically Alaska and Iceland. This study aimed to identify recent historical patterns of exposure to HPAI viruses among birds within and migrating through both regions and evaluate how geographic, demographic, and taxonomic differences contribute to exposure risk at two intercontinental staging locations. Methods: During 2010-2019, blood samples were obtained from captured wild migratory seabirds and waterfowl in Alaska and Iceland. All live birds were released following completion of sampling. Sampling date, species, sampling location, and age class was documented for each bird, and sex was documented when possible. Lentiviral pseudoviruses that express the influenza hemagglutinin surface glycoprotein for H5Nx HPAI and H5 low-pathogenicity avian influenza (LPAI) were constructed for use in serological assays to screen for and quantify titers of antibodies against the latter viruses. Data were analyzed to compare (a) categorical baseline ecological traits between Iceland and Alaska, and (b) ecological traits between birds identified to be seropositive and suggestive/seronegative/fully cross-reactive birds to H5Nx HPAI in Iceland and Alaska. Factors associated with seroreactivity to H5Nx HPAI and H5 LPAI were assessed. Results: The seroprevalence of HPAI among birds in both locations was 7.3% (112/1526). Findings reveal variability in seroprevalence by year, higher rates of exposure to H5 LPAI than H5Nx HPAI overall, and significantly more seropositive and suggestive exposure of birds to H5Nx HPAI in Alaska as compared to Iceland. Geographic, demographic, and taxonomic differences contribute to exposure risk between Alaska and Iceland. Most tested birds were immuno-naïve to HPAI in both locations, which indicates many migratory birds in the subarctic are susceptible to HPAI infection, demonstrating substantial risk for intercontinental transmission between Asia, Europe, and North America. Conclusions: Our findings provide further justification for increased viral and serosurveillance in Alaska and Iceland to monitor subarctic movements of migratory birds and intercontinental transmission dynamics of currently circulating and new strains of HPAI globally.

Research Square↗
USGS1986

Winter distribution and oiling of common terns in Trinidad: A further look

Common Terns were studied during January and March 1985 in Trinidad as part of wintering terns in Latin America. Eighty-nine birds were captured, 33 in January, 56 in March. Terns averaged 102 .+-. 0.9 g, with March birds weighing more than those caught in January. This weight is similar to that reported earlier by Blokpoel et al. (1982, 1984) and is considerably less than weights of either premigratory immature or adult Common Terns. Terns in Trinidad appear to be opportunistic, using human fishing for their food source and roosting on boats, oil platforms and other man-made structures. One-half of the captured sample of birds had at least detectable amounts of oil on the plumage. This represents the highest frequency of oiling reported yet for any seabird living under 'baseline' (non-spill) conditions in North or Central America. Oiling had no apparent major effect on the condition of birds since oiled birds had similar weights and blood parameters when compared to unoiled birds.

Journal of Field Ornithology↗
USGS2021

Highly pathogenic avian influenza virus H5N2 (Clade 2.3.4.4) challenge of mallards age appropriate to the 2015 midwestern poultry outbreak

Background The 2015 highly pathogenic avian influenza virus (HPAIV) H5N2 clade 2.3.4.4 outbreak in upper midwestern U.S. poultry operations was not detected in wild birds to any great degree during the outbreak, despite wild waterfowl being implicated in the introduction, reassortment, and movement of the virus into North America from Asia. This outbreak led to the demise of over 50 million domestic birds and occurred mainly during the northward spring migration of adult avian populations. Objectives There have been no experimental examinations of the pathogenesis, transmission, and population impacts of this virus in adult wild waterfowl with varying exposure histories—the most relevant age class. Methods We captured, housed, and challenged adult wild mallards ( Anas platyrhynchos ) with HPAIV H5N2 clade 2.3.4.4 and measured viral infection, viral excretion, and transmission to other mallards. Results All inoculated birds became infected and excreted moderate amounts of virus, primarily orally, for up to 14 days. Cohoused, uninoculated birds also all became infected. Serological status had no effect on susceptibility. There were no obvious clinical signs of disease, and all birds survived to the end of the study (14 days). Conclusions Based on these results, adult mallards are viable hosts of HPAIV H5N2 regardless of prior exposure history and are capable of transporting the virus over short and long distances. These findings have implications for surveillance efforts. The capture and sampling of wild waterfowl in the spring, when most surveillance programs are not operating, are important to consider in the design of future HPAIV surveillance programs.

Wisconsin↗
USGS2003

Science for avian conservation: Priorities for the new millennium

Over the past decade, bird conservation activities have become the preeminent natural resource conservation effort in North America. Maturation of the North American Waterfowl Management Plan (NAWMP), establishment of Partners in Flight (PIF), and creation of comprehensive colonial waterbird and shorebird conservation plans have stimulated unprecedented interest in, and funding for, bird conservation in the United States, Canada, Mexico, and other countries in the western hemisphere. Key to that success in the United States has been active collaboration among federal, state and local governments, conservation organizations, academia, and industry. The U.S. Department of the Interior (DOI), which has primary statutory responsibility for migratory bird conservation and management, has been a key partner. Despite the great strides that have been made in bird conservation science, historical approaches to research and monitoring have often failed to provide sufficient information and understanding to effectively manage bird populations at large spatial scales. That shortcoming, and the lack of an integrated strategy and comprehensive set of research priorities, is more evident in light of the goals established by the North American Bird Conservation Initiative (NABCI). The NABCI is a trinational, coalition-driven effort to provide an organizational umbrella for existing conservation initiatives. The expanded focus of NABCI and individual bird conservation initiatives is to work together in an integrated, holistic fashion to keep common birds common and to increase populations of declining, threatened, and endangered species. To assist bird conservation initiatives in defining goals and developing new approaches to effective research, the U.S. Geological Survey (USGS), the research agency of DOI, convened a workshop, “Science for Avian Conservation: Understanding, Modeling, and Applying Ecological Relationships,” on 31 October–2 November 2000, which brought together 51 scientists from USGS, as well as scientists and conservationists from other agencies and organizations actively participating in NABCI. As the lead federal agency involved in bird conservation research, USGS has a clear legislative mandate to provide scientific information upon which future management plans and actions will be built. This article summarizes key issues and recommendations that arose from that workshop. The principal goal of the workshop was to guide USGS in defining its role, assessing capabilities, and directing future agency planning in support of bird conservation. A major component was to identify key areas of research needed in this new era of bird conservation science. Although tailored to the mission of USGS, workshop recommendations visualize a bold direction for future avian conservation science in which research and monitoring work in tandem with management to increase our understanding of avian populations and the processes that affect them. The USGS is a science agency whose role is to provide objective scientific information to management agencies and therefore is not directly involved in high-level resource policy-making or on-the-ground management decision making. Nevertheless, it is important to note that effective policy decision making must integrate the best available science with political and economic realities to achieve successful avian conservation—an important subject acknowledged in the workshop, but largely beyond its scope of discussion. Williams (2003) questions regarding how scientific information can be effectively communicated to decision makers and incorporated into natural resource policy. Without an aggressive vision and the willingness of researchers, managers, and policy makers to implement it, conservation of North American birds is likely to proceed without the full benefit of scientific investigation. These recommendations represent the principal conclusions drawn by workshop participants and do not necessarily reflect official USGS policy.

The Auk↗
USGS2015

Evidence for intercontinental parasite exchange through molecular detection and characterization of haematozoa in northern pintails ( Anas acuta ) sampled throughout the North Pacific Basin

Empirical evidence supports wild birds as playing a role in the interhemispheric exchange of bacteria and viruses; however, data supporting the redistribution of parasites among continents are limited. In this study, the hypothesis that migratory birds contribute to the redistribution of parasites between continents was tested by sampling northern pintails (Anas acuta) at locations throughout the North Pacific Basin in North America and East Asia for haemosporidian infections and assessing the genetic evidence for parasite exchange. Of 878 samples collected from birds in Alaska (USA), California (USA), and Hokkaido (Japan) during August 2011 - May 2012 and screened for parasitic infections using molecular techniques, Leucocytozoon, Haemoproteus, and Plasmodium parasites were detected in 555 (63%), 44 (5%), and 52 (6%) samples, respectively. Using an occupancy modeling approach, the probability of detecting parasites via replicate genetic tests was estimated to be high (p &ge; 0.95). Multi-model inference supported variation of Leucocytozoon parasite prevalence by northern pintail age class and geographic location of sampling in contrast to Haemoproteus and Plasmodium parasites for which there was only support for variation in parasite prevalence by sampling location. Thirty-one unique mitochondrial DNA haplotypes were detected among haematozoa infecting northern pintails including seven lineages shared between samples from North America and Japan. The finding of identical parasite haplotypes at widely distributed geographic locations and general lack of genetic structuring by continent in phylogenies for Leucocytozoon and Plasmodium provides evidence for intercontinental genetic exchange of haemosporidian parasites. Results suggest that migratory birds, including waterfowl, could therefore facilitate the introduction of avian malaria and other haemosporidia to novel hosts and spatially distant regions.

Alaska, California↗
USGS2009

Avian influenza at both ends of a migratory flyway: characterizing viral genomic diversity to optimize surveillance plans for North America

Although continental populations of avian influenza viruses are genetically distinct, transcontinental reassortment in low pathogenic avian influenza (LPAI) viruses has been detected in migratory birds. Thus, genomic analyses of LPAI viruses could serve as an approach to prioritize species and regions targeted by North American surveillance activities for foreign origin highly pathogenic avian influenza (HPAI). To assess the applicability of this approach, we conducted a phylogenetic and population genetic analysis of 68 viral genomes isolated from the northern pintail (Anas acuta) at opposite ends of the Pacific migratory flyway in North America. We found limited evidence for Asian LPAI lineages on wintering areas used by northern pintails in California in contrast to a higher frequency on breeding locales of Alaska. Our results indicate that the number of Asian LPAI lineages observed in Alaskan northern pintails, and the nucleotide composition of LPAI lineages, is not maintained through fall migration. Accordingly, our data indicate that surveillance of Pacific Flyway northern pintails to detect foreign avian influenza viruses would be most effective in Alaska. North American surveillance plans could be optimized through an analysis of LPAI genomics from species that demonstrate evolutionary linkages with European or Asian lineages and in regions that have overlapping migratory flyways with areas of HPAI outbreaks.

Alaska, California↗
USGS2011

Microanatomy of passerine hard-cornified tissues: Beak and claw structure of the black-capped chickadee (Poecile atricapillus)

The microanatomy of healthy beaks and claws in passerine birds has not been well described in the literature, despite the importance of these structures in avian life. Histological processing of hard‐cornified tissues is notoriously challenging and only a few reports on effective techniques have been published. An emerging epizootic of beak deformities among wild birds in Alaska and the Pacific Northwest region of North America recently highlighted the need for additional baseline information about avian hard‐cornified structures. In this study, we examine the beak and claw of the Black‐capped Chickadee ( Poecile atricapillus ), a common North American passerine that is affected by what has been described as “avian keratin disorder.” We use light and scanning electron microscopy and high‐magnification radiography to document the healthy microanatomy of these tissues and identify features of functional importance. We also describe detailed methods for histological processing of avian hard‐cornified structures and discuss the utility of special stains. Results from this study will assist in future research on the functional anatomy and pathology of hard‐cornified structures and will provide a necessary reference for ongoing investigations of avian keratin disorder in Black‐capped Chickadees and other wild passerine species.

Journal of Morphology↗
USGS2011

Which uncertainty? Using expert elicitation and expected value of information to design an adaptive program

Natural resource management is plagued with uncertainty of many kinds, but not all uncertainties are equally important to resolve. The promise of adaptive management is that learning in the short-term will improve management in the long-term; that promise is best kept if the focus of learning is on those uncertainties that most impede achievement of management objectives. In this context, an existing tool of decision analysis, the expected value of perfect information (EVPI), is particularly valuable in identifying the most important uncertainties. Expert elicitation can be used to develop preliminary predictions of management response under a series of hypotheses, as well as prior weights for those hypotheses, and the EVPI can be used to determine how much management could improve if uncertainty was resolved. These methods were applied to management of whooping cranes ( Grus americana ), an endangered migratory bird that is being reintroduced in several places in North America. The Eastern Migratory Population of whooping cranes had exhibited almost no successful reproduction through 2009. Several dozen hypotheses can be advanced to explain this failure, and many of them lead to very different management responses. An expert panel articulated the hypotheses, provided prior weights for them, developed potential management strategies, and made predictions about the response of the population to each strategy under each hypothesis. Multi-criteria decision analysis identified a preferred strategy in the face of uncertainty, and analysis of the expected value of information identified how informative each strategy could be. These results provide the foundation for design of an adaptive management program.

Biological Conservation↗
USGS2023

Ferruginous Hawk movements respond predictably to intra-annual variation but unexpectedly to anthropogenic habitats

Birds exhibit flexible movement responses to environmental variation across the annual cycle, and those responses can provide insight into potential impacts that environmental changes may have on these species. To understand year-round variation in space use by Ferruginous Hawks Buteo regalis , we tracked 12 birds breeding in southwestern Idaho, USA, using GPS telemetry collected over 207 bird-months. Home-range sizes of territorial adult hawks showed strong intra-annual variation, being smallest from April to June and largest from July to October. In contrast, juvenile birds (< 2 years old) did not appear to hold territories and showed no detectable intra-annual variation in ranging behaviour. Association with land-cover types by territorial birds varied between breeding and non-breeding months and was linked to home-range size. Home-range sizes of non-territorial birds were larger than those of territorial birds, and that size did not vary across the year. Association with anthropogenic habitats (irrigated cropland habitats that can provide high rodent densities and increased foraging opportunities) was negatively associated with home-range size in months of the non-breeding season. Unexpectedly, the opposite was true in the months of the breeding season, such that use of croplands resulted in larger home-ranges. Patterns in home-range size were probably linked to intrinsic factors such as the timing of breeding and migratory behaviour, and to extrinsic factors such as prey availability associated with specific land-cover types. These results have implications for our understanding of the response of Ferruginous Hawks and other similar species to predicted changes in land cover, and they suggest unexpected relationships between human activity and wildlife behaviour. Furthermore, because the birds we tracked used a large portion of western North America, they are probably relevant far beyond the small area where these individuals were trapped.

Idaho↗
USGS2024

Monthly variation in home range of a steppe-dwelling raptor

Birds in steppe landscapes change their behaviour over the annual cycle. We used GPS telemetry to track 12 steppe-dwelling adult Ferruginous Hawks ( Buteo regalis ) to understand how their home ranges varied across the year. Home range sizes of territorial adult hawks showed strong intra-annual variation, being smallest from April to June, and largest from July to October. Patterns in home range size were likely linked to intrinsic factors such as the timing of breeding and migratory behaviour, and to extrinsic factors such as prey availability associated with specific landcover types. These results have implications for our understanding of the response of steppe birds to predicted changes in land cover, and they suggest potential relationships between human activity and wildlife behaviour. Because the birds we tracked used a large portion of western North America, they are likely relevant far beyond the small area where these individuals were trapped.

Conference Paper↗