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At least 1,117 records · Page 62Linked to original sources
USGS2002

Regional fidelity and movement patterns of wintering killdeer in an agricultural landscape

Killdeer ( Charadrius vociferus ) is a common and widespread North American species for which there are few studies of residency patterns and movements. We quantified fidelity and movement patterns of 24 radio-tagged Killdeer in the Willamette Valley of Oregon during the winter of 1999-2000. Results from telemetry surveys and census efforts revealed that the group monitored was composed of winter residents (63%), winter transients (26%), and year-round residents (11%). Movements were localized with birds detected at an average distance of 5.15 ± 0.91 (SE) km from the site of capture. Mean home range size (95% kernel) was 7.73 ± 3.19 km 2 . However, results also indicated periodic exploratory movements, with some birds detected up to 30 km from marking sites. Overall, individuals exhibited a low degree of fidelity to specific sites and were detected at an average of 11.9 ± 1.1 sites. No differences were found in monthly movement patterns. In almost all cases, year-round residents were more sedentary than winter residents and winter transients. Results indicate a complex regional population structure and highlight the need to consider both migrant and resident birds, as well as seasonal differences in habitat needs and space use requirements, in future conservation planning efforts.

Oregon↗
USGS2010

Calibrating recruitment estimates for mourning doves from harvest age ratios

We examined results from the first national-scale effort to estimate mourning dove ( Zenaida macroura ) age ratios and developed a simple, efficient, and generalizable methodology for calibrating estimates. Our method predicted age classes of unknown-age wings based on backward projection of molt distributions from fall harvest collections to preseason banding. We estimated 1) the proportion of late-molt individuals in each age class, and 2) the molt rates of juvenile and adult birds. Monte Carlo simulations demonstrated our estimator was minimally biased. We estimated model parameters using 96,811 wings collected from hunters and 42,189 birds banded during preseason from 68 collection blocks in 22 states during the 2005–2007 hunting seasons. We also used estimates to derive a correction factor, based on latitude and longitude of samples, which can be applied to future surveys. We estimated differential vulnerability of age classes to harvest using data from banded birds and applied that to harvest age ratios to estimate population age ratios. Average, uncorrected age ratio of known-age wings for states that allow hunting was 2.25 (SD 0.85) juveniles:adult, and average, corrected ratio was 1.91 (SD 0.68), as determined from harvest age ratios from an independent sample of 41,084 wings collected from random hunters in 2007 and 2008. We used an independent estimate of differential vulnerability to adjust corrected harvest age ratios and estimated the average population age ratio as 1.45 (SD 0.52), a direct measure of recruitment rates. Average annual recruitment rates were highest east of the Mississippi River and in the northwestern United States, with lower rates between. Our results demonstrate a robust methodology for calibrating recruitment estimates for mourning doves and represent the first large-scale estimates of recruitment for the species. Our methods can be used by managers to correct future harvest survey data to generate recruitment estimates for use in formulating harvest management strategies.

Journal of Wildlife Management↗
USGS1956

Ecological study of ruffed grouse broods in Virginia

The Ruffed Grouse ( Bonasa umbellus ), commonly called "pheasant" throughout the southern Appalachian region, is a popular game bird in the mountains of Virginia. Unfortunately, however, the grouse populations in this State have declined noticeably during the past fifty years. Because of this, special field studies were designed through the cooperation of the U. S. Fish and Wildlife Service and U. S. Forest Service, which would provide information that could be used in devising more efficient grouse management practices. As part of this program, I was assigned to investigate the ecology and habits of this species in the Shenandoah Mountains during the spring and summer of 1941. These studies were conducted within the George Washington National Forest in northwestern Augusta County, southwestern Rockingham County, and northeastern Highland County, Virginia.

The Auk↗
USGS2015

Changing arctic ecosystems—What is causing the rapid increase of snow geese in northern Alaska?

Through the Changing Arctic Ecosystems (CAE) initiative, the U.S. Geological Survey (USGS) informs key resource management decisions for Arctic Alaska by providing scientific information on current and future ecosystem response to a warming climate. The Arctic Coastal Plain (ACP) of northern Alaska is a key study area within the USGS CAE initiative. This region has experienced a warming trend over the past decades, leading to decreased sea ice, permafrost thaw, and an advancement of spring phenology. The number of birds on the ACP also is changing, marked by increased populations of the four species of geese that nest in the region. The Snow Goose ( Chen caerulescens ) is the most rapidly increasing of these species. USGS CAE research is quantifying these changes and their implications for management agencies.

Alaska↗
USGS1995

Colonial waterbirds

Colonial waterbirds, that is, seabirds (gulls, terns, cormorants, pelicans) and wading birds (herons, egrets, ibises), have attracted the attention of scientists, conservationists, and the public since the turn of the century when plume hunters nearly drove many species to extinction. The first national wildlife refuge at Pelican Island, Florida, was founded to conserve a large nesting colony of the brown pelican ( Pelecanus occidentalis ). The National Audubon Society also established a game warden system to monitor and protect important waterbird colonies. These efforts helped establish federal laws to protect migratory birds and their nesting habitats in North America. Although the populations of many species rebounded in the early part of the 20th century, major losses and alteration of coastal wetlands still threaten the long-term sustainability of many colonial waterbirds. A national, coordinated monitoring program is needed to monitor population status and trends in colonial waterbirds (Erwin et al. 1993). The Canadian Wildlife Service has recently established a national seabird monitoring program (D. Nettleship, CWS, personal communication). In addition, better coordination and cooperation for monitoring waterbirds are needed on both their breeding grounds in North America and their wintering grounds in Latin America where wetland loss is also a critical problem (Erwin et al. 1993). This article summarizes the status and trends of selected waterbird species in North America, but excludes Alaska, Hawaii, and the Pacific coast, which are described elsewhere.

Book chapter↗
USGS1971

Some patterns of woodcock activities on Maine summer fields

Certain aspects of woodcock usage of summer fields were studied in Maine. Findings were as follows: ....1. On two study fields in 1968, numbers of woodcock first began spending nights in the fields during the second week of June. During 1968 and 1969, the number of birds flushed from the fields varied greatly between nights. Use of fields continued into the first week of November......2. Woodcock started flying into summer fields approximately 26 minutes after sunset. Unless disturbed, birds remained on fields throughout the night and started departing for diurnal covers about 48 minutes before sunrise. The duration of evening and morning flight periods averaged 13 to 15 minutes.....3. Woodcock did not necessarily use the same field throughout the summer. Five of the 36 birds taken as repeats were caught on fields other than where originally banded. However, it was believed that flights to and from fields were essentially local movements.....4. Vegetation appeared to have been a critical factor influencing the distribution of woodcock in fields. Areas of low ground cover interspersed with taller and denser cover were used most frequently.....5. Immatures, especially immature males, were the predominant age-sex class captured on Maine summer fields. The question of whether the age-sex composition of birds using summer fields is atypical of the total woodcock population requires additional study.

The Wilson Bulletin↗
USGS2007

Laysan Teal Anas laysanensis nesting phenology and site characteristics on Laysan Island

Factors influencing breeding initiation of the endangered Laysan Teal Anas laysanensis were studied on Laysan Island in the Hawaiian Islands National Wildlife Refuge between 1998 and 2006. Sixty-two radio-tagged adult females were tracked for 30-180 days to locate and describe their nest sites. In addition, the Laysan Teal were surveyed daily during the breeding season, and 331 individually colour-ringed females were marked to identify new broods and timing of incubation initiation. Temperature, rainfall, and abundance of Brine Flies (Scatella sexnotata, an important prey) were measured in all years. Females nested on average 213 m (s.e. ?? 37 m) from the lake basin primarily in Eragrostis variablis, a native bunch grass with > 75% cover. The first observation of nesting in marine debris by Laysan Teal was reported. The initiation of incubation, at the start of the breeding season each year, varied from December to July, and differed significantly between years. Brine Fly abundance, temperature, and rainfall also varied significantly between years. The earlier the Brine Fly abundance peaked, the longer the duration of the breeding season. The length of the breeding season, measured as the number of days between the first and last clutches, varied from 83-192 days (mean 116 ?? 14 days). Annual brood production was positively correlated with spring peak abundance of Brine Flies. There was some evidence that it was negatively correlated with the number of adult females in the population. Rainfall, temperature, prey abundance, and the density of other birds on Laysan Island are likely to interact in influencing Laysan Teal's variable nesting phenology and productivity. ?? Wildfowl & Wetlands Trust.

Wildfowl↗
USGS2010

Status and conservation of parrots and parakeets in the Greater Antilles, Bahama Islands, and Cayman Islands

In the 1490S a minimum of 28 species of psittacines occurred in the West Indies. Today, only 43% (12) of the species survive. All macaws and most parakeet species have been lost. Although the surviving parrot fauna of the Greater Antilles, Cayman Islands, and Bahama Islands has fared somewhat better than that of the Lesser Antilles, every species has undergone extensive reductions of populations and all but two have undergone extensive reductions in range, mostly as a result of habitat loss, but also from persecution as agricultural pests, conflicts with exotic species, harvesting for pets, and natural disasters. The Cayman Brae Parrot Amazona leucocephala hesterna , with its tiny population (lessthan 150 individuals in the wild) and range, and the Puerto Rican Parrot A. vittata , with 22-23 birds in the wild and 56 individuals in captivity, must be considered on the of extinction and in need of (in the tatter's case, continuing) aggressive programmes of research and management. Other populations declining in numbers and range include the Yellow-billed Amazona collaria , and Black-billed A. agilis Parrots of Jamaica, Hispaniolan Parakeet Aratinga chloroptera , Hispaniolan Parrot Amazona ventralis , Cuban Parrot A. leucocephala leucocephala and, most seriously, Cuban Parakeet Aratinga euops . The population of the Grand Cayman Parrot ( Amazona leucocephala caymanensis ), although numbering only about 1,000 birds, appears stable and the current conservation programme gives hope for the survival of the race. An active conservation and public education programme has begun for the Bahama Parrot A. l. bahamensis , which still occurs in good numbers on Great Inagua Island, but is threatened on Abaco Island. Recommendations for conservation of parrots and parakeets in the region include (1) instituting term programmes of research to determine distribution, status, and ecology of each species; (2) developing conservation programmes through education and management approaches that are culturally, politically, and economically sensitive to the region; and providing and protecting habitat within suitably sized reserves.

Bird Conservation International↗
USGS2005

Hierarchical models and Bayesian analysis of bird survey information

Summary of bird survey information is a critical component of conservation activities, but often our summaries rely on statistical methods that do not accommodate the limitations of the information. Prioritization of species requires ranking and analysis of species by magnitude of population trend, but often magnitude of trend is a misleading measure of actual decline when trend is poorly estimated. Aggregation of population information among regions is also complicated by varying quality of estimates among regions. Hierarchical models provide a reasonable means of accommodating concerns about aggregation and ranking of quantities of varying precision. In these models the need to consider multiple scales is accommodated by placing distributional assumptions on collections of parameters. For collections of species trends, this allows probability statements to be made about the collections of species-specific parameters, rather than about the estimates. We define and illustrate hierarchical models for two commonly encountered situations in bird conservation: (1) Estimating attributes of collections of species estimates, including ranking of trends, estimating number of species with increasing populations, and assessing population stability with regard to predefined trend magnitudes; and (2) estimation of regional population change, aggregating information from bird surveys over strata. User-friendly computer software makes hierarchical models readily accessible to scientists.

Book chapter↗
USGS1992

Ecology of playa lakes

Between 25,000 and 30,000 playa lakes are in the playa lakes region of the southern high plains (Fig. 1). Most playas are in west Texas (about 20,000), and fewer, in New Mexico, Oklahoma, Kansas, and Colorado. The playa lakes region is one of the most intensively cultivated areas of North America. Dominant crops range from cotton in southern areas to cereal grains in the north. Therefore, most of the native short-grass prairie is gone, replaced by crops and, recently, grasses of the Conservation Reserve Program. Playas are the predominant wetlands and major wildlife habitat of the region. More than 115 bird species, including 20 species of waterfowl, and 10 mammal species have been documented in playas. Waterfowl nest in the area, producing up to 250,000 ducklings in wetter years. Dominant breeding and nesting species are mallards and blue-winged teals. During the very protracted breeding season, birds hatch from April through August. Several million shorebirds and waterfowl migrate through the area each spring and fall. More than 400,000 sandhill cranes migrate through and winter in the region, concentrating primarily on the larger saline lakes in the southern portion of the playa lakes region. The primary importance of the playa lakes region to waterfowl is as a wintering area. Wintering waterfowl populations in the playa lakes region range from 1 to 3 million birds, depending on fall precipitation patterns that determine the number of flooded playas. The most common wintering ducks are mallards, northern pintails, green-winged teals, and American wigeons. About 500,000 Canada geese and 100,000 lesser snow geese winter in the playa lakes region, and numbers of geese have increased annually since the early 1980’s. This chapter describes the physiography and ecology of playa lakes and their attributes that benefit waterfowl.

Fish and Wildlife Leaflet↗
USGS2025

Developing research tools for demographic study of Rhynchophanes mccownii (thick-billed longspurs)

Like numerous other North American grassland bird species, Rhynchophanes mccownii (thick-billed longspur) has experienced severe population declines in the last 50 years. Little is known about population-limiting factors, and knowledge gaps limit conservation efforts on the species; however, before research studies aimed at improving conservation and management actions can be developed, other research must resolve notable knowledge gaps that exist in field techniques for efficient and effective large-scale demographic studies. We examined several techniques for the capture, marking (metal, color bands, and transmitters), and reencountering (resights and telemetry) of thick-billed longspurs in croplands and prairies in Valley County, Montana, during the 2022 and 2023 breeding seasons. Our goal was to evaluate the feasibility of obtaining within- and between-season resights of individual thick-billed longspurs using optical equipment and cameras, transmitter receivers, and the Motus automatic receiving station network. This report includes observations and insights that may aid researchers embarking on future demographic studies of thick-billed longspurs, as well as other grassland birds that provide similar research challenges.

Open-File Report↗
USGS2004

Multi-state analysis of the impacts of avian pox on a population of Serins (Serinus serinus): The importance of estimating recapture rates

Disease is one of the evolutionary forces shaping populations. Recent studies have shown that epidemics like avian pox, malaria, or mycoplasmosis have affected passerine population dynamics, being responsible for the decline of some populations or disproportionately killing males and larger individuals and thus selecting for specific morphotypes. However, few studies have estimated the effects of an epidemic by following individual birds using the capture-recapture approach. Because avian pox can be diagnosed by direct examination of the birds, we are here able to analyze, using multistate models, the development and consequences of an avian pox epidemic affecting in 1996, a population of Serins (Serinus serinus) in northeastern Spain. The epidemics lasted from June to the end of November of 1996, with a maximum apparent prevalence rate > 30% in October. However, recapture rate of sick birds was very high (0.81, range 0.37-0.93) compared to that of healthy birds (0.21, range 0.020-32), which highly inflated apparent prevalence rate. This was additionally supported by the low predicted transition from the state of being uninfected to the state of being infected (0.03, SE 0.03). Once infected, Serin avian pox was very virulent with (15-day) survival rate of infected birds being of only 0.46 (SE 0.17) compared to that of healthy ones (0.87, SE 0.03). Probability of recovery from disease, provided that the bird survived the first two weeks, however, was very high (0.65, SE 0.25). The use of these estimates together with a simple model, allowed us to predict an asymptotic increase to prevalence of about 4% by the end of the outbreak period, followed by a sharp decline, with the only remaining infestations being infected birds that had not yet recovered. This is in contrast to the apparent prevalence of pox and stresses the need to estimate recapture rates when estimating population dynamics parameters. ?? 2004 Museu de Cie??ncies Naturals.

Animal Biodiversity and Conservation↗
USGS1983

Effects of oil on avian reproduction: A review and discussion

Oil pollution is a highly visible form of environmental contamination that affects avian reproduction in a variety of ways. Plumage oiling causes widespread and locally severe mortality of adult birds. Egg oiling can be a serious hazard for bird embryos but only a few field observationons of this have been reported. Oil ingestion seldom kills birds directly but it causes sublethal change~ in the bodily functions and behavior of adults and nestlings. Studies of the effects of oil on avian reproduction have produced varied and, in ingestion studies, sometimes conflicting results because of inconsistent experimental design and the use of different test species and types of oil. Field experimentation with the sublethal effects of ingested oil on avian reproduction has been limited. Simulation modelling of seabird populations has shown that (l) an occasional decrease in survival of breeding adults will have a greater impact on seabird populations than an occasional decrease in reproductive success, and (2) populations of long-lived seabirds with low reproductive potential have great difficulty recovering from high one-time mortality when experiencing even small sustained annual decreases in either natality or breeding adult survival. The impact of oil-related decreases in survival or reproduction will be more noticeable at the local or colony level than at the regional or species level. Immigration, surplus breeders, and possible compensatory changes in natality and mortality resulting from population reductions usually prevent local population reductions from lasting very long (unless the species is rare or at the edge of its range). A study of west European seabird populations indicates that the natural annual mortality of the region greatly exceeds the annual mortality due to plumage oiling; effects of oil ingestion and egg oiling were not measured but were thought to be less than the mortality from plu~age oiling. Oil-related mortality, even if in addition to expected mortality, would not have a detectable impact on regional populations if environmental conditions were favorable (increased natality, decreased mortality) for the birds.

Book chapter↗
USGS1992

Application of a computer simulation model to migrating white-fronted geese in the Klamath Basin

The Pacific greater white-fronted goose ( Anser albifrons ) population has declined precipitously over the past 20 years. Loss of wetland habitat in California wintering areas has had a significant effect on the population, so recovery of the population may depend on innovative management of the few remaining wetlands. A computer simulation model, REFMOD, was applied to greater white-fronted geese in the Klamath Basin, northern California, to investigate the importance of food availability and hunting disturbance to migrating and wintering populations. Time spent flying and feeding was simulated during fall and early winter, and the resulting energy expenditure was compared with energy consumed to calculate an overall energy balance. This energy balance and the ease with which waterfowl acquired needed food affected emigration rate, and thus, the waterfowl population level was directly tied to availability and distribution of food. The model validly described distances moved by geese from their Tule Lake Refuge roosting site (core) to feeding sites within the surrounding Klamath Basin arena, and exhibited a capability to simulate observed time spent feeding. Based on 25 stochastic simulations, greater white-fronted goose population dynamics were validly simulated over the fall and early-winter (P>0.8). When food was removed from the Tule Lake Refuge, simulated geese had to fly farther (P<0.0001) to find food, hastening emigration and resulting in a decline (P<0.05) in use of the Klamath Basin by geese. Although barley is normally abundant in the basin and is extensively used by geese, simulated elimination of barley in the arena did not cause a reduction in goose numbers (P>0.05). The elimination did cause an increase in the distance traveled to feed (P<0.05), but the availability of other foods in the basin (e.g., potatoes) was evidently sufficient to support the population. The elimination of hunting in the Klamath Basin, and the related decrease in disturbance of feeding birds, had little effect (P>0.05) on the distance traveled to feed or on goose numbers. A 10-fold increase in disturbance hastened emigration and reduced population levels (P<0.0001) during the season by about 30%; a 100-fold increase in disturbance reduced population levels (P<0.0001) by 85%. When goose immigration was increased to simulate an average peak population of approximately 500 000 geese, population levels remained high throughout the fall, indicating the Klamath Basin can sustain a population much larger than currently exists. This suggests food availability and disturbance levels in the Klamath Basin are not responsible for observed population declines during the last 2 decades. REFMOD can easily be used to evaluate the effects of other scenarios related to hunting regimes and food distribution and availability.

Book chapter↗
USGS1991

Growth and development of thermoregulation in nestling San Miguel Island Song Sparrows

Patterns of growth (reviewed by Ricklefs 1968, 1969; O'Connor 1984) and the development of endothermy (reviewed by Dawson and Hudson 1970, Dunn 1975, Hill and Beaver 1982) have been well-studied in altricial wild birds, especially passerines. But few studies compare grown and thermogenesis in separate populations of the same species. Results of such studies with emberizids varied among species. King and Hubbard (1981), for example, found that nestlings from subarctic, subalpine, and low-altitude montane populations of White-crowned Sparrows ( Zonotrichia leucophrys gambelii ) grew at similar rates. In contrast, Rogers (1985) reported that the growth rates of nestlings in different populations of Savannah Sparrows ( Passerculus sandwichensis ) varied in response to the different environmental constraints of the localities in which they were reared. Nice (1937) and Smith et al. (1982) documented patterns of nestling growth in mainland (Ohio) and insular (Mandarte Island, British Columbia, Canada) populations of Song Sparrows ( Melospiza melodia ), respectively, and found that they were similar to those reported for most other passerines by Ricklefs (1968, 1969) and O'Connor (1984). In 1985-1986, we had the opportunity to examine the growth of nestlings from a third race of Song Sparrows, M. m. micronyx , which is endemic to San Miguel Island near Santa Barbara, California. We also studied the development of endothermy in these young birds, a process not hitherto described for nestling Song Sparrows. We report both in this paper.

California↗
USGS2017

Mechanisms associated with an advance in the timing of seasonal reproduction in an urban songbird

The colonization of urban environments by animals is often accompanied by earlier breeding and associated changes in seasonal schedules. Accelerated timing of seasonal reproduction in derived urban populations is a potential cause of evolutionary divergence from ancestral populations if differences in physiological processes that regulate reproductive timing become fixed over time. We compared reproductive development in free-living and captive male dark-eyed juncos deriving from a population that recently colonized a city (~35 years) and ceased migrating to that of conspecifics that live in sympatry with the urban population during winter and spring but migrate elsewhere to breed. We predicted that the earlier breeding sedentary urban birds would exhibit accelerated reproductive development in the spring along the hypothalamic-pituitary-gonadal (HPG) axis as compared to migrants. We found that free-living sedentary urban and migrant juncos differed at the level of the pituitary when measured as baseline luteinizing hormone (LH) levels, but not in increased LH when challenged with Gonadotropin-Releasing Hormone (GnRH). Among captives held in a common garden, and at the level of the gonad, we found that sedentary urban birds produced more testosterone in response to GnRH than migrants living in the same common environment, suggesting greater gonadal sensitivity in the derived urban population. Greater gonadal sensitivity could arise from greater upstream activation by LH or FSH or from reduced suppression of gonadal development by the adrenal axis. We compared abundance of gonadal transcripts for LH receptor (LHR), follicle stimulating hormone receptor (FSHR), glucocorticoid receptor (GR), and mineralocorticoid receptor (MR) in the common-garden, predicting either more abundant transcripts for LHR and FSHR or fewer transcripts for GR and MR in the earlier breeding sedentary urban breeders, as compared to the migrants. We found no difference in the expression of these genes. Together these data suggest that advanced timing of reproduction in a recently derived urban population is facilitated by earlier increase in upstream baseline activity of the HPG and earlier release from gonadal suppression by yet-to-be-discovered mechanisms. Evolutionarily, our results suggest that potential for gene flow between seasonally sympatric populations may be limited due to urban-induced advances in the timing of reproduction and resulting allochrony with ancestral forms.

California↗
USGS2010

Population structure and genetic diversity of greater sage-grouse (Centrocercus urophasianus) in fragmented landscapes at the northern edge of their range

Range-edge dynamics and anthropogenic fragmentation are expected to impact patterns of genetic diversity, and understanding the influence of both factors is important for effective conservation of threatened wildlife species. To examine these factors, we sampled greater sage-grouse ( Centrocercus urophasianus ) from a declining, fragmented region at the northern periphery of the species’ range and from a stable, contiguous core region. We genotyped 2,519 individuals at 13 microsatellite loci from 104 leks in Alberta, Saskatchewan, Montana, and Wyoming. Birds from northern Montana, Alberta, and Saskatchewan were identified as a single population that exhibited significant isolation by distance, with the Milk River demarcating two subpopulations. Both subpopulations exhibited high genetic diversity with no evidence that peripheral regions were genetically depauperate or highly structured. However, river valleys and a large agricultural region were significant barriers to dispersal. Leks were also composed primarily of non-kin, rejecting the idea that leks form because of male kin association. Northern Montana sage-grouse are maintaining genetic connectivity in fragmented and northern peripheral habitats via dispersal through and around various forms of fragmentation.

Alberta, Saskatchewan, Montana, Wyoming↗
USGS2008

Distribution and behaviour of passerines around Peregrine Falco peregrinus eyries in western Greenland

This paper describes the distribution and behaviour of passerine birds within 1 km of Peregrine Falcon Falco peregrinus eyries in western Greenland. Passerine populations were censused in 1983 around six cliffs occupied by nesting Peregrines and at six sites on the open tundra, and in 1984 at two unoccupied sites suitable for Peregrine nesting. Four passerine species accounted for over 90% of birds seen. Within 400 m of Peregrine occupied cliffs, three species, Lapland Longspur Calcarius lapponicus . Northern Wheatear Oenanthe oenanthe , and Common Redpoll Carduelisflammea , were found in lower than average abundance while the fourth, Snow Bunting Plectrophenax nivalis , was found in increased abundance. Our indirect tests suggest that Peregrine presence, rather than direct predation, was responsible for the distributions of the first three species. The Snow Bunting, however, behaviourally adapts to Peregrine presence in order to exploit nesting habitat available at the cliff base. These results contrast strongly with those reported by other Arctic workers, where increased abundances of potential prey were observed in close proximity to nesting Peregrines.

Ibis↗