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At least 541 records · Page 30Linked to original sources
USGS2024

Predator disturbance contributed to Common Murre Uria aalge breeding failures in Cook Inlet, Alaska following the 2014–2016 Pacific marine heatwave

The 2014-2016 Pacific marine heatwave caused unprecedented die-offs and multi-year reproductive failures for Common Murres Uria aalge along the west coast of North America. Lingering impacts, such as declines in colony attendance and productivity, have persisted at some colonies following the heatwave and are attributed largely to changes in prey availability and quality. Here, we present evidence of an additional, top-down mechanism contributing to Common Murre breeding failures on Gull Island (Alaska): disturbance of nesting birds by aerial predators and associated egg depredation. We collected time-lapse images over five murre breeding seasons (2016-2020) on Gull Island to document the frequency, duration, and intensity of disturbances caused by aerial predators, as well as to quantify disturbance-associated egg depredation. To identify seasonal and inter-annual variability of disturbances, we calculated a daily disturbance index and compared years using generalized additive models. In all years, Bald Eagles Haliaeetus leucocephalus were the primary cause of disturbance, which led to periods of prolonged colony abandonment by murres and facilitated high levels of murre egg depredation by Glaucous-winged Gulls Larus glaucescens and Herring Gulls L. argentatus . We found that the seasonality of disturbance was an important factor in determining egg depredation rates. In years when disturbance levels were high and persisted later in the season, the colony experienced complete breeding failures due to disturbance-associated egg depredation. Our study revealed that the response of nesting murres to a strong environmental perturbation, such as the Pacific marine heatwave, can be complex and involve multiple stressors from both bottom-up and top-down factors.

Alaska↗
USGS2017

Intraspecific evolutionary relationships among peregrine falcons in western North American high latitudes

Subspecies relationships within the peregrine falcon ( Falco peregrinus ) have been long debated because of the polytypic nature of melanin-based plumage characteristics used in subspecies designations and potential differentiation of local subpopulations due to philopatry. In North America, understanding the evolutionary relationships among subspecies may have been further complicated by the introduction of captive bred peregrines originating from non-native stock, as part of recovery efforts associated with mid 20 th century population declines resulting from organochloride pollution. Alaska hosts all three nominal subspecies of North American peregrine falcons– F . p . tundrius , anatum , and pealei –for which distributions in Alaska are broadly associated with nesting locales within Arctic, boreal, and south coastal maritime habitats, respectively. Unlike elsewhere, populations of peregrine falcon in Alaska were not augmented by captive-bred birds during the late 20 th century recovery efforts. Population genetic differentiation analyses of peregrine populations in Alaska, based on sequence data from the mitochondrial DNA control region and fragment data from microsatellite loci, failed to uncover genetic distinction between populations of peregrines occupying Arctic and boreal Alaskan locales. However, the maritime subspecies, pealei , was genetically differentiated from Arctic and boreal populations, and substructured into eastern and western populations. Levels of interpopulational gene flow between anatum and tundrius were generally higher than between pealei and either anatum or tundrius . Estimates based on both marker types revealed gene flow between augmented Canadian populations and unaugmented Alaskan populations. While we make no attempt at formal taxonomic revision, our data suggest that peregrine falcons occupying habitats in Alaska and the North Pacific coast of North America belong to two distinct regional groupings–a coastal grouping ( pealei ) and a boreal/Arctic grouping (currently anatum and tundrius )–each comprised of discrete populations that are variously intra-regionally connected.

Alaska↗
USGS2013

Estimating transmission of avian influenza in wild birds from incomplete epizootic data: implications for surveillance and disease spreac

Estimating disease transmission in wildlife populations is critical to understand host–pathogen dynamics, predict disease risks and prioritize surveillance activities. However, obtaining reliable estimates for free-ranging populations is extremely challenging. In particular, disease surveillance programs may routinely miss the onset or end of epizootics and peak prevalence, limiting the ability to evaluate infectious processes. We used profile likelihood to estimate the force of infection (FOI) in a low pathogenic avian influenza virus (LPAIv) epizootic model from censored time series of LPAIv prevalence in hatch-year waterfowl (order Anseriformes) at postbreeding and migration sites in North America. We found a mean LPAIv FOI of 0·12 day −1 [95% CI, 0·00–0·39], corresponding to an incidence rate of 0·11 day −1 , with geographic heterogeneity (min–max: 0·02–0·23 day −1 ) among study sites. These high infection rates indicate that most hatch-year waterfowl are likely infected with LPAIv early in the fall migration. Comparison of model-predicted and observed immunity confirmed our assumption of naïve hatch-year waterfowl and suggested long-term immunity (>6 months) for adults. Using the mean LPAIv incidence rate, we predict a shorter and lower epizootic curve for highly pathogenic avian influenza virus (HPAIv; 5 weeks with peak prevalence of 28% and 30% mortality) than LPAIv (8 weeks with peak prevalence of 50%). These findings indicate it is harder to detect HPAIv than LPAIv with swabs from live birds, which are commonly used during disease surveillance. Synthesis and applications . Our study highlights the potential of integrating incomplete surveillance data with epizootic models to quantify disease transmission and immunity. This modelling approach provides an important tool to understand spatial and temporal epizootic dynamics and inform disease surveillance. Our findings suggest focusing highly pathogenic avian influenza virus (HPAIv) surveillance on postbreeding areas where mortality of immunologically naïve hatch-year birds is most likely to occur, and collecting serology to enhance HPAIv detection. Our modelling approach can integrate various types of disease data facilitating its use with data from other surveillance programs (as illustrated by the estimation of infection rate during an HPAIv outbreak in mute swans Cygnus olor in Europe).

Journal of Applied Ecology↗
USGS2026

A new inventory and conservation assessment of United States islands

To support conservation-focused research and management we developed a new 30-m resolution polygon data layer of the nonlacustrine and nonriverine islands of the United States, with associated attributes describing key physical and conservation geography characteristics. Islands were grouped into a three-tiered hierarchy of island regions (twelve), island provinces (twenty-eight), and individual islands (19,023). Islands were classified as either continental or oceanic based on their physiographic position relative to the North America continental shelf, and estuarine versus nonestuarine depending on their location within or external to estuaries. For each island we assessed the diversity of terrestrial and coastal ecosystems, the number of threatened and endangered (T&E) species listed under the Endangered Species Act, the number of T&E species critical habitats, the number of migratory bird species listed under the Migratory Bird Treaty Act, the number of Key Biodiversity Areas, and the number of and management responsibility for protected areas. We conclude that the conservation importance of islands is disproportionate to their total area as, for example, islands contain 52 percent of the T&E species yet their total area is only 2 percent of the area of the continental mainland. Similarly, of the global total of 431 World Terrestrial Ecosystems, 201 (47 percent) occur on U.S. islands compared with 286 (66 percent) that occur on the U.S. continental mainland.

Annals of the American Association of Geographers↗
USGS1996

The management of hunting of Anatidae

The objectives of harvest management for members of family Anatidae typically involve the size of the harvested population and the size of the harvest. Hunting regulations are the primary tool used to try to achieve the objectives of harvest management. Informed harvest management thus requires a knowledge of the relationship between hunting regulations and both Anatid abundance and harvest. Results of retrospective studies in North America provide evidence that generally restrictive regulations produce lower harvest rates than generally liberal regulations. However, such studies have provided little evidence that specific hunting regulations designed to produce a change in the relative harvest rates of different species, or of the sexes within a species, have been successful in 'directing' harvest toward specific groups of birds and away from other groups. Estimates of the strength of the relationship between harvest mortality rates and annual survival rates of Anatidae have ranged from weak to strong. Thus, the key relationships for harvest management of Anatidae, those between hunting regulations and the size of both the subsequent harvest and the subsequent population, are not 'known' but are characterized by uncertainty. In the United States, this uncertainty led to a risk-aversive conservatism that characterized the setting of hunting regulations during the last decade. Recently, managers have begun to consider using hunting regulations themselves as a means to better understand the system being managed. This approach, referred to as active adaptive management, attempts to balance short-term demands for hunting opportunity with the learning needed to improve long-term management performance. Learning is accomplished by periodically comparing observed system response, as estimated by ongoing survey and data collection programs, with predictions of competing models. These periodic comparisons lead to changes in measures of credibility associated with the different models and thus to a reduction in uncertainty. We suggest that this approach might be useful in other countries that have implemented requisite data collection programs for their Anatid populations.

Book chapter↗
USGS1995

Winter population trends of selected songbirds

Many studies have found significant changes, primarily declines, in populations of breeding birds throughout the United States. Most studies have focused on birds that migrate to the Neotropics for winter. Speculations about causes of observed declines have primarily implicated habitat fragmentation and loss (e.g. deforestation) in Central and South America. The National Audubon Society's Christmas Bird Counts (CBC), begun in the winter of 1900-01, provide the data needed to discern consistent population trends in birds wintering throughout the United States. For this study we used the CBC data to examine population trends of songbirds with ranges that apparently are limited by lower temperatures in the North. We chose these species to track populations of birds that could be in peril in the future. These birds potentially will be more quickly affected by changing climate than other birds, and we need baseline information on them to document possible consequences of global climatic change. The species that are indeed declining need to be monitored because the possible synergistic effects of declining populations and changing climate could result in local and even regional extinctions.

Book chapter↗
USGS2004

Cormorant predation and the population dynamics of walleye and yellow perch in Oneida Lake

Double-crested Cormorants ( Phalacrocorax auritus ) increased dramatically in North America during the 1990s, providing the opportunity to study the effects of an increase of a top predator on an existing predator-prey system. In Oneida Lake, New York, USA, Double-crested Cormorants were first observed nesting in 1984 and had increased to over 360 nesting pairs by 2000. Concomitant with this increase in piscivorous birds was a decrease in the adult walleye ( Stizostedion vitreum ) and yellow perch ( Perca flavescens ) populations. Analysis of a 40-yr data series shows higher mortality of subadults (age 1-2 yr perch and age 1-3 yr walleye) for both species in the 1990s compared to the previous three decades. Cormorant diet was investigated from 1995 to 2000 using a combination of cast pellets, regurgitants, and stomach analysis. Walleye and yellow perch were a major portion of the cormorant diet during these years (40-82% by number). The number of subadult walleye and yellow perch consumed by cormorants suggests that the increase in subadult mortality can be explained by predation from cormorants. Mean mortality rates of adult percids attributed to cormorant predation were 1.1% per year for walleye and 7.7% per year for yellow perch. Our analysis suggests that predation by cormorants on subadult percids is a major factor contributing to the decline in both the walleye and the yellow perch populations in Oneida Lake. Other ecosystem changes (zebra mussels, lower nutrient loading, decrease in alternate prey) are not likely explanations because the potential mechanisms involved are not consistent with auxiliary data from the lake and would not affect subadult mortality. The likely impact of bird predation on percid populations in Oneida Lake occurs because cormorants feed on larger fish that are beyond the size range where compensatory mechanisms are important.

New York↗
USGS1995

Are red-tailed hawks and great horned owls diurnal-nocturnal dietary counterparts?

Red-tailed Hawks (Buteo jamaicensis) and Great Homed Owls (Bubo virginianus)are common in North America where they occupy a wide range of habitats, often sympatrically. The two species are similar in size and have been portrayed as ecological counterparts, eating the same prey by day and night. We tested the trophic similarity of the two species by comparing published dietary data from across the United States. Both species ate primarily mammals and birds, and mean proportions of those two prey types did not differ significantly between diets of the two raptors. Red-tailed Hawks ate significantly more reptiles, and Great Homed Owls significantly more invertebrates. Dietary diversity was not significantly different at the level of prey taxonomic class, and diet overlap between the two species averaged 91%. At the prey species level, dietary overlap averaged only 50%, and at that level Red-tailed Hawk dietary diversity was significantly greater than that of Great Horned Owls. Mean prey mass of Red-tailed Hawks was significantly greater than that of Great Homed Owls. Populations of the two species in the western United States differed trophically more than did eastern populations. We conclude that, although the two species are generalist predators, they take largely different prey species in the same localities resulting in distinctive trophic characteristics.

The Wilson Bulletin↗
USGS1989

The impact of eastern equine encephalitis virus on efforts to recover the endangered whooping crane

The whooping crane (Grus americana), although never abundant in North America, became endangered primarily because of habitat modification and destruction. To help recovery, a captive propagation and reintroduction program was initiated at the Patuxent Wildlife Research Center (PWRC) in 1966. However, in 1984, 7 of 39 whooping cranes at PWRC died from infection by eastern equine encephalitis (EEE) virus, an arbovirus that infects a wide variety of indigenous bird species, although mortality is generally restricted to introduced birds. Following identification of the aetiological agent, surveillance and control measures were implemented, including serological monitoring of both wild and captive birds for EEE viral antibody and assay of locally-trapped mosquitoes for virus. In addition, an inactivated EEE virus vaccine developed for use in humans was evaluated in captive whooping cranes. Results so far suggest that the vaccine will afford protection to susceptible birds.

Book chapter↗
USGS2014

North Atlantic migratory bird flyways provide routes for intercontinental movement of avian influenza viruses

Avian influenza virus (AIV) in wild birds has been of increasing interest over the last decade due to the emergence of AIVs that cause significant disease and mortality in both poultry and humans. While research clearly demonstrates that AIVs can move across the Pacific or Atlantic Ocean, there has been no data to support the mechanism of how this occurs. In spring and autumn of 2010 and autumn of 2011 we obtained cloacal swab samples from 1078 waterfowl, gulls, and shorebirds of various species in southwest and west Iceland and tested them for AIV. From these, we isolated and fully sequenced the genomes of 29 AIVs from wild caught gulls (Charadriiformes) and waterfowl (Anseriformes) in Iceland. We detected viruses that were entirely (8 of 8 genomic segments) of American lineage, viruses that were entirely of Eurasian lineage, and viruses with mixed American-Eurasian lineage. Prior to this work only 2 AIVs had been reported from wild birds in Iceland and only the sequence from one segment was available in GenBank. This is the first report of finding AIVs of entirely American lineage and Eurasian lineage, as well as reassortant viruses, together in the same geographic location. Our study demonstrates the importance of the North Atlantic as a corridor for the movement of AIVs between Europe and North America.

North Atlantic↗
USGS1999

Covariance of lichen and vascular plant floras

The geographic relationships among taxonomic groups are important to study to determine patterns of biodiversity and whether or not associations occur between large groups, e.g., birds and vascular plants. This study was undertaken to determine relationships between higher plants and lower plants, specifically vascular plant and lichen floras in nine national parks of the Great Lakes region. No significant relationship was found between vascular plant floras and lichen floras in this area, which spans 1200 km longitudinally, or between an additional 19 areas from North America that were less than 1000 km(2) in area. For areas larger than 1000 km(2), however, a significant positive relationship existed for 33 areas that span one to approximately 150 million km(2). The ratio of numbers of vascular plants to lichens appeared to average just over 6 across the 33 areas. In the Great Lakes parks, between 28-30% of either the vascular plant or lichen species were singletons (occurring in only one park), but the parks that contained the most singletons were not congruent: Isle Royale had the most singleton lichens, while Indiana Dunes had the most vascular plant singletons. Fewer lichen species (2%) than vascular plants (4%) occurred in all nine parks. Latitude appeared to explain some of the variation between the two groups: vascular plants decreased with increasing latitude, while lichens increased.

Illinois, Indiana, Michigan, Minnesota, Ohio, Wisc↗
USGS2022

Interpreting long-distance movements of non-migratory golden eagles: Prospecting and nomadism?

Movements by animals can serve different functions and occur over a variety of spatial and temporal scales. Routine movement types, such as residency (localized movements) and migration, have been well studied. However, nonroutine movement types, such as dispersal, prospecting, and nomadism, are less well understood. Documenting these rarely detected events requires tracking large numbers of individuals across all age classes. We studied >500 golden eagles ( Aquila chrysaetos ) tracked by telemetry over a 10-year period in western North America, of which 160 engaged in nonroutine, long-distance (>300 km) movements. We identified spatial and temporal correlates of those movements at both small and large scales, and we quantified movement timing and direction. We further tested which age and sex classes of eagles were more likely to engage in these movements. Our analysis of 88,093 daily tracks suggested that distances traveled by eagles were responsive to the updraft potential of the spatial and temporal landscape they encountered. Tracks covered longer distances at locations and times of higher updraft potential, and older birds traveled farther than younger birds. By contrast, after decomposing daily tracks into 563 nonroutine, long-distance movements measured at a multiday scale, only the duration of travel was responsive to environmental conditions encountered by eagles. Multiday trips that were longer were those initiated in open and warm landscapes and those that ended in mountainous regions. Finally, long-distance movements were more frequently made in seasons other than winter, in north–south directions, and by young birds. We documented clear correlates of nonroutine, long-distance movements by golden eagles at small, local scales but found little evidence of such correlates at larger, regional scales. Most long-distance movements we documented fit patterns associated with traditional definitions of prospecting and nomadism but not migration. Our study is the first to describe these movement types by golden eagles, and as such provides a foundation for subsequent study into the movement ecology of other species.

Ecosphere↗
USGS2003

Oral biology and beak disorders of birds

The beak, or bill, of the bird is a complicated structure. The avian skull is described as having some reptilian features; this includes a quadrate bone that articulates with the articular bone of the lower jaw.

Veterinary Clinics of North America: Exotic Animal↗
USGS2021

Small shorebirds feast on green slime to fuel their long migration

Shorebirds wade in shallow waters along shorelines searching for food. More than a million shorebirds visit the San Francisco Estuary each year during their migration to feast on the insects, worms, clams, and crabs that live on or under the surface of the sand or mud. The abundant food in the Estuary provides shorebirds with the energy they need to migrate thousands of kilometers, between their breeding areas in the Arctic and their wintering areas along the Pacific coast of North and South America. Scientists have discovered that, during migration, small species of shorebirds eat a green slime called biofilm that grows on the surface of the mud. Larger shorebirds do not eat biofilm. This article describes how the bills and tongues of small shorebirds help them eat biofilm, what biofilm is, and why biofilm is an important food for those birds during migration.

Frontiers for Young Minds↗
USGS2004

Redistribution and growth of the Caspian Tern population in the Pacific Coast region of North America, 1981-2000

We examined nesting distribution and demography of the Pacific Coast population of Caspian Terns ( Sterna caspia ) using breeding records and band recoveries spanning two decades since the first population assessment. Since 1980, population size has more than doubled to about 12 900 pairs, yet the proportion of the population nesting at inland (18%) versus coastal sites (82%) has remained constant. Although the breeding range of the Pacific Coast population has expanded northward into Alaska and farther south in Mexico, there was no net latitudinal shift in the distribution of breeding pairs or new colonies. The distribution of breeding birds among areas changed dramatically, however, with 69% of breeding terns now nesting in Oregon (primarily in the Columbia River estuary) versus 4% during the late 1970s. During the past 20 years, there has continued to be a greater proportion of Caspian Terns breeding at anthropogenic sites compared to natural sites. Estimated annual survival rates for hatch-year and after-third-year birds during 1981-1998 were greater than during 1955-1980, consistent with the higher rate of population increase in recent decades. Fecundity required to maintain a stable population ( λ = 1 ) was estimated at 0.32–0.74 fledglings pair −1 , depending on band recovery probabilities for sub-adults. Caspian Terns readily moved among breeding sites and rapidly colonized new areas; however, a greater concentration of breeding Caspian Terns among fewer colonies in response to anthropogenic factors is an important conservation concern for this species.

Condor↗
USGS2019

Conservation challenges emerging from free-roaming horse management: a vexing social-ecological mismatch

Horses have been associated with human societies for millennia, and for many have come to symbolize wildness, power, resilience, and freedom. Although equids were extirpated from North America 10 000-12 000 years ago, descendants of domestic horses now roam freely in the USA and 17 other countries across six continents. In landscape-scale and experimental investigations, free-roaming horses (Equus caballus) have been shown to induce numerous alterations to native-ecosystem components and processes through influences on soil, water, plants, native ungulates, small mammals, birds, reptiles, and other aspects of biodiversity. However, we argue that the management of free-roaming horses both in the U.S. and globally has been complicated by “socio-ecological mismatches.” These three mismatches stem from discrepancies between: 1) steady-state (horse-management) goals vs. a stochastically variable environment; 2) different methods to evaluate evidence, resolve conflicting beliefs, and achieve objectives, in scientific vs. political processes; and 3) differing spatial and temporal scales between policy and management, and values of science vs. values of the general public. Such mismatches arise from an inability to reconcile conflicting processes and functions in a social-ecological system, often reflecting differences in the spatio-temporal scales at which diverse components operate. Here, we describe three types of mismatches, and illustrate how the ecological dynamics of aridlands generally fit poorly with existing approaches to horse management and policy. Such mismatches complicate cost-effective management of free-roaming horses and the ecosystems they inhabit, and reduce the palette of potential solutions.

Conservation Letters↗
USGS2024

Antibodies to influenza A virus in Lesser (Aythya affinis) and Greater Scaup (Aythya marila) in the USA

Scaup, including both Lesser and Greater ( Aythya affinis and Aythya marila , respectively), are a grouping of populous and widespread North American diving ducks. Few influenza type A viruses (IAV) have been reported from these species despite a high prevalence of antibodies to IAV being reported. Existing virologic and serologic data indicate that IAV infection routinely occurs in scaup, yet it is unknown which IAV subtypes are linked to these infections. In this study, we aimed to gain a more complete picture of IAV natural history in Lesser and Greater Scaup from two coastal flyways in North America in 2015–18 (302 samples from California in the Pacific Flyway and 471 samples from Maryland in the Atlantic Flyway). Low prevalence of active IAV infection was detected by real-time reverse-transcription PCR in Lesser Scaup sampled in Maryland and California (2.8% and 8.1%, respectively). A single IAV (H1N1) was isolated in embryonated chicken eggs from a bird sampled in California. Similarly low levels were observed in Greater Scaup in California (3.3%). Antibodies to the nucleoprotein as detected with a commercial blocking ELISA were observed in all species and flyway combinations. Antibody seroprevalence estimates were higher in adult Lesser Scaup than in juveniles at both the ≤0.5 ( P <0.001, z=–3.582) and ≤0.7 serum-sample-to-negative-control absorbance thresholds ( P =0.003, z=–2.996). Neutralizing antibodies to H1–H12, H14, and H15 were detected using a microtiter virus neutralization assay, with the highest prevalence of antibodies against H1 (38%), H6 (36%), and H11 (35%). The high prevalence of antibodies to IAV and evidence of previous exposure to numerous subtypes are consistent with a high level of population immunity and a low prevalence of infection. These results must be interpreted in the context of season (winter sampling), as results may vary with the annual influx of naïve juvenile birds.

California, Maryland↗
USGS2003

Effects of management practices on grassland birds: Greater Prairie-Chicken

Information on the habitat requirements and effects of habitat management on grassland birds were summarized from information in more than 5,500 published and unpublished papers. A range map is provided to indicate the breeding distribution of Greater Prairie-Chicken in the United States and southern Canada. Although birds frequently are observed outside the breeding range indicated, the maps are intended to show areas where managers might concentrate their attention. It may be ineffectual to manage habitat at a site for a species that rarely occurs in an area. The species account begins with a brief capsule statement, which provides the fundamental components or keys to management for the species. A section on breeding range outlines the current breeding distribution of the species in North America. The suitable habitat section describes the breeding habitat and occasionally microhabitat characteristics of the species, especially those habitats that occur in the Great Plains. Details on habitat and microhabitat requirements often provide clues to how a species will respond to a particular management practice. A table near the end of the account complements the section on suitable habitat, and lists the specific habitat characteristics for the species by individual studies. A special section on prey habitat is included for those predatory species that have more specific prey requirements. The area requirements section provides details on territory and home range sizes, minimum area requirements, and the effects of patch size, edges, and other landscape and habitat features on abundance and productivity. It may be futile to manage a small block of suitable habitat for a species that has minimum area requirements that are larger than the area being managed. The section on breeding-season phenology and site fidelity includes details on spring arrival and fall departure for migratory populations in the Great Plains, peak breeding periods, the tendency to renest after nest failure or success, and the propensity to return to a previous breeding site. The duration and timing of breeding varies among regions and years. Species&rsquo; response to management summarizes the current knowledge and major findings in the literature on the effects of different management practices on the species. The section on management recommendations complements the previous section and summarizes specific recommendations for habitat management provided in the literature. If management recommendations differ in different portions of the species&rsquo; breeding range, recommendations are given separately by region. The literature cited contains references to published and unpublished literature on the management effects and habitat requirements of the species. This section is not meant to be a complete bibliography; a searchable, annotated bibliography of published and unpublished papers dealing with habitat needs of grassland birds and their responses to habitat management is posted at the Web site mentioned below.

Kansas, Oklahoma, Colorado, Missouri, Illinois, Wi↗