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At least 865 records · Page 48Linked to original sources

USGS2026

Mortality in the Hawaiian Short-eared Owl (Pueo, Asio flammeus sandwichensis): Causes and spatial trends

Trends in wildlife mortality can be particularly challenging to identify in low-density species where mortalities are less likely to be detected or documented. The Pueo, or Hawaiian Short-eared Owl ( Asio flammeus sandwichensis ), is the only native raptor that breeds on all the main Hawaiian Islands. The Pueo is state-listed as endangered on the island of Oʻahu, but drivers of population dynamics are not well known, including causes of mortality. In this study, existing records from organizations across the Hawaiian Islands were compiled to evaluate the causes of mortality in Pueo. Here, 242 unique records spanning the years 1993 to 2024 from state, federal, and private organizations were evaluated for causes of Pueo death. Trauma due to collisions with vehicles, wind turbines, fences, and other human-made objects was the leading detected cause of death (62%) followed by emaciation (13%) and disease (6%), with 19% of deaths due to unknown causes. The islands of Hawaiʻi and Kauaʻi, both with relatively low human populations, had the highest total number of reported mortalities (n = 77, 32%). The highest number of recorded mortalities was in the month of July (16%), and mortalities were generally higher from June through August. Although our study has detection biases, our results are consistent with global studies suggesting that blunt force trauma from vehicles, wind turbines, and other infrastructure are potentially important sources of mortality in raptors. Similar to other studies, rodenticide effects and infectious disease were potentially underestimated as sources of mortality, because most birds did not undergo a full necropsy. Further, there may be confounding variables due to ad hoc data collection. Development of a state-wide system for reporting and recording wildlife mortality along with future studies that include necropsies may improve our ability to discern which sources of mortality may be mitigated.

Hawaii↗

USGS1980

Decline and disappearance of the Dusky Seaside Sparrow from Merritt Island, Florida

The Dusky Seaside Sparrow, Ammospiza maritima nigrescens , was first discovered by Charles J. Maynard near Salt Lake on the St. Johns River west of Titusville, Brevard County, Florida, on March 17, 1872. Later that spring, Maynard found the sparrow to be quite common in the salt marsh on the Canaveral Peninsula in what is now the Merritt Island National Wildlife Refuge on the John F. Kennedy Space Center. The first Dusky nests were found 42 years later when Oscar E. Baynard and Henry Simpson located three on the peninsula along the edge of Indian River on May 21, 1914. The sparrow was abundant in the marsh on the east of the Indian River until the 1950s. By the early 1960s, the sparrow had disappeared from much of its former range and a decline occurred in an area under study on Merritt Island.

American Birds↗

USGS2022

Drivers of flight performance of California Condors (Gymnogyps californianus)

Flight behavior of soaring birds depends on a complex array of physiological, social, demographic, and environmental factors. California Condors ( Gymnogyps californianus ) rely on thermal and orographic updrafts to subsidize extended bouts of soaring flight, and their soaring flight performance is expected to vary in response to environmental variation and, potentially, with experience. We collected 6298 flight tracks described by high-frequency GPS telemetry data from five birds ranging in age from 1 to 19 yr old and followed over 32 d in summer 2016. Using these data, we tested the hypothesis that climb rate, an indicator of flight performance, would be related to the topographic and meteorological variables the bird experienced, and also to its age. Climb rate was greater when condors were flying in faster winds and during environmental conditions that were conducive to updraft development. However, we found no effect of age on climb rate. Although many of these relationships were expected based on flight theory, the lack of an effect of age was unexpected. Our work expands understanding of the relationship condors have with the environment, and it also suggests the potential for as-yet unexplored complexity to this relationship. As such, this study provides insight into avian flight behavior and, because flight performance influences bird behavior and exposure to anthropogenic risk, it has potential consequences for development of conservation management plans.

California↗

USGS2018

Use of created snags by cavity‐nesting birds across 25 years

Snags are important habitat features for many forest‐dwelling species, so reductions in the number of snags can lead to the loss of biodiversity in forest ecosystems. Intentional snag creation is often used in managed forests to mitigate the long‐term declines of naturally created snags, yet information regarding the use of snags by wildlife across long timescales (>20 yr) is lacking and prevents a complete understanding of how the value of created snags change through time. We used a long‐term experiment to assess how harvest treatment (i.e., small‐patch group selection, 2‐story, and clearcut) and snag configuration (i.e., scattered and clustered) influenced nesting in and foraging on 25–27‐year‐old Douglas‐fir ( Pseudotsuga menziesii ) snags by cavity‐nesting birds. In addition, we compared our contemporary measures of bird use to estimates obtained from historical surveys conducted on the same group of snags to quantify how bird use changed over time. Despite observing created snags for >750 hours across 2 consecutive breeding seasons, we found limited evidence of nesting activity. Only 11% of created snags were used for breeding, with nesting attempts by 4 bird species ( n = 36 nests); however, we detected 12 cavity‐nesting species present on our study sites. Furthermore, nearly all nests (94%) belonged to the chestnut‐backed chickadee ( Poecile rufescens ), a weak cavity‐excavating species that requires well‐decayed wood for creating nest cavities. Our surveys also recorded few observations of birds using created snags as foraging substrates, with only 1 foraging event recorded for every 20 hours of observation. We detected 82% fewer nests and recorded 7% fewer foraging observations during contemporary field work despite spending >7.5 times more effort observing created snags relative to historical surveys. We conclude that 25–27‐year‐old created Douglas‐fir snags provided limited opportunities for nesting and foraging by most cavity‐nesting birds, and that the period of greatest use by this group occurred within 5–15 years of creation.

Journal of Wildlife Management↗

USGS2010

Landscape-level impact of tropical forest loss and fragmentation on bird occurrence in eastern Guatemala

Tropical forest destruction and fragmentation of habitat patches may reduce population persistence at the landscape level. Given the complex nature of simultaneously evaluating the effects of these factors on biotic populations, statistical presence/absence modelling has become an important tool in conservation biology. This study uses logistic regression to evaluate the independent effects of tropical forest cover and fragmentation on bird occurrence in eastern Guatemala. Logistic regression models were constructed for 10 species with varying response to habitat alteration. Predictive variables quantified forest cover, fragmentation and their interaction at three different radii (200, 500 and 1000 m scales) of 112 points where presence of target species was determined. Most species elicited a response to the 1000 m scale, which was greater than most species’ reported territory size. Thus, their presence at the landscape scale is probably regulated by extra-territorial phenomena, such as dispersal. Although proportion of forest cover was the most important predictor of species’ presence, there was strong evidence of area-independent and -dependent fragmentation effects on species presence, results that contrast with other studies from northernmost latitudes. Species’ habitat breadth was positively correlated with AIC model values, indicating a better fit for species more restricted to tropical forest. Species with a narrower habitat breadth also elicited stronger negative responses to forest loss. Habitat breadth is thus a simple measure that can be directly related to species’ vulnerability to landscape modification. Model predictive accuracy was acceptable for 4 of 10 species, which were in turn those with narrower habitat breadths.

Cerro San Gil Watershed Protection Reserve↗

USGS2000

Landscape correlates of breeding bird richness across the United States mid-Atlantic region

Using a new set of landscape indicator data generated by the U.S.EPA, and a comprehensive breeding bird database from the National Breeding Bird Survey, we evaluated associations between breeding bird richness and landscape characteristics across the entire mid-Atlantic region of the United States. We evaluated how these relationships varied among different groupings (guilds) of birds based on functional, structural, and compositional aspects of individual species demographics. Forest edge was by far the most important landscape attribute affecting the richness of the lumped specialist and generalist guilds; specialist species richness was negatively associated with forest edge and generalist richness was positively associated with forest edge. Landscape variables (indicators) explained a greater proportion of specialist species richness than the generalist guild (46% and 31%, respectively). The lower value in generalists may reflect freer-scale distributions of open habitat that go undetected by the Landsat satellite, open habitats created by roads (the areas from which breeding bird data are obtained), and the lumping of a wide variety of species into the generalist category. A further breakdown of species into 16 guilds showed considerable variation in the response of breeding birds to landscape conditions; forest obligate species had the strongest association with landscape indicators measured in this study (55% of the total variation explained) and forest generalists and open ground nesters the lowest (17% of the total variation explained). The variable response of guild species richness to landscape pattern suggests that one must consider species' demographics when assessing the consequences of landscape change on breeding birds.Using a new set of landscape indicator data generated by the U.S. EPA, and a comprehensive breeding bird database from the National Breeding Bird Survey, we evaluated associations between breeding bird richness and landscape characteristics across the entire mid-Atlantic region of the United States. We evaluated how these relationships varied among different groupings (guilds) of birds based on functional, structural, and compositional aspects of individual species demographics. Forest edge was by far the most important landscape attribute affecting the richness of the lumped specialist and generalist guilds; specialist species richness was negatively associated with forest edge and generalist richness was positively associated with forest edge. Landscape variables (indicators) explained a greater proportion of specialist species richness than the generalist guild (46% and 31%, respectively). The lower value in generalists may reflect finer-scale distributions of open habitat that go undetected by the Landsat satellite, open habitats created by roads (the areas from which breeding bird data are obtained), and the lumping of a wide variety of species into the generalist category. A further breakdown of species into 16 guilds showed considerable variation in the response of breeding birds to landscape conditions; forest obligate species had the strongest association with landscape indicators measured in this study (55% of the total variation explained) and forest generalists and open ground nesters the lowest (17% of the total variation explained). The variable response of guild species richness to landscape pattern suggests that one must consider species' demographics when assessing the consequences of landscape change on breeding birds.

Conference Paper↗

USGS2012

Hatching and fledging times from grassland passerine nests

1 day and was positively correlated with clutch size. Length of the fledging period for a brood was usually <1 day, and in nearly half the nests, fledging was completed within <2 hr. Video surveillance has proven to be a useful tool for providing new information and for corroborating published statements related to hatching and fledging chronology. Comparison of data collected from video and nest visits showed that carefully conducted nest visits generally can provide reliable data for deriving estimates of survival."}" data-sheets-userformat="{"2":8403202,"4":[null,2,16777215],"11":4,"14":[null,2,0],"15":"Inconsolata, monospace, arial, sans, sans-serif","16":11,"26":400}" data-sheets-formula="=VLOOKUP(R[0]C[-5],Fixed!R2C[-6]:C[-4],3,false)">Accurate estimates of fledging age are needed in field studies to avoid inducing premature fledging or missing the fledging event. Both may lead to misinterpretation of nest fate. Correctly assessing nest fate and length of the nestling period can be critical for accurate calculation of nest survival rates. For researchers who mark nestlings, knowing the age at which their activities may cause young to leave nests prematurely could prevent introducing bias to their studies. We obtained estimates of fledging age using data from grassland bird nests monitored from hatching through fledging with video-surveillance systems in North Dakota and Minnesota during 1996–2001. We compared these values to those obtained from traditional nest visits and from available literature. Mean and modal fledging ages for video-monitored nests were generally similar to those for visited nests, although Clay-colored Sparrows (Spizella pallida) typically fledged 1 day earlier from visited nests. Average fledging ages from both video and nest visits occurred within ranges reported in the literature, but expanded by 1–2 days the upper age limit for Clay-colored Sparrows and the lower age limit for Bobolinks (Dolichonyx oryzivorus). Video showed that eggs hatched throughout the day whereas most young fledged in the morning (06:30–12:30 CDT). Length of the hatching period for a clutch was usually >1 day and was positively correlated with clutch size. Length of the fledging period for a brood was usually <1 day, and in nearly half the nests, fledging was completed within <2 hr. Video surveillance has proven to be a useful tool for providing new information and for corroborating published statements related to hatching and fledging chronology. Comparison of data collected from video and nest visits showed that carefully conducted nest visits generally can provide reliable data for deriving estimates of survival.

Studies in Avian Biology↗

USGS2002

Final report: Initial ecosystem response of salt marshes to ditch plugging and pool creation: Experiments at Rachel Carson National Wildlife Refuge (Maine)

This study evaluates the response of three salt marshes, associated with the Rachel Carson National Wildlife Refuge (Maine), to the practice of ditch plugging. Drainage ditches, originally dug to drain the marsh for mosquito control or to facilitate salt hay farming, are plugged with marsh peat in an effort to impound water upstream of the plug, raise water table levels in the marsh, and increase surface water habitat. At two study sites, Moody Marsh and Granite Point Road Marsh, ditch plugs were installed in spring 2000. Monitoring of hydrology, vegetation, nekton and bird utilization, and marsh development processes was conducted in 1999, before ditch plugging, and then in 2000 and 2001 (all parameters except nekton), after ditch plugging. Each study site had a control marsh that was monitored simultaneously with the plugged marsh, and thus, we employed a BACI study design (before, after, control, impact). A third site, Marshall Point Road Marsh, was plugged in 1998. Monitoring of the plugged and control sites was conducted in 1999 and 2000, with limited monitoring in 2001, thus there was no ?before? plug monitoring. With ditch plugging, water table levels increased toward the marsh surface and the areal extent of standing water increased. Responding to a wetter substrate, a vegetation change from high marsh species (e.g., Spartina patens) to those more tolerant of flooded conditions (e.g., Spartina alterniflora) was noted at two of the three ditch plugged sites. Initial response of the nekton community (fishes and decapod crustaceans) was evaluated by monitoring utilization of salt marsh pools using a 1m2 enclosure trap. In general, nekton species richness, density, and community structure remained unchanged following ditch plugging at the Moody and Granite Point sites. At Marshall Point, species richness and density (number of individuals per m2) were significantly greater in the experimental plugged marsh than the control marsh (<2% of the control marsh was open water habitat vs. 11% of the plugged marsh). The response of birds, categorized as waterfowl & waterbirds, shorebirds & wading birds, gulls & terns, and miscellaneous (raptors, passerines, other), was variable. Following ditch plugging, bird species richness increased at the Granite Point site (1999 pre-plug = 15.4, 2000 post-plug = 26.2, 2001 post-plug = 38.7). Because of a low sample size at Moody Marsh, reliable statements on species richness cannot be made. Density of birds (no. of birds per ha) remained unchanged with ditch plugging at Granite Point Marsh, although there was a strong, but not statistically significant, trend toward increased density. This study only reports on initial responses of marsh functions to ditch plugging. Monitoring should continue at these sites, and perhaps at additional sites, for the next decade or so. A monitoring plan is recommended. Long-term monitoring will include evaluation of salt marsh development processes using SET (surface elevation table) methodology. There is concern, although not confirmed, that as ditch-plugged marshes become wetter and marsh grass production declines their ability to keep pace with sea level rise could be jeopardized. It is suggested that ditch plugging should be considered an experimental marsh management technique. Additional monitoring on the physical and habitat responses of ditch-plugged marshes is required, along with assessments of other techniques aimed at restoring open water habitat to the marsh surface.

Book↗

USGS2002

Avian vacuolar myelinopathy: a newly recognized fatal neurologic disease of eagles, waterfowl, and other birds

Wildlife biologists and health specialists have been frustrated by a long list of negative findings in their AVM investigations, however studies continue to provide pieces of information to aid the determination of the cause and its source. Available data indicated that AVM may have been present since at least 1990, occurs in at least five states, has been documented during October through April at sites of wintering populations of birds where the exposure apparently occurs, and has killed at least 90 bald eagles. Birds with AVM have difficulty or inability to fly, swim, walk, or perch, but there has been resolution of clinical signs in some affected coots. The list of affected species continues to grow, but remains confined to wild avians, including bald eagle, American coot, great horned owl, killdeer, Canada goose, mallard, ring-necked duck and bufflehead. The effects of the AVM agent on mammals, including human beings, are unknown. A neurotoxicant of manmade or natural origin is the suspected cause of AVM because no infectious disease agents, such as viruses, bacteria, parasites and prions, have been found, and the lesion and epizootiology of AVM resemble those of toxicoses. Additionally it is documented, experimentally, that exposure to raptors can occur through ingestion of infected coots. Collaborative studies will continue in the effort to identify the cause of AVM, its geographic distribution, and the range of species susceptibility. Hopefully, this information can be used to identify measures that might be taken to reduce the impact of AVM on the wildlife resource. Multiple agencies, institutions, and individuals must rely on each other's expertise in the multidisciplinary approach to this problem, persevere in their efforts and take advantage of serendipity that presents itself during investigations of this newly recognized cause of wild bird mortality.

Arkansas, Georgia, North Carolina, South Carolina↗

USGS2016

Immunoglobulin detection in wild birds: Effectiveness of three secondary anti-avian IgY antibodies in direct ELISAs in 41 avian species

1.Immunological reagents for wild, non-model species are limited or often non-existent for many species. 2. In this study, we compare the reactivity of a new anti-passerine IgY secondary antibody with existing secondary antibodies developed for use with birds. Samples from 41 species from the following six avian orders were analysed: Anseriformes (1 family, 1 species), Columbiformes (1 family, 2 species), Galliformes (1 family, 1 species), Passeriformes (16 families, 34 species), Piciformes (1 family, 2 species) and Suliformes (1 family, 1 species). Direct ELISAs were performed to detect total IgY using goat anti-passerine IgY, goat anti-chicken IgY or goat anti-bird IgY secondary antibodies. 3.The anti-passerine antibody exhibited significantly higher IgY reactivity compared to the anti-chicken and/or anti-bird antibodies in 80% of the passerine families tested. Birds in the order Piciformes (woodpeckers) and order Suliformes (cormorants) were poorly detected by all three secondary antibodies. A comparison of serum and plasma IgY levels was made within the same individuals for two passerine species (house finch and white-crowned sparrow), and serum exhibited significantly more IgY than the plasma for all three secondary antibodies. This result indicates that serum may be preferred to plasma when measuring total antibody levels in blood. 4.This study indicates that the anti-passerine IgY secondary antibody can effectively be used in immunological assays to detect passerine IgY for species in most passerine families and is preferred over anti-chicken and anti-bird secondary antibodies for the majority of passerine species. This anti-passerine antibody will allow for more accurate detection and quantification of IgY in more wild bird species than was possible with previously available secondary antibodies.

Methods in Ecology and Evolution↗

USGS2022

Nest remains are insufficient to identify predators of waterfowl nests

Context: Nest predation is a leading cause of nest failure for most ground-nesting birds. Methods that allow for accurate classification of fate and identification of predators are important for understanding productivity and conservation strategies. Past studies have used a visual inspection of nest remains to determine nest fate and predict predator identity. Most formal assessments of these methods have addressed small-bodied birds nesting in trees or shrubs, and have revealed that use of evidence at nests can be relatively accurate for determining nest fate but may lead to incorrect conclusions regarding predator identity. However, few have tested the latter hypothesis for larger ground-nesting birds with precocial young. Aim: We aimed to evaluate a classification system developed for determining nest fate and identifying predators of waterfowl nests, at both the scale of individual nests and across the study area. Methods: From 2016 to 2020, we located 989 blue-winged teal ( Spatula discors ), mallard ( Anas platyrhynchos ) and gadwall ( Mareca strepera ) nests in central North Dakota. We placed cameras at a subset of 249 nests and recorded evidence of nest remains at depredated nests. Key results: The most common predators were American badgers ( Taxidea taxus ), followed by striped skunks ( Mephitis mephitis ), raccoons ( Procyon lotor ) and red foxes ( Vulpes vulpes ). Using evidence of nest remains, we determined nest fates with high accuracy (98.0%). However, evidence of nest remains was only sufficient for identifying predators at 50% of nests, and the classification system was correct only 69.7% of the time. The predicted proportion of predators across the study area differed between the classification system and our video evidence as well. Conclusions: The accuracy of predator identifications based upon the classification system that we evaluated was not supported at any scale. Implications: Our results suggest that evidence of nest remains can be used to determine nest fate for large-bodied precocial, ground-nesting birds, but accurate identification of nest predators will require alternative methods such as nest cameras.

Wildlife Research↗

USGS2011

Semiochemical compounds of preen secretion reflect genetic make-up in a seabird species

Several vertebrates choose their mate according to genetic heterozygosity and relatedness, and use odour cues to assess their conspecifics' genetic make-up. In birds, although several species (including the black-legged kittiwake) exhibit non-random mating according to genetic traits, the cues used to assess genetic characteristics remain unknown. The importance of olfaction in birds' social behaviour is gaining attention among researchers, and it has been suggested that, as in other vertebrates, bird body scent may convey information about genetic traits. Here, we combined gas chromatography data and genetic analyses at microsatellite loci to test whether semiochemical messages in preen secretion of kittiwakes carried information about genetic heterozygosity and relatedness. Semiochemical profile was correlated with heterozygosity in males and females, while semiochemical distance was correlated with genetic distance only in male–male dyads. Our study is the first to demonstrate a link between odour and genetics in birds, which sets the stage for the existence of sophisticated odour-based mechanisms of mate choice also in birds.

Proceedings of the Royal Society B: Biological Sci↗

USGS2007

Status review of the Marbled Murrelet (Brachyramphus marmoratus) in Alaska and British Columbia

The Marbled Murrelet ( Brachyramphus marmoratus ) is a small, diving seabird inhabiting inshore waters of the Northeastern Pacific Ocean. This species feeds on small, schooling fishes and zooplankton, and nests primarily on the moss-covered branches of large, old-growth conifers, and also, in some parts of its range, on the ground. We reviewed existing information on this species to evaluate its current status in the northern part of its range—Alaska (U.S.) and British Columbia (Canada). Within the southern part of its range (Washington, Oregon, and California, U.S.), the Marbled Murrelet was listed as a threatened species under the Endangered Species Act (ESA) in 1993, and the U.S. Fish and Wildlife Service (USFWS) needed information on the species throughout its range for ESA deliberations. We compiled published information on the conservation status, population biology, foraging ecology, population genetics, population status and trends, demography, marine and nesting habitat characteristics, threats, and ongoing conservation efforts for Marbled Murrelets in Alaska and British Columbia. We conducted a new genetic study using samples from a segment of the range that had not been included in previous studies (Washington, Oregon) and additional nuclear intron and microsatellite markers. We also analyzed available at-sea survey data from several locations for trend. To understand the reasonableness of the empirical trend data, we developed demographic models incorporating stochasticity to discern what population trends were possible by chance. The genetic studies substantially confirmed previous findings on population structure in the Marbled Murrelet. Our present work finds three populations: (1) one comprising birds in the central and western Aleutian Islands; (2) one comprising birds in central California; and (3) one comprising birds within the center of the range from the eastern Aleutians to northern California. Our knowledge of genetic structure within this central population is limited and it requires additional study. Compiling available abundance information, we estimated that in the recent past, Marbled Murrelets in Alaska numbered on the order of 1 million birds. We were unable to generate a similar estimate for historical population size in British Columbia. Using trend information from at-sea surveys spanning a wide geographic range in Alaska, murrelet numbers declined significantly at five of eight trend sites at annual rates of -5.4 to -12.7 percent since the early 1990s. Applying these rates of decline to the historical population estimate, the current murrelet population in Alaska is projected to be on the order of 270,000 birds. This represents an overall population decline of about 70 percent during the past 25 years. In British Columbia, available trend data indicate that murrelet populations there have experienced similar declines. We updated a recent (2002) population estimate for British Columbia, concluding that there are now between 54,000 and 92,000 murrelets in British Columbia. The rates of decline we observed are within, but at the high end of, a range of rates expected by chance. Given that declines were estimated for sites over essentially the entire northern range of the species, there is cause for concern about the species’ status. In their marine habitats, Marbled Murrelets overlap with salmon (Oncorhynchus sp.) gillnetting operations in British Columbia and in Alaska (especially in Prince William Sound and Southeast Alaska), and annual bycatch mortality is likely in the low thousands per year, although bycatch rates are difficult to measure. The species’ inshore distribution coincides with high levels of vessel traffic and makes them especially vulnerable to both chronic oil pollution and to catastrophic spills (e.g., the 1989 Exxon Valdez oil spill [EVOS] in south-central Alaska, which is estimated to have killed 12,000 to 15,000 murrelets). In their forested nesting habitats, Marbled Murrelets have lost about 15 percent of their suitable nesting habitat in Southeast Alaska, and 33 to 49 percent in British Columbia, from industrial-scale logging within the past half century. Increased predation also may be a threat to murrelet populations, related to fragmentation and edge effects from logging and development, and recent population increases observed for some important murrelet predators, including Bald Eagles ( Haliaeetus leucocephalus ), Common Ravens ( Corvus corax ), and Steller’s Jays ( Cyanocitta stelleri ). Nesting habitat losses cannot explain the declines observed in areas where industrial logging has not occurred on a large scale (e.g., Prince William Sound) or at all (Glacier Bay). The apparent change in population size and rates of decline reported for the Marbled Murrelet are large, and we therefore considered alternative explanations and precedents for changes of similar magnitude in other marine wildlife populations in the Northeastern Pacific Ocean. The declines are likely real, and related to combined and cumulative effects from climate-related changes in the marine ecosystem (most likely the 1977 regime shift) and human activities (logging, gillnet bycatch, oil pollution). Much uncertainty about the decline could be alleviated by continuing to repeat boat surveys in Prince William Sound and lower Cook Inlet, and by repeating the boat survey of Southeast Alaska that was conducted in 1994. This survey used a statistically sound design and covered the region that has been and likely remains the center of the species’ abundance. Important questions remain to be addressed about methods for measuring population status and change, adult mortality (major sources, density dependence, seasonal concordance), and the movements of wintering populations.

Alaska, British Columbia↗

USGS1995

Double-crested cormorants along the Upper Mississippi River

The Upper Mississippi River is an important habitat corridor for migratory birds and other wildlife, and it supports an important commercial and sport fishery. A study was initiated by the U.S. Fish and Wildlife Service in 1991 to describe Double-crested cormorant (Phalacrocorax auritus) distribution and abundance on the Upper Mississippi River throughout the year to better understand the possible impacts of cormorants on fish resources and populations of other piscivorous birds. Double-crested Cormorants were common breeders and abundant during migration on the Upper Mississippi River during the 1940s. Numbers of cormorants declined in the 1960s and 1970s along the Upper Mississippi River as they did in other parts of the United States. In 1992, 418 cormorant pairs were estimated to have nested in four colonies on the Upper Mississippi River, and less than 7,000 cormorants were estimated to have migrated along the river during the fall and spring of 1991 and 1992. Recent public concern for fish resources has grown with a perceived growth of the local cormorant population. Migrating cormorants collected on the Upper Mississippi River took Gizzard Shad (Dorosoma cepedianum) primarily, but chicks were fed a wide variety of fish species.

Colonial Waterbirds↗

USGS2015

Colonial waterbird predation on Lost River and shortnose suckers based on recoveries of passive integrated transponder tags

We evaluated predation on Lost River suckers ( Deltistes luxatus ) and shortnose suckers ( Chasmistes brevirostris ), both listed under the Endangered Species Act (ESA), from American white pelicans ( Pelecanus erythrorhynchos ) and double-crested cormorants ( Phalacrocorax auritus ) nesting at mixed species colonies on Clear Lake Reservoir, CA and Upper Klamath Lake, OR during 2009-2014. Predation was evaluated by recovering passive integrated transponder (PIT) tags that were implanted in suckers, subsequently consumed by pelicans or cormorants, and deposited on the birds’ nesting colonies. Data from PIT tag recoveries were used to estimate predation rates (proportion of available tagged suckers consumed) by birds to evaluate the relative susceptibility of suckers to avian predation in Upper Klamath Basin. Data on the size of pelican and cormorant colonies (number of breeding adults) at Clear Lake and Upper Klamath Lake were also collected and reported in the context of predation on suckers. Results indicate that predation rates varied by sucker species (Lost River, shortnose), sucker age-class (adult, juvenile), bird colony location (Upper Klamath Lake, Clear Lake), and year (2009-2014), demonstrating that predator-prey interactions in the system were dynamic during the study period. Tagged suckers ranging from 72 mm to 730 mm were susceptible to cormorant or pelican predation; all but the largest of the tagged Lost River suckers were susceptible to avian predation. Estimates of minimum, annual predation rates ranged from <0.1% to 4.6% of the available Lost River suckers and from <0.1% to 4.2% of the available shortnose suckers during the study period. Of the two colony locations evaluated, predation rates on suckers in Clear Lake were generally higher by birds nesting at mixed-species colonies on Clear Lake. Birds nesting on Clear Lake also commuted over 75 kilometers to forage on suckers in Upper Klamath Lake. Conversely, there was no evidence that birds nesting in Upper Klamath Lake foraged on tagged suckers in Clear Lake. Although sample sizes of tagged juvenile suckers were small and limited to fish tagged in Upper Klamath Lake, there was evidence that bird predation on juvenile suckers was higher than on adult suckers, with annual predate rate estimates on juvenile suckers ranging from 5.7% to 8.4% of available fish. The minimum annual predation rates presented here suggests that avian predation may be a factor limiting recovery of populations of Lost River and shortnose suckers, particularly juvenile suckers in Upper Klamath Lake and adult suckers in Clear Lake. Additional research is needed, however, to better assess the impacts of avian predation on sucker populations by (1) recovering PIT tags in a manner so that the species of avian predator is known (i.e., pelican vs. cormorant), (2) measuring predator-specific PIT tag deposition probabilities at each colony, (3) increasing the sample of juvenile suckers in the population that are PIT-tagged, and (4) recovering sufficient sample sizes of PIT tags on bird colonies to describe how various biotic and abiotic factors (e.g., fish size and condition, water levels and quality, and other factors) contribute to sucker susceptibility to avian predation in the Upper Klamath Basin.

California, Oregon↗

USGS2006

Contaminant exposure and potential effects on terrestrial vertebrates residing in the National Capital Region network and Mid-Atlantic network

Part of the mission of the National Park Service is to preserve the natural resources, processes, systems, and associated values of its units in an unimpaired condition. Environmental contamination and pollution processes are well recognized stressors addressed by its management policies and plans. A recent study indicates that contemporary terrestrial vertebrate ecotoxicological data are lacking for 59 of 126 Park Service units located in coastal watersheds exhibiting serious water quality problems or high vulnerability to pollution. Based upon these findings, a more in-depth evaluation of contaminant threats and ecotoxicological data gaps related to terrestrial vertebrates was undertaken at 23 Inventory and Monitoring National Park units in National Capital Region and Mid-Atlantic Networks. Ecotoxicological data were compiled for each park unit through literature searches and meetings with Park Service personnel. Information on contemporary and on persistent legacy pollutants in air, water, soil, and terrestrial vertebrates (amphibians, reptiles, birds and mammals) were evaluated. To identify contaminant threats in proximity to the 23 Park Service study units, data was gathered on National Priority List Superfund sites, Section 303(d) Impaired Waterbodies, the number and relative toxicity of current use pesticides and herbicides, Toxic Release Inventory sites and discharge of priority pollutants, and Fish Consumption Advisories. A metric was derived that described the quality and quantity of existing data for each park, and in combination with known contaminant threats, park units in need of additional study were identified. Results demonstrated that over half of the Park Service study units are near Toxic Release Inventory sites discharging dioxins, polychlorinated biphenyls, lead or mercury into air or water, and fish consumption advisories are in effect at or near 22 of the 23 study units. Pesticide and herbicide use at the park units is minimal, with the exception of those units with significant agricultural leases. Despite highly regulated use, many of the pesticides and herbicides applied are believed to be highly toxic to amphibians, and some of the compounds are also highly toxic to birds. Only 70 reports were found that describe terrestrial vertebrate ecotoxicology data on or near the study units. Of the greater than 75,000 compounds in commerce in the United States, existing terrestrial vertebrate exposure and effects data in the pr esent study were limited to 58 legacy organochlorine pesticides, polychlorinated biphenyls and individual congeners, insecticides and rodenticides, metals, and some contemporary compounds (e.g., polybrominated diphenyl ether flame retardants, and alkylphenol and ethoxylate surfactants). Based upon these and other findings, ecotoxicological monitoring and research investigations of terrestrial vertebrates are warranted at several National Parks. These include Shenandoah National Park, Richmond National Battlefield, Chesapeake & Ohio Canal National Historic Park, Valley Forge National Historic Park, Hopewell Furnace National Historic Site, Monocacy National Battlefield, and Harpers Ferry National Historic Park. The types of investigations vary according to the species present at these parks and potential contaminant threats, but should focus on contemporary use pesticides and herbicides, polychlorinated biphenyls, mercury, lead, and perhaps, emerging contaminants including antibiotics, flame retardants, pharmaceuticals, and surfactants. Other management recommendations include additional training for natural resource staff members in the area of ecotoxicology, inclusion of terrestrial vertebrate contaminant monitoring and the Contaminant Assessment Process (U.S. Geological Survey Biomonitoring of Environmental Status and Trends Project) into the National Park Service Vital Signs Program, development of protocols for hand ling and toxicological analysis of dead or seemingly affected wildlife, consideration of some alternative methods and compounds for pest management and weed control, and use of non-toxic fishing tackle by visitors.

Maryland, Pennsylvania, Virginia↗

USGS2020

Avian community responses to management of vegetation and water levels in restored wetlands at the Humacao Nature Reserve, Puerto Rico

Coastal wetlands of the Caribbean have been greatly reduced in area and quality, and information on wildlife responses to management is lacking. We applied wetland management practices (disking, control of water levels) in a site historically disturbed by Saccharum spp. (sugarcane) cultivation at the Humacao Nature Reserve, southeastern Puerto Rico, and evaluated avian community response. We conducted weekly bird surveys and nest searches on disked and non-disked plots within recently constructed impoundments. The avian community shifted from 16 upland dominated species pre-restoration, to 67 wetland-dependent species at the end of our study (2001–2002). Ordination analysis indicated avian guild use of plots varied with environmental variables. Bird species diversity was not influenced by treatment, month, or salinity levels but was influenced by water depth and vegetation cover. Bird abundance was influenced by water depth, but not by treatment, month, salinity or vegetation cover. Furthermore, water depths of 0.10–0.20 m and salinity of ≤15 ppt promoted habitat conditions suitable for a diverse wetland avian community. We located 268 nests of 8 wetland bird species and observed adults with young of various other waterbirds, including species of conservation concern such as Dendrocygna arborea (West Indian Whistling Duck) and Porzana flaviventer (Yellow-breasted Crake). Bird community responses suggest that management practices (i.e., soil disturbance and control of water levels) can improve wetland biodiversity in abandoned sugarcane fields of Puerto Rico. Moreover, these practices may benefit wetland biodiversity in other Caribbean islands with a similar history of land use and habitat degradation.

Humacao Nature Reserve↗

USGS2022

Toward scoping reviews of individual bird species

Scoping reviews, in which the literature on a given topic is systematically collated and summarized, aid literature searches and highlight knowledge gaps on a given topic, thus hastening scientific progress and informing conservation efforts. Because much research and conservation is targeted at the species level, ornithology and bird conservation would benefit from scoping reviews of individual species. We present and apply a framework for scoping reviews for three disparate raptor species: California Condor Gymnogyps californianus , Harpy Eagle Harpia harpyja and Gyrfalcon Falco rusticolus . We consulted expert panels to develop appropriate search strings and lists of essential literature, i.e. ‘benchmark articles’. We searched Web of Science, Scopus and Google Scholar. Searches for California Condor, Harpy Eagle and Gyrfalcon returned 268, 138 and 343 articles, respectively, that discuss, review or collect empirical data for the focal species. Our searches returned all benchmark articles identified by species experts, indicating that the searches captured the most important work on each species. We coded each study according to the topic addressed, country and month in which data were collected. We also coded threats, stresses and conservation actions addressed by studies, following definitions used by the International Union for the Conservation of Nature (IUCN) during Red List assessments. Literature summaries for each species include the number of studies addressing certain topics, monthly timing of research and global maps of research focus. Our coding scheme revealed important knowledge gaps for each species. Effects of conservation actions on wild individuals were less studied for California Condors. Harpy Eagles were less studied outside of Brazil and Panama, and Gyrfalcons were less studied outside of their breeding season. Scoping reviews of the world's bird species would help to identify critical knowledge gaps, thereby aiding the global effort to assuage the sixth mass extinction.

Ibis↗