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At least 109 records · Page 6Linked to original sources
USGS2024

High inter-population connectivity and occasional gene flow between subspecies improves recovery potential for the endangered Least Bell’s Vireo

Increasingly, genomic data are being used to supplement field-based ecological studies to help evaluate recovery status and trends in endangered species. We collected genomic data to address two related questions regarding the Least Bell’s Vireo ( Vireo bellii ), an endangered migratory songbird restricted to southern California riparian habitat for breeding. First, we sought to delineate the range limits and potential overlap between Least Bell’s Vireo and its sister subspecies, the Arizona Bell’s Vireo, by analyzing samples from the deserts of eastern California, southwestern Nevada, Utah and Arizona. Second, we evaluated genetic structure among Least Bell’s Vireo populations in coastal California and estimated effective population size. Clustering analyses based on 10,571 single nucleotide polymorphisms (SNPs) from 317 samples supported two major groups that aligned closely to the previously defined subspecies ranges. The first cluster included birds in the Central Valley, all coastal drainages, and westernmost deserts of California, with no further sub-structuring among coastal drainages. Almost all birds from the Amargosa River in eastern California and eastward assigned to the second cluster; however, low levels of gene flow were detected across the subspecies groups, with greater rates of gene flow from Arizona Bell’s Vireo to Least Bell’s Vireo than the reverse. Admixed individuals occurred in the California deserts; and although smaller than coastal populations, desert populations may be important for maintaining and replenishing genetic diversity and facilitating the movement of potentially adaptive genes between subspecies. Within Least Bell’s Vireo, local populations in coastal drainages comprised a single genetic population, with some evidence of close relatives distributed across drainages, suggesting these could function as a well-connected metapopulation. These results are consistent with previous Least Bell’s Vireo banding studies that reported high rates of dispersal among drainages. Effective population size for both subspecies was high, suggesting that adaptive potential has been maintained despite previous declines.

Ornithological Applications↗
USGS2025

Shortening migration by 4500 km does not affect nesting phenology or increase nest success for black brant (Branta bernicla nigricans) breeding in Arctic and subarctic Alaska

Background Since the 1980s, Pacific Black Brant ( Branta bernicla nigricans , hereafter brant) have shifted their winter distribution northward from Mexico to Alaska (approximately 4500 km) with changes in climate. Alongside this shift, the primary breeding population of brant has declined. To understand the population-level implications of the changing migration strategy of brant, it is important to connect movement and demographic data. Our objectives were to calculate migratory connectivity, a measure of spatial and temporal overlap during the non-breeding period, for Arctic and subarctic breeding populations of brant, and to determine if variation in migration strategies affected nesting phenology and nest survival. Methods We derived a migratory network using light-level geolocator migration tracks from an Arctic site (Colville River Delta) and a subarctic site (Tutakoke River) in Alaska. Using this network, we quantified the migratory connectivity of the two populations during the winter. We also compared nest success rates among brant that used different combinations of winter sites and breeding sites. Results The two breeding populations were well mixed during the winter, as indicated by a migratory connectivity score close to 0 (− 0.06) at the primary wintering sites of Izembek Lagoon, Alaska (n = 11 brant) and Baja California, Mexico (n = 48). However, Arctic birds were more likely to migrate the shorter distance to Izembek (transition probability = 0.24) compared to subarctic birds (transition probability = 0.09). Nest survival for both breeding populations was relatively high (0.88–0.92), and we did not detect an effect of wintering site on nest success the following year. Conclusions Nest survival of brant did not differ among brant that used wintering sites despite a 4500 km difference in migration distances. Our results also suggested that the growing Arctic breeding population is unlikely to compensate for declines in the larger breeding population of brant in the subarctic. However, this study took place in 2011–2014 and wintering at Izembek Lagoon may have greater implications for reproductive success under future climate conditions.

Movement Ecology↗
USGS1975

California condor plumage and molt as field study aids

An analysis is made of the reliability of plumage and molt characteristics of the California condor for estimating age and identifying individual birds. Neither character seems sufficiently reliable to use in more than a general way.

California Fish and Game↗
USGS2008

At-sea distribution of radio-marked Ashy Storm-Petrels Oceanodroma homochroa captured on the California Channel Islands

Small, rare and wide-ranging pelagic birds are difficult to locate and observe at sea; little is therefore known regarding individual movements and habitat affinities among many of the world's storm-petrels (Family Hydrobatidae). We re-located 57 of 70 radio-marked Ashy Storm-Petrels Oceanodroma homochroa captured at three colonies in the California Channel Islands: Scorpion Rocks (2004, 2005), Santa Barbara Island (2004) and Prince Island (2005). Between 23 July and 22 September 2004, and 5 July and 4 August 2005, we flew 29 telemetry surveys, covered more than 65 000 km2 (2004) and 43 000 km2 (2005) of open ocean from San Nicolas Island north to the Farallon Islands and obtained 215 locations from 57 storm-petrels at sea. In both years, radio-marked storm-petrels were aggregated over the continental slope from Point Conception to Point Buchon, within the western Santa Barbara Channel, and over the Santa Cruz Basin between Santa Cruz, San Nicolas and Santa Barbara islands. Individuals captured in the Channel Islands ranged more than 600 km and were located as far north as Gulf of the Farallones National Marine Sanctuary. This is the first study to use radiotelemetry to determine the at-sea distribution and movements for any storm-petrel species.

Marine Ornithology: Journal of Seabird Research an↗
USGS2016

Mortality monitoring design for utility-scale solar power facilities

Introduction Solar power represents an important and rapidly expanding component of the renewable energy portfolio of the United States (Lovich and Ennen, 2011; Hernandez and others, 2014). Understanding the impacts of renewable energy development on wildlife is a priority for the U.S. Fish and Wildlife Service (FWS) in compliance with Department of Interior Order No. 3285 (U.S. Department of the Interior, 2009) to “develop best management practices for renewable energy and transmission projects on the public lands to ensure the most environmentally responsible development and delivery of renewable energy.” Recent studies examining effects of renewable energy development on mortality of migratory birds have primarily focused on wind energy (California Energy Commission and California Department of Fish and Game, 2007), and in 2012 the FWS published guidance for addressing wildlife conservation concerns at all stages of land-based wind energy development (U.S. Fish and Wildlife Service, 2012). As yet, no similar guidelines exist for solar development, and no published studies have directly addressed the methodology needed to accurately estimate mortality of birds and bats at solar facilities. In the absence of such guidelines, ad hoc methodologies applied to solar energy projects may lead to estimates of wildlife mortality rates that are insufficiently accurate and precise to meaningfully inform conversations regarding unintended consequences of this energy source and management decisions to mitigate impacts. Although significant advances in monitoring protocols for wind facilities have been made in recent years, there remains a need to provide consistent guidance and study design to quantify mortality of bats, and resident and migrating birds at solar power facilities (Walston and others, 2015). In this document, we suggest methods for mortality monitoring at solar facilities that are based on current methods used at wind power facilities but adapted for the unique conditions encountered at solar facilities. In particular, unlike at wind-power facilities, the unimpeded access to almost all areas within the facilities, the typically flat terrain, and general absence of thick vegetation allow distance-sampling techniques (Buckland and others, 2001, 2004) to be exploited to advantage at industrial solar sites. These protocols build on the work of Nicolai and others (2011), and as our understanding and techniques for monitoring improve, the methods may be further modified to incorporate improvements in the future. We present case studies based on monitoring methods currently implemented at different utility-scale solar facilities to illustrate how distance-sampling techniques may improve overall detectability without substantially increasing costs. Every facility is unique, and the protocols presented may be adapted based on specific monitoring objectives and conditions at each site. We provide guidance for designing monitoring programs whose objective it is to estimate the total number of bird and bat fatalities occurring at a facility over an extended period of time. We address spatial variation in causes of mortality, as well as potential sources of imperfect detection, for example, animals falling in or moving to unsearched areas, carcasses removed by predators, and carcasses missed by searchers. We suggest methods to estimate and account for each source of imperfect detection. This document focuses on monitoring design only and does not discuss approaches for estimating mortality from collected data. The development of statistically sound estimators relevant to the solar context is a current topic of research, although there are already strong foundations for estimation with distance-sampling methods in similar open, arid environments (Anderson and others, 2001; Freilich and others, 2005). Nonetheless, if protocols described in this document are followed, the resulting data will be adequate and sufficient for estimating mortality using newly formulated estimators.

Open-File Report↗
USGS1995

California condors

The California condor ( Gymnogyps californianus ) is a member of the vulture family. With a wingspan of about 3 m (9 ft) and weighing about 9 kg (20 lb), it spends much of its time in soaring flight visually seeking dead animals as food. The California condor has always been rare (Wilbur 1978; Pattee and Wilbur 1989). Although probably numbering in the thousands during the Pleistocene epoch in North America, its numbers likely declined dramatically with the extinction of most of North America's large mammals 10,000 years ago. Condors probably numbered in the hundreds and were nesting residents in British Columbia, Washington, Oregon, California, and Baja California around 1800. In 1939 the condor population was estimated at 60-100 birds, and its home range was reduced to the mountains and foothills of California, south of San Francisco and north of Los Angeles. Conservation to halt the condor's decline included establishing the Sisquoc (1937) and Sespe (1947) condor sanctuaries within the Los Padres National Forest, obtaining fully protected status under California Fish and Game Code (1953), placement on California's first state endangered species list (1971), and, finally, being listed by the federal government under the Endangered Species Act of 1973 (Wilbur 1978). The success of these efforts could not be judged, however, because verifiable status and trends data did not become available until 1982. By using these data, we confirmed the decline in condor numbers over the past 50 years was even greater than thought.

Book chapter↗
USGS2025

Survival of captive-raised light-footed Ridgway’s rails is influenced by release date and time in wild

Captive breeding and translocation programs are an increasingly common conservation tool and management strategy used for some of the rarest and most endangered species in the world. These programs come at a high cost, and many translocation programs fail to monitor animals after release. Light-footed Ridgway’s rails ( Rallus obsoletus levipes ) are federally endangered marsh birds endemic to coastal wetlands of southern California and northern Mexico. Juvenile captive-raised light-footed Ridgway’s rails have been released into marshes within their U.S. range for >20 yr, but little effort has been devoted to post-release tracking of their movement and survival. We used satellite GPS transmitters to track survival of 46 juvenile captive-released and 42 juvenile wild-caught light-footed Ridgway’s rails from 2020–2022. Our results suggest that juvenile captive-released rails had lower initial daily survival probability (0.979) compared with that of juvenile wild-caught rails (0.994). Survival probability of captive-released rails increased with time in the wild, matching that of wild birds at about 100 d post-release. Survival of captive-released birds was most influenced by the date birds were released (releases in early summer had the highest survival). Our study emphasizes the importance of post-release monitoring as part of any captive breeding and translocation program and provides important insight into management strategies that may improve captive-released rail survival in the wild.

California↗
USGS2021

Modeling Least Bell’s Vireo habitat suitability in current and historic ranges in California

We developed a habitat suitability model for the federally endangered Least Bell’s Vireo ( Vireo bellii pusillus ) across its current and historic range in California. The vireo disappeared from most of its range by the 1980s, remaining only in southern California and northern Baja California, Mexico. This decline was due to habitat loss and introduction of brood parasitic brown-headed cowbirds ( Molothrus ater ) into California in the late 1800s. Habitat protection and management since the mid-1980s increased southern California vireo populations with small numbers of birds recently expanding back into the historic range. The vireo habitat model will help meet the U.S. Fish and Wildlife Service recovery objectives by distinguishing specific areas to survey for new occurrences; characterizing important vireo-habitat relationships; and identifying areas for habitat management. We constructed models based on the vireo’s current range to predict suitable habitat in the historic range, which differs substantially in environmental conditions. We used the partitioned Mahalanobis D 2 modeling technique designed to predict habitat suitability in areas not included in a sample of species locations and under novel conditions. We constructed alternative models with different combinations of environmental variables hypothesized to be important components of vireo habitat. We selected a set of best performing models to predict suitable habitat for a riparian vegetation grid buffered 500 meters across California. Most models for southern California did not predict suitable habitat in the historic range. The top performing model has an area under the curve value of 0.93. It is a simple model and discriminated among riparian habitats, with only 6 percent predicted as suitable. On average, suitable vireo habitat had more than 60-percent riparian vegetation and flat land at the 150-meter scale, little-to-no slope, and was within 130 meters of water.

California↗
USGS2009

The reintroduction of the Andean condor into Colombia, South America: 1989-1991

From 1989 to 1991,22 captive-reared Andean condors Vultur gryphus were released into three protected areas in the Andes of Colombia, South America. The goals of this reintroduction programme were to re-establish populations of these birds in protected habitat where the species had been extirpated, and to train local biologists in the conservation techniques necessary to recover their native condor. All birds were hatched, reared and released according to the protocols established by the US Fish and Wildlife Service and the California Department of Fish and Game for the California condor Gymnogyps californianus. At the time of release, the birds ranged in age from 11 to 26 months. Each bird was fitted with individually numbered wing tags and wing-mounted radio transmitters. Of the 22 released animals, 19 currently survive – a substantial increase to the wild population in Colombia, which had been estimated by Colombian biologists to number only 20 individuals.

Oryx↗
USGS2024

Eggshell thickness and egg morphometrics in five songbird species from the Central Valley, California

Avian eggshell thickness is an important life history metric in birds and has broad applications across disciplines ranging from animal behavior to toxicology. Empirical eggshell thickness values for songbirds (Order Passeriformes) are under-represented in the literature due to the difficulty of measuring smaller eggs using traditional methods. We used a Hall-effect thickness gauge to measure eggs of five focal songbird species from California’s Central Valley: House Wren ( Troglodytes aedon ; n = 567), Tree Swallow ( Tachycineta bicolor ; n = 297), Ash-throated Flycatcher ( Myiarchus cinerascens ; n = 21), Western Bluebird ( Sialia mexicana ; n = 13), and Bewick’s Wren ( Thryomanes bewickii ; n = 5). We compared minimum eggshell thickness measurements at the equator and sharp pole, and we related eggshell thickness to other egg morphometrics and adult body mass. Eggshell thickness at the equator was 5.6% thicker in Ash-throated Flycatchers and 3.5% thinner in Tree Swallows compared with eggshell thickness at the sharp pole. Among species, eggshell thickness at the sharp pole was greater in species with larger eggs, whereas, within species, larger eggs were thinner at the sharp pole. Eggshells were 8% and 11% thinner in late incubation eggs (≥75% of total incubation duration) than early incubation (≤10% of total incubation duration) for House Wren and Tree Swallow eggs, respectively. Whenever possible, it is preferable to use empirical eggshell thickness data that are specific to the species and geographic region being studied, and a relatively new method used in this study allows accurate measurement of small eggs without having to compromise the integrity of preserved eggshell specimens.

Journal of Field Ornithology↗
USGS2017

Lack of observed movement response to lead exposure of California condors

Lead poisoning is an important conservation concern for wildlife, and scavenging birds are especially at risk from consumption of carcasses of animals killed with lead ammunition. Because current methods to identify lead exposure require animal capture and blood collection, management would benefit from the development of a less costly and noninvasive behavioral test for illness in wild animals. We attempted to design such a test to identify lead exposure in California condors ( Gymnogyps californianus ) that we tracked with global positioning system (GPS) telemetry in southern California, USA, 2013–2016. We measured blood-lead concentrations in tracked birds and expected that flight behavior would be influenced by lead exposure; thus, we measured the effect of blood-lead concentrations on 2 different types of movement rates and on the proportion of time condors spent in flight. We found no effect of lead exposure on any of these 3 behavioral metrics. Our work suggests that the measurements we took of flight behaviors were not a useful tool in predicting lead exposure in the mildly to moderately exposed birds we studied. Wild birds are effective at hiding illness, especially condors who have a strong social hierarchy in which showing weakness is a disadvantage. However, focusing on behaviors other than flight, expanding the sample studied to include birds with a wider range of lead concentration values, or analyzing tissues such as feathers (rather than, or in addition to, blood) may be more useful for identification of lead exposure and other diseases that may limit wildlife populations. © 2017 This article is a U.S. Government work and is in the public domain in the USA.

Journal of Wildlife Management↗
USGS2009

Lead poisoning in wild birds

Lead in its various forms has been used for thousands of years, originally in cooking utensils and glazes and more recently in many industrial and commercial applications. However, lead is a potent, potentially deadly toxin that damages many organs in the body and can affect all animals, including humans. By the mid 1990s, lead had been removed from many products in the United States, such as paint and fuel, but it is still commonly used in ammunition for hunting upland game birds, small mammals, and large game animals, as well as in fishing tackle. Wild birds, such as mourning doves, bald eagles, California condors, and loons, can die from the ingestion of one lead shot, bullet fragment, or sinker. According to a recent study on loon mortality, nearly half of adult loons found sick or dead during the breeding season in New England were diagnosed with confirmed or suspected lead poisoning from ingestion of lead fishing weights. Recent regulations in some states have restricted the use of lead ammunition on certain upland game hunting areas, as well as lead fishing tackle in areas frequented by common loons and trumpeter swans. A variety of alternatives to lead are available for use in hunting, shooting sports, and fishing activities.

Fact Sheet↗
USGS2022

Vulnerability of avian populations to renewable energy production

Renewable energy production can kill individual birds, but little is known about how it affects avian populations. We assessed the vulnerability of populations for 23 priority bird species killed at wind and solar facilities in California, USA. Bayesian hierarchical models suggested that 48% of these species were vulnerable to population-level effects from added fatalities caused by renewables and other sources. Effects of renewables extended far beyond the location of energy production to impact bird populations in distant regions across continental migration networks. Populations of species associated with grasslands where turbines were located were most vulnerable to wind. Populations of nocturnal migrant species were most vulnerable to solar, despite not typically being associated with deserts where the solar facilities we evaluated were located. Our findings indicate that addressing declines of North American bird populations requires consideration of the effects of renewables and other anthropogenic threats on both nearby and distant populations of vulnerable species.

California↗
USGS2022

Collateral damage: Anticoagulant rodenticides pose threats to California condors

Anticoagulant rodenticides (ARs) are widespread environmental contaminants that pose risks to scavenging birds because they routinely occur within their prey and can cause secondary poisoning. However, little is known about AR exposure in one of the rarest avian scavengers in the world, the California condor ( Gymnogyps californianus ). We assessed AR exposure in California condors and surrogate turkey vultures ( Cathartes aura ) to gauge potential hazard to a proposed future condor flock by determining how application rate and environmental factors influence exposure. Additionally, we examined whether ARs might be correlated with prolonged blood clotting time and potential mortality in condors. Only second-generation ARs (SGARs) were detected, and exposure was detected in all condor flocks. Liver AR residues were detected in 42% of the condors (27 of 65) and 93% of the turkey vultures (66 of 71). Although concentrations were generally low (<10 ng/g ww), 48% of the California condors and 64% of the turkey vultures exposed to ARs exceeded the 5% probability of exhibiting signs of toxicosis (>20 ng/g ww), and 10% and 13% exceeded the 20% probability of exhibiting signs toxicosis (>80 ng/g ww). There was evidence of prolonged blood clotting time in 16% of the free-flying condors. For condors, there was a relationship between the interaction of AR exposure index (legal use across regions where condors existed) and precipitation, and the probability of detecting ARs in liver. Exposure to ARs may complicate recovery efforts of condor populations within their current range and in the soon to be established northern California experimental population. Continued monitoring of AR exposure using plasma blood clotting assays and residue analysis would allow for an improved understanding of their hazard to condors, particularly if paired with recent movement data that could elucidate exposure sources on the landscape occupied by this endangered species.

California↗
USGS2016

Nuclear and mitochondrial DNA analyses of golden eagles (Aquila chrysaetos canadensis) from three areas in western North America; initial results and conservation implications

Understanding the genetics of a population is a critical component of developing conservation strategies. We used archived tissue samples from golden eagles ( Aquila chrysaetos canadensis ) in three geographic regions of western North America to conduct a preliminary study of the genetics of the North American subspecies, and to provide data for United States Fish and Wildlife Service (USFWS) decision-making for golden eagle management. We used a combination of mitochondrial DNA (mtDNA) D-loop sequences and 16 nuclear DNA (nDNA) microsatellite loci to investigate the extent of gene flow among our sampling areas in Idaho, California and Alaska and to determine if we could distinguish birds from the different geographic regions based on their genetic profiles. Our results indicate high genetic diversity, low genetic structure and high connectivity. Nuclear DNA Fst values between Idaho and California were low but significantly different from zero (0.026). Bayesian clustering methods indicated a single population, and we were unable to distinguish summer breeding residents from different regions. Results of the mtDNA AMOVA showed that most of the haplotype variation (97%) was within the geographic populations while 3% variation was partitioned among them. One haplotype was common to all three areas. One region-specific haplotype was detected in California and one in Idaho, but additional sampling is required to determine if these haplotypes are unique to those geographic areas or a sampling artifact. We discuss potential sources of the high gene flow for this species including natal and breeding dispersal, floaters, and changes in migratory behavior as a result of environmental factors such as climate change and habitat alteration. Our preliminary findings can help inform the USFWS in development of golden eagle management strategies and provide a basis for additional research into the complex dynamics of the North American subspecies.

Alaska, California, Idaho, Oregon↗