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Todd E. Katzner

Publications and source records attributed to Todd E. Katzner.

At least 109 records · Page 6Linked to original sources
USGS2019

Lead exposure of red-shouldered hawks during the breeding season in the central Appalachians, USA

Lead is toxic to humans and wildlife. Most studies of lead exposure of raptors focus on the winter, non-breeding season when they scavenge heavily. We evaluated blood lead concentrations (BLCs) of red-shouldered hawks (Buteo lineatus) during the non-scavenging season in the eastern United States. BLCs of 53 of 70 hawks were above the limit of detection ( x¯ = 9.25 µg/dL ± 19.81; ± SD). Adult hawks had higher BLCs ( x¯ = 12.86 µg/dL ± 24.72) than did nestlings ( x¯ = 3.25 µg/dL ± 2.62; p ≤ 0.001, χ2 = 13.2). There was no difference in BLCs of adult hawks among physiographic provinces but there were differences between urban and non-urban settings (p = 0.04, χ2 = 4.2). Soils and invertebrate hawk prey also had quantifiable lead concentrations. Our work shows that red-shouldered hawks are exposed to lead when not scavenging, and suggests pathways by which these birds may be exposed.

Central Appalachians↗
USGS2019

Relevance of individual and environmental drivers of movement of Golden Eagles

An animal's movement is expected to be governed by an interplay between goals determined by its internal state and energetic costs associated with navigating through the external environment. Understanding this ecological process is challenging when an animal moves in two dimensions and even more difficult for birds that move in a third dimension. To understand the dynamic interaction between the internal state of an animal and the variable external environment, we evaluated hypotheses explaining association of different covariates of movement and the trade‐offs birds face as they make behavioural decisions in a fluctuating landscape. We used ~870 000 GPS telemetry data points collected from 68 Golden Eagles Aquila chrysaetos to test demographic, diel, topographic and meteorological hypotheses to determine (1) the probability that these birds would be in motion and (2), once in motion, their flight speed. A complex and sometimes interacting set of potential internal and external factors determined movement behaviour. There was good evidence that reproductive state, manifested as age, sex and seasonal effects, had a significant influence on the probability of being in motion and, to a lesser extent, on speed of motion. Likewise, movement responses to the external environment were often unexpectedly strong. These responses, to northness of slope, strength of orographic updraft and intensity of solar radiation, were regionally and temporally variable. In contrast to previous work showing the role of a single environmental factor in determining movement decisions, our analyses support the hypothesis that multiple factors simultaneously interact to influence animal movement. In particular they highlighted how movement is influenced by the interaction between the individual's internal reproductive state and the external environment, and that, of the environmental factors, topographic influences are often more relevant than meteorological influences in determining patterns of flight behaviour. Further disentangling of how these internal and externals states jointly affect movement will provide additional insights into the energetic costs of movement and benefits associated with achieving process‐driven goals.

California↗
USGS2019

Elevated heterozygosity in adults relative to juveniles provides evidence of viability selection on eagles and falcons

Viability selection yields adult populations that are more genetically variable than those of juveniles, producing a positive correlation between heterozygosity and survival. Viability selection could be the result of decreased heterozygosity across many loci in inbred individuals and a subsequent decrease in survivorship resulting from the expression of the deleterious alleles. Alternatively, locus-specific differences in genetic variability between adults and juveniles may be driven by forms of balancing selection, including heterozygote advantage, frequency-dependent selection, or selection across temporal and spatial scales. We use a pooled-sequencing approach to compare genome-wide and locus-specific genetic variability between 74 golden eagle ( Aquila chrysaetos ), 62 imperial eagle ( Aquila heliaca ), and 69 prairie falcon ( Falco mexicanus ) juveniles and adults. Although genome-wide genetic variability is comparable between juvenile and adult golden eagles and prairie falcons, imperial eagle adults are significantly more heterozygous than juveniles. This evidence of viability selection may stem from a relatively smaller imperial eagle effective population size and potentially greater genetic load. We additionally identify ~2000 single-nucleotide polymorphisms across the 3 species with extreme differences in heterozygosity between juveniles and adults. Many of these markers are associated with genes implicated in immune function or olfaction. These loci represent potential targets for studies of how heterozygote advantage, frequency-dependent selection, and selection over spatial and temporal scales influence survivorship in avian species. Overall, our genome-wide data extend previous studies that used allozyme or microsatellite markers and indicate that viability selection may be a more common evolutionary phenomenon than often appreciated.

Journal of Heredity↗
USGS2019

Topographic drivers of flight altitude over large spatial and temporal scales

Bird movements vary spatially and temporally, but the primary drivers that explain such variation can be difficult to identify. For example, it is well known that the availability of updraft influences soaring flight and that topography interacts with weather to produce these updrafts. However, the influences of topography on flight are not well understood. We determined how topographic characteristics influenced flight altitude above ground level (AGL) of a large soaring bird, the Golden Eagle (Aquila chrysaetos), over several regions within the State of California, USA. Primary drivers of flight AGL, those to which eagles showed the same response at all spatial scales, were topographic roughness, ground elevation and the east-west component of aspect (eastness). Each of these is related to formation of thermal updrafts. Secondary drivers, those to which eagles showed region-specific patterns, included topographic position, percent slope, and the north-south component of aspect (northness). In contrast to primary drivers, these secondary drivers were related to formation of both thermal and orographic updrafts. Overall, drivers of flight altitudes that were related to thermal updrafts showed different levels of complexity due to spatial and temporal variation of those drivers than did flight altitudes related to orographic updrafts.

California↗
USGS2019

Movements of immature bald eagles: Implications for bird aircraft strike hazard

Bald eagle (Haliaeetus leucocephalus) aircraft strikes have increased dramatically over the last 20 years as their populations have recovered to near historic sizes. Their attraction to airfields and their large body size makes them a danger to aircraft and therefore important to airfield wildlife managers. However, their management is complicated by their special protected status and the iconic place they hold in the eyes of the public. To help airfield wildlife managers plan monitoring efforts and make informed management decisions, we studied the movements of 32 bald eagles telemetered as nestlings in the Chesapeake Bay of Virginia, USA. Managers often need to know when fledged eagles are most likely to move enough to encounter airfields near nests. As fledglings aged they moved progressively farther from the nest and spent more time away from the nest. Twenty-eight days after fledging, eagles spent most of the day (81±10%, 95% confidence interval) near the nest (<500 m) and only 7±7% of the daytime away from the nest (>1 km). By day 53 fledglings ventured beyond 2.5 km from the nest and spent 30 ± 15% the day >1 km away from their nest. However, distances moved were influenced by proximity of the nest to water, the quality and salinity of that water, and human population density. Eagles left their natal areas and generally migrated out of the Chesapeake Bay 60.5 ± 7.7 days (4 August) after fledging and returned to the Chesapeake Bay approximately 225 days later (March-April). Eighty-four percent (27 of 32) of the eagles that we tracked encountered 164 airfields across the east coast with 91% of those airfields located within 10 km of the Chesapeake Bay. Encounters with airfields outside the Chesapeake Bay occurred mainly during the first 1.5 years of life, peaking in late fall and early spring. Eagles were recorded on Chesapeake Bay airfields during each year, but encounters peaked in April of the first year of the bird’s life. This month coincides with the height of reported strikes of eagles by aircraft in the region. Our results suggest that eagles fledging from the Chesapeake Bay are not only an issue for airports near the Chesapeake Bay, but for airports across the east coast. Given the continued growth of the population, this issue is likely to continue and grow in significance.

Virginia↗
USGS2019

Lead in piscivorous raptors during breeding season in the Chesapeake Bay region of Maryland and Virginia, USA

Sources of lead exposure of many bird species are poorly understood. We analyzed blood lead concentrations from osprey (n = 244; Pandion haliaetus ) and bald eagles (n = 68; Haliaeetus leucocephalus ) and documented potential sources of lead they may encounter. Adult bald eagles had higher blood lead concentrations than did adult osprey. However, blood lead concentrations of nestlings were similar for both species. Although 62% of osprey had detectable lead concentrations (x ̅ = 1.99 µg/dL ± 4.02; mean; ± SD), there was no difference in the detection frequency or lead concentrations between osprey adults and nestlings. Likewise, we found no differences in the detection frequency or lead concentrations in osprey adults and nestlings from high and low salinity areas. Of the bald eagle samples tested, 55% had detectable lead levels (x ̅ = 6.23 µg/dL ± 10.74). Adult bald eagles had more detectable and higher lead concentrations than did nestlings or pre-adults. Among environmental samples, paint had the highest lead concentrations, followed by sediment, blue catfish ( Ictalurus furcatus ), and gizzard shad ( Dorosoma cepedianum ). There was no correlation between blood lead concentrations of osprey adults and their offspring. Our work indicates that, in the Chesapeake Bay region, there are multiple sources by which piscivorous raptors may be exposed to lead.

Maryland, Virginia↗
USGS2019

Removal of cattle grazing correlates with increases in vegetation productivity and in abundance of imperiled breeding birds

Livestock grazing is the most prevalent land use practice in the western United States and a widespread cause of degradation of riparian vegetation. Riparian areas provide high-quality habitat for many species of declining migratory breeding birds. We analyzed changes in vegetation and bird abundance at a wildlife refuge in southeastern Oregon over 24 years, following cessation of 120 years of livestock grazing. We quantified long-term changes in overall avian abundance and species richness and, specifically, in the abundances of 20 focal species. We then compared the local responses of the focal species to population-scale trends of the same species at three different large spatial scales. Overall avian abundance increased 23% during the 12 years after removal and remained consistent from then through year 24. Three times as many species colonized the survey sites as dropped out. Of the focal species, most riparian woodland-tree or shrub dependent, sagebrush obligate, and grassland or meadow taxa increased in abundance or remained stable locally. As these species were generally of conservation concern, the population increases contradicted regionally declining or stable trends. In contrast, most riparian woodland-cavity nester species decreased in abundance locally, reflecting disruption of aspen stand dynamics by decades of grazing. Avian nest parasites and competitors of native species declined in abundance locally, matching regional trends. Restoring riparian ecosystems by removing livestock appeared to be beneficial to the conservation of many of these declining populations of migratory birds.

Oregon↗
USGS2019

Characteristics of feeding sites of California Condors (Gymnogyps californianus) in the human-dominated landscape of Southern California

Wildlife conservation is often improved by understanding the movement ecology of species and adapting management strategies to dynamic conditions associated with movement. Despite a remarkable recovery over the past 30 year, the establishment of self-sustaining populations of California Condors (Gymnogyps californianus) has been challenging in the human-dominated landscapes of southern California. Among these challenges are those imposed by condor ground-foraging behavior that exposes them to environmental contamination. These include lead poisoning from the ingestion of spent ammunition and micro-trash ingestion and, during takeoff and landing, collisions with human structures. We tracked 28 California Condors for 24 months with patagially mounted GPS telemetry units to investigate the characteristics of ground sites condors visited and to identify spatiotemporal trends that might aid in conservation of this critically endangered species. Ground sites occurred on a wide variety of land cover types, primarily on steep slopes, and those more frequently used were associated with open cover. Condors concentrated their visits to ground sites around a 3 h period near midday, and usage increased from winter to late summer. Our study is the first to use remotely sensed telemetry data to describe fine-scale ecological correlates of condor ground-foraging ecology and therefore has important relevance for ongoing conservation and management strategies for this species. The descriptions of ground sites we provide can be used to target conservation or management actions.

California↗
USGS2019

Roost- and perch-site selection by Golden Eagles (Aquila chrysaetos) in eastern North America

Birds select critical resources to meet needs that vary in response to spatial, temporal, and individual variation. As an example, perch or roost sites may be at locations that provide protection from predators, mobbing, or inclement weather. Applied to large, soaring predators, this theory suggests that they may select perch and roost sites near food resources or at sites where environmental updrafts develop. To test these theories, we characterized selection of nonflight locations throughout the annual cycle for Golden Eagles ( Aquila chrysaetos ) in eastern North America. We determined factors associated with selection of perching (daytime) and roosting (nighttime) sites by eagles by comparing land cover and topographic characteristics of GPS telemetry locations for eagles (used) with random (available) locations. We separately assessed selection for perch and roost sites during each of 4 seasons (winter, summer, and spring and fall migration). Golden Eagles showed different selection patterns for perching by season and age. Throughout the year, eagles selected perch sites on steep slopes. The direction these slopes faced differed among seasons, with eagles selecting south-facing slopes in summer and east-facing slopes during migration. Adults showed greater preferences for broadleaf forests in summer and for ridges in fall. Patterns of perch-site use were consistent with selection for sites that provide thermal protection and access to thermal updrafts. We found few patterns of selection for roosting sites. Our analysis provides insight into decision-making by a longdistance migrant across its annual cycle and throughout its geographic range, and thus into how resource selection changes seasonally.

Wilson Journal of Ornithology↗
USGS2019

Non-anthropogenic diet-based oiling of predatory birds

Oiling of wildlife can have important consequences to individual animals and populations (Kingston 2002). Individual birds that are heavily oiled lose their ability to fly and may become ill or die from hypothermia, starvation, exhaustion, or drowning (Clark 1984, Rocke 1999). For example, large-scale oiling from the Exxon Valdez spill caused local declines in populations of many avian taxa (Irons et al. 2000). Although most oiling reports involve marine wildlife exposed to oil leaked from vessels or oil rigs, oiling also can occur in terrestrial environments, for example, via birds drinking water in puddles on asphalt roadways (Clark and Gorney 1987) or landing in oil field wastewater disposal facilities (Trail 2006, Ramírez 2010).

Journal of Raptor Research↗
USGS2019

An improved mechanical owl for efficient capture of nesting raptors

Scientific study of raptors often requires the use of a lure to capture individuals for marking or collecting various data and samples. Live lure owls in the genus Bubo are commonly used with mist nets or dho-gazas to trap nesting raptors, but the use of these live lures presents ethical, logistical, and financial challenges. Although owls mounted by taxidermists and mechanical owls have been used in place of a live bird, the success of these types of lures varies widely. We created a more realistic mechanical owl with a greater range of motion than previous models, and then tested the owl on six raptor species in a variety of habitats. For all but one species, capture rates using our mechanical owl were similar to or slightly higher than those reported in studies using live lure owls or previously designed mechanical owls. Time to capture of Northern Goshawks ( Accipiter gentilis ) was, on average, 8 min faster when using our mechanical owl compared to a live owl. Cost analysis revealed that both the initial expense and long-term maintenance of a mechanical owl were less than that of a live lure owl. Mechanical owls can be a useful tool for capturing raptors. Although there are some drawbacks to using a mechanical owl, our results suggest that mechanical birds are comparable to live lure owls and we believe the benefits of using a mechanical owl often outweigh the costs.

Journal of Raptor Research↗
USGS2018

Quantitative acoustic differentiation of cryptic species illustrated with King and Clapper rails

Reliable species identification is vital for survey and monitoring programs. Recently, the development of digital technology for recording and analyzing vocalizations has assisted in acoustic surveying for cryptic, rare, or elusive species. However, the quantitative tools that exist for species differentiation are still being refined. Using vocalizations recorded in the course of ecological studies of a King Rail ( Rallus elegans ) and a Clapper Rail ( Rallus crepitans ) population, we assessed the accuracy and effectiveness of three parametric (logistic regression, discriminant function analysis, quadratic discriminant function analysis) and six nonparametric (support vector machine, CART, Random Forest, k ‐nearest neighbor, weighted k ‐nearest neighbor, and neural networks) statistical classification methods for differentiating these species by their kek mating call. We identified 480 kek notes of each species and quantitatively characterized them with five standardized acoustic parameters. Overall, nonparametric classification methods outperformed parametric classification methods for species differentiation (nonparametric tools were between 57% and 81% accurate, parametric tools were between 57% and 60% accurate). Of the nine classification methods, Random Forest was the most accurate and precise, resulting in 81.1% correct classification of kek notes to species. This suggests that the mating calls of these sister species are likely difficult for human observers to tell apart. However, it also implies that appropriate statistical tools may allow reasonable species‐level classification accuracy of recorded calls and provide an alternative to species classification where other capture‐ or genotype‐based survey techniques are not possible.

Ecology and Evolution↗
USGS2018

Effect of heat and singeing on stable hydrogen isotope ratios of bird feathers and implications for their use in determining geographic origin

Rationale Stable hydrogen isotope ( δ 2 H) ratios of animal tissues are useful for assessing movement and geographic origin of mobile organisms. However, it is uncertain whether heat and singeing affects feather δ 2 H values and thus subsequent geographic assignments. This is relevant for birds of conservation interest that are burned and killed at concentrating solar‐energy facilities that reflect sunlight to a receiving tower and generate a solar flux field. Methods We used a controlled experiment to test the effect of known heat loads (exposure to 200, 250 or 300°C for 1 min) on the morphology and δ 2 H values of feathers from two songbird species. Subsequently, we examined the effects of singeing on δ 2 H values of feathers from three other songbird species that were found dead in the field at a concentrating solar‐energy facility. Results Relative to control samples, heating caused visual morphological changes to feathers, including shriveling at 250°C and charring at 300°C. The δ 2 H values significantly declined by a mean of 27.8‰ in experimental samples exposed to 300°C. There was no statistically detectable difference between δ 2 H values of the singed and unsinged portions of field‐collected feathers from the same bird. Conclusions Limited singeing that did not dramatically alter the feather morphology did not substantially affect δ 2 H values of feathers from these songbirds. However, higher temperatures induced charring and reduced δ 2 H values. Therefore, severely charred feathers should be avoided when selecting feathers for δ 2 H‐based assessment of geographic origin.

Rapid Communications in Mass Spectrometry↗
USGS2018

Genetic analyses reveal cryptic introgression in secretive marsh bird populations

Hybridization is common in bird populations but can be challenging for management, especially if one of the two parent species is of greater conservation concern than the other. King rails (Rallus elegans) and clapper rails (R. crepitans) are two marsh bird species with similar morphologies, behaviors, and overlapping distributions. The two species are found along a salinity gradient with the king rail in freshwater marshes and the clapper in estuarine marshes. However, this separation is not absolute; they are occasionally sympatric, and there are reports of interbreeding. In Virginia, USA, both king and clapper rails are identified by the state as Species of Greater Conservation Need, although clappers are thought to be more abundant and king rails have a higher priority ranking. We used a mitochondrial DNA marker and 13 diagnostic nuclear single nucleotide polymorphisms (SNPs) to identify species, classify the degree of introgression, and explore the evolutionary history of introgression in two putative clapper rail focal populations along a salinity gradient in coastal Virginia. Genetic analyses revealed cryptic introgression with site-specific rates of admixture. We identified a pattern of introgression where clapper rail alleles predominate in brackish marshes. These results suggest clapper rails may be displacing king rails in Virginia coastal waterways, most likely as a result of ecological selection. As introgression can result in various outcomes from outbreeding depression to local adaptation, continued monitoring of these populations would allow further exploration of hybrid fitness and inform conservation management.

Georgia, New Jersey, North Carolina, Rhode Island,↗
USGS2018

State‐space modelling of the flight behaviour of a soaring bird provides new insights to migratory strategies

Characterising the spatiotemporal variation of animal behaviour can elucidate the way individuals interact with their environment and allocate energy. Increasing sophistication of tracking technologies paired with novel analytical approaches allows the characterisation of movement dynamics even when an individual is not directly observable. In this study, high‐resolution movement data collected via global positioning system (GPS) tracking in three dimensions were paired with topographical information and used in a Bayesian state‐space model to describe the flight modes of migrating golden eagles ( Aquila chrysaetos ) in eastern North America. Our model identified five functional behavioural states, two of which were previously undescribed variations on thermal soaring. The other states comprised gliding, perching and orographic soaring. States were discriminated by movement features in the horizontal (step length and turning angle) and vertical (change in altitude) planes and by the association with ridgelines promoting wind deflection. Tracked eagles spent 2%, 31%, 38%, 9% and 20% of their daytime in directed thermal soaring, gliding, convoluted thermal soaring, perching and orographic soaring, respectively. The analysis of the relative occurrence of these flight modes highlighted yearly, seasonal, age, individual and sex differences in flight strategy and performance. Particularly, less energy‐efficient orographic soaring was more frequent in autumn, when thermals were less available. Adult birds were also better at optimising energy efficiency than subadults. Our approach represents the first example of a state‐space model for bird flight mode using altitude data in conjunction with horizontal locations and is applicable to other flying organisms where similar data are available. The ability to describe animal movements in a three‐dimensional habitat is critical to advance our understanding of the functional processes driving animals’ decisions.

Functional Ecology↗
USGS2018

Conservation threats and priorities for raptors across Asia

With long coastlines and some of the world’s most important rivers, mountain ranges, high-altitude plateaus, and islands, Asia is the largest and most populous continent in the world (Lyde 1904; Spencer 1954; Population Reference Bureau 2016). Asia supports all major terrestrial ecosystems and all major climatic types (Galloway et al. 1998; Braimoh and Huang 2015). These include barren ice fields and taigas in North Asia; boreal forests and cold deserts in West, Central, and East Asia; temperate and tropical forests (wet and dry) in East and Southeast Asia; and grasslands in Central and South Asia (Udvardy 1975; Braimoh and Huang 2015). Together, the ecoregions of Asia foster some of the greatest biodiversity on Earth, including six (24%) of 25 global biodiversity hotspots (Myers et al. 2000).

Book chapter↗
USGS2018

Golden eagle (Aquila chrysaetos) habitat selection as a function of land use and terrain, San Diego County, California

Beginning in 2014, the U.S. Geological Survey, in collaboration with Bloom Biological, Inc., began telemetry research on golden eagles ( Aquila chrysaetos ) captured in the San Diego, Orange, and western Riverside Counties of southern California. This work was supported by the San Diego Association of Governments, California Department of Fish and Wildlife, the U.S. Fish and Wildlife Service, the Bureau of Land Management, and the U.S. Geological Survey. Since 2014, we have tracked more than 40 eagles, although this report focuses only on San Diego County eagles. An important objective of this research is to develop habitat selection models for golden eagles. Here we provide predictions of population-level habitat selection for golden eagles in San Diego County based on environmental covariates related to land use and terrain.

California↗