Bryan Bedrosian

Blood Lead Levels of Common Ravens With Access to Big-Game Offal

Abstract Despite increased knowledge about environmental toxins and changes in lead use (i.e., the mandated use of nonlead paint, gasoline, and shotgun pellets used for hunting waterfowl on federal lands), lead poisoning continues to occur in terrestrial birds. The degree of exposure and its demographic effect, however, continue to be described, emphasizing the growing concern over lead exposure. We examined 302 blood samples from common ravens (Corvus corax) scavenging on hunter-killed large ungulates and their offal piles to determine if lead rifle-bullet residuum was a point source for lead ingestion in ravens. We took blood samples during a 15-month period spanning 2 hunting seasons. Of the ravens tested during the hunting season, 47% exhibited elevated blood lead levels (≥10 μg/dL) whereas 2% tested during the nonhunting season exhibited elevated levels. Females had significantly higher blood lead levels than did males. Our results confirm that ravens are ingesting lead during the hunting season and ...Abstract Despite increased knowledge about environmental toxins and changes in lead use (i.e., the mandated use of nonlead paint, gasoline, and shotgun pellets used for hunting waterfowl on federal lands), lead poisoning continues to occur in terrestrial birds. The degree of exposure and its demographic effect, however, continue to be described, emphasizing the growing concern over lead exposure. We examined 302 blood samples from common ravens (Corvus corax) scavenging on hunter-killed large ungulates and their offal piles to determine if lead rifle-bullet residuum was a point source for lead ingestion in ravens. We took blood samples during a 15-month period spanning 2 hunting seasons. Of the ravens tested during the hunting season, 47% exhibited elevated blood lead levels (≥10 μg/dL) whereas 2% tested during the nonhunting season exhibited elevated levels. Females had significantly higher blood lead levels than did males. Our results confirm that ravens are ingesting lead during the hunting season and are likely exposed to lead from rifle-shot big-game offal piles.

Lead exposure in bald eagles from big game hunting, the continental implications and successful mitigation efforts.

Studies suggest hunter discarded viscera of big game animals (i.e., offal) is a source of lead available to scavengers. We investigated the incidence of lead exposure in bald eagles in Wyoming during the big game hunting season, the influx of eagles into our study area during the hunt, the geographic origins of eagles exposed to lead, and the efficacy of using non-lead rifle ammunition to reduce lead in eagles. We tested 81 blood samples from bald eagles before, during and after the big game hunting seasons in 2005–2010, excluding 2008, and found eagles had significantly higher lead levels during the hunt. We found 24% of eagles tested had levels indicating at least clinical exposure (>60 ug/dL) during the hunt while no birds did during the non-hunting seasons. We performed driving surveys from 2009–2010 to measure eagle abundance and found evidence to suggest that eagles are attracted to the study area during the hunt. We fitted 10 eagles with satellite transmitters captured during the hunt and all migrated south after the cessation of the hunt. One returned to our study area while the remaining nine traveled north to summer/breed in Canada. The following fall, 80% returned to our study area for the hunting season, indicating that offal provides a seasonal attractant for eagles. We fitted three local breeding eagles with satellite transmitters and none left their breeding territories to feed on offal during the hunt, indicating that lead ingestion may be affecting migrants to a greater degree. During the 2009 and 2010 hunting seasons we provided non-lead rifle ammunition to local hunters and recorded that 24% and 31% of successful hunters used non-lead ammunition, respectively. We found the use of non-lead ammunition significantly reduced lead exposure in eagles, suggesting this is a viable solution to reduce lead exposure in eagles.

EVALUATION OF TECHNIQUES FOR ATTACHING TRANSMITTERS TO COMMON RAVEN NESTLINGS

Abstract We assessed 4 methods of attaching transmitters to nestling Common Ravens (Corvus corax) in Grand Teton National Park, Wyoming, in preparation for a larger telemetry study. The attachment types included backpack style with a cross-chest harness, rump mount (“figure-8”), necklace, and tarsal mounts. We tested 2 to 5 transmitters of each attachment type and recorded the ease of attachment, agitation of the ravens (from the nestling stage through the post-fledging dependence period) caused by the transmitters, and any noticeable abrasions caused by the attachment. We preferred the tarsal mount attachment because the transmitters can be placed on the bird early in the nestling stage and 1 person can attach it quickly. We did not prefer the other methods. The necklace mount became “bridled” between the birds upper and lower mandible and/or fell off. Backpack and rump mounts required extensive fitting time, and we felt they should not be used until the nestlings had attained maximum growth, reducing the window of time for attachment.

Low neutral genetic diversity in isolated Greater Sage-Grouse (Centrocercus urophasianus) populations in northwest Wyoming

ABSTRACT Identifying small, isolated populations is a conservation priority, not only because isolation may result in negative fitness consequences, but these populations may also harbor unique genetic diversity. The Greater Sage-Grouse (Centrocercus urophasianus) is a widespread obligate species of the sagebrush biome in western North America that has experienced range-wide contraction over the past century. To prevent local extirpation, efforts have been made to identify isolated populations. Here, we analyzed 16 microsatellite loci from 300 Greater Sage-Grouse individuals to assess genetic structure among populations in Wyoming and southeast Montana, particularly with the Jackson Hole and Gros Ventre populations in northwest Wyoming. Four genetic clusters were observed with Pinedale (central-west) and Casper (central) populations forming a cluster, Powder River Basin (central-north) and southeast Montana forming a second cluster, and both Jackson Hole and Gros Ventre forming distinct population clusters. All but the Jackson Hole and Gros Ventre genetic differentiation correspond with designated ecoregions and possessed an isolation-by-distance pattern of differentiation. Both Jackson Hole and Gros Ventre were identified as separate populations with asymmetrical dispersal into Gros Ventre. Both populations also possessed significantly reduced genetic diversity and low effective number of breeders (Nb). Because both populations are surrounded by extensive forested mountain ranges nearly devoid of sagebrush habitat, the Jackson Hole and Gros Ventre populations may have long been isolated from other Greater Sage-Grouse populations; however, only a few alleles were unique to the Jackson Hole and Gros Ventre populations. The observed genetic differentiation was largely due to allele frequency differences rather than private alleles, suggesting some historical gene flow. More work is needed to determine the timing of isolation and whether managers should focus on maintaining and increasing adequate sagebrush habitat, allowing the population to increase in size, or population supplementation to increase genetic diversity.

Habitat Selection and Factors Influencing Nest Survival of Golden Eagles in South-Central Montana

Abstract Golden Eagle (Aquila chrysaetos) population trends in the western United States are unclear, but an increase in future threats is causing concern for the species. Understanding the resource requirements of Golden Eagles will be essential to the creation of an effective management approach. Yet, we currently lack sufficient information on the basic habitat requirements of Golden Eagles, which hinders creation of a successful conservation plan. We took a multiscaled approach to identify factors influencing habitat selection of breeding Golden Eagles in south-central Montana. In addition, we tested environmental factors we predicted would influence daily nest survival rates to understand environmental influences on breeding success. From the 2010–2013 nesting seasons, we located 45 nesting territories and identified 115 apparent nest initiations (defined as nests where eggs have apparently been laid). We collected 15,182 telemetry locations from 12 breeding Golden Eagles. We found that Golden Eagles selected home ranges based on the percent of intermixed shrub and grassland and terrain ruggedness. At the within-home range scale, Golden Eagles selected areas based on aspect, distance to their nest, and an interaction between proximity to prey habitat and terrain ruggedness. Despite Golden Eagle selection of rugged topography, daily nest survival was negatively influenced by topographic ruggedness. Based on our results, we suggest that to maintain breeding pairs of Golden Eagles in areas similar to our study area, management should focus on preserving adequate prey habitat in areas with rugged topography. However, territories with higher ruggedness may not be as productive; therefore, management goals should be clear and environmental factors influencing both habitat selection and reproductive success should be considered when possible.

Using Morphometrics To Determine the Sex of Common Ravens

Abstract We tried using morphometrics to determine sex for a population of Common Ravens (Corvus corax) in northwestern Wyoming. We attempted to correlate 13 external measurements to sex using discriminant function analyses. Sex was verified with a DNA test that identified females with 2 PCR-amplified gene copies (1 each from the W and Z chromosomes) and males with 1 gene copy (only Z chromosome). We created a predictive model of sex of ravens for easy field use. We found that by using 2 separate discriminant functions with footpad length and body mass measurements simultaneously, we were able to correctly classify 97% of female samples, 91% of male samples, and had an unknown category that included 15% of samples.

Space Use and Habitat Selection by Adult Migrant Golden Eagles Wintering in the Western United States

Abstract Recently, there has been an increase in concern for Golden Eagle populations in the western United States, stemming from a marked decrease in the number of migrants and an increase in future threats from a variety of factors including, but not limited to, energy development. Part of an effective conservation strategy for Golden Eagles involves understanding basic requirements of the eagles during both the breeding and nonbreeding seasons. We used PTT and GPS/PTT transmitter data from 14 adult, migratory Golden Eagles captured near the Rocky Mountain Front in Montana to determine the location and size of winter ranges and habitat use and selection within chosen winter ranges. We found large variability in location and size of winter ranges in the western United States. Eagles showed high fidelity to core wintering areas but plasticity in annual range sizes. Adult, migrant Golden Eagles used habitat types associated with perches and primary prey species. Golden Eagles chose areas within winter ranges that were close to prey habitat, within conifer forests and riparian areas, in relatively low elevations, and in areas conducive to orographic uplift. Golden Eagles appeared to avoid urban areas, grassland, agriculture, and non-sagebrush-steppe habitat types. Our results suggest that an effective conservation strategy for migrant Golden Eagles wintering in the western United States should include a large geographic area with heterogeneous habitat allowing for adequate hunting perches and prey habitat, with little urban development or anthropogenic habitat conversion.

Migratory Pathways, Timing, and Home Ranges of Southern Greater Yellowstone Osprey

Rutas Migratorias, Tiempos y Area de Campeo de Pandion haliaetus En El Sur de Yellowstone Durante el periodo 2010–2012 documentamos los movimientos migratorios y estacionales de 11 individuos de Pandion haliaetus que se reproducen o que nacieron en el Parque Nacional Grand Teton, Wyoming. Seguimos los movimientos de los individuos de P. haliaetus con emisores de telemetria satelital a traves de Argos, documentando un total de 13 migraciones otonales y cinco migraciones primaverales. Las fechas de partida promedio durante el otono fueron el 19 de septiembre y el 23 de septiembre para los adultos y juveniles, respectivamente, y los individuos viajaron un promedio de 225 km/d. Los individuos de P. haliaetus presentaron areas de invernada dispersas, generalmente en los alrededores del Golfo de Mexico. La fecha de partida promedio en la primavera fue el 2 de abril y los individuos adultos viajaron un promedio de 269 km/d. Los adultos presentaron un area de campeo en promedio de 176 y 199 ha, considerando el mi...

Synchronous Tail Molt in Great Gray Owls (Strix nebulosa)

Limited information regarding the tail molt sequence of owls suggests that there is variation among and within species in how tail feathers are molted. Some species undergo a gradual tail molt in which rectrices are lost progressively, which may limit loss of tail function or influence energetic constraints (Farner et al. 1972). However, other species molt all rectrices synchronously, or rapidly over a few days, rendering the bird temporarily tailless. This pattern of molting a tail entirely within a short period of time is occasionally referred to as ‘‘simultaneous,’’ but ‘‘synchronous’’ is the more accurate term: simultaneous implies that all the rectrices are lost at once, whereas synchronous denotes that feather loss is rapid but also follows an ‘‘underlying sequence’’ (P. Pyle pers. comm.). Occasionally, in some species, an irregular molt occurs in which some tail feathers are molted and the rest of the rectrices are molted later in the year or in a subsequent year. Although several studies describe the tail molt pattern of various owl species (including a number of Strix species), information on the tail molt of Great Gray Owls (Strix nebulosa) is lacking. Northern Spotted Owls (Strix occidentalis) typically undergo complete tail molts every other year beginning with the third prebasic molt (Forsman 1981), while Tawny Owls (Strix aluco) molt their tails completely each year (Cramp and Simmons 1985, Pyle 1997). Mayr and Mayr (1954) suggested that tail molt is gradual in large owl species (Strix, Bubo, and Tyto) but synchronous in small owls (Otus, Glaucidium, Athene, and Speotyto). However, Piechocki (1968) reported that Tawny Owls lose their tails synchronously, as do Ural Owls (Strix uralensis; Cramp and Simmons 1985). Forsman (1981) noted the prevalence of synchronous tail molt in Northern Spotted Owls in Oregon, although they also exhibited gradual and irregular molt patterns. Conversely, in northern California, synchronous tail molt was rare in Northern Spotted Owls (C. De Juilio pers. comm.). Forsman (1981) also reported that Barred Owls (Strix varia) occasionally undergo a ‘‘simultaneous’’ tail molt. Finally, R. Nero observed at least one Great Gray Owl undergoing a synchronous tail molt, although he ‘‘doubts that synchronous tail molt is a regular occurrence’’ in Great Gray Owls (Heinrich and Calaprice 1993). These observations among Strix species indicate there is variation in how particular species molt their tails and that synchronous molt may be more widespread among large owls than previously suspected. Little documentation exists on molt patterns of Great Gray Owls in particular, because few year-round studies have been conducted on this species. Although previous researchers noted that Great Gray Owls molt their entire tails annually beginning with the second prebasic molt (e.g., Duncan 1996), there has been no documentation of particular molting patterns. We investigated the tail molt patterns of Great Gray Owls as part of an extensive field study on the species conducted in montane forests in western Wyoming, U.S.A. We recorded tail condition during weekly relocations of telemetry-marked owls in 2014 and 2015 and observed 20 instances of Great Gray Owls undergoing synchronous tail molt. In 2014, nine breeding owls, one nonbreeding 1-yrold owl, and two owls with unknown breeding status molted their tails synchronously. In 2015, five breeding Great Gray Owls and three nonbreeding 1-yr-old owls exhibited synchronous tail molt. Rectrices were lost rapidly either in no particular order or centrifugally (from the innermost to outermost), but molt was completed typically within a few days and at the most within 2 wk. We did not observe (either in the hand or through binoculars within 50 m) gradual or irregular tail molt in any owl. Furthermore, every Great Gray Owl banded within our studies (n1⁄4 29) and all observed unmarked owls had even tail molt (all rectrices from the same generation), indicating that they did not undergo an incomplete molt. Two individuals observed subsequently in 2014 and 2015 molted their tail feathers both years and no captured individual had rectrices that appeared more than 1 yr old during banding operations. For Great Gray Owls in western Wyoming, the mean date on which tail molt began was 17 July in 2014 (range 1⁄4 24 June–14 August) and 4 July in 2015 (range 1⁄4 10 June–25 July). Average molt date was 1 July for females (n1⁄411) and 11 July for males (n 1⁄4 9). Our observations indicate that 1 Email address: katherine@tetonraptorcenter.org

Patterns of Spatial Distribution of Golden Eagles Across North America: How Do They Fit into Existing Landscape-scale Mapping Systems?

Abstract Conserving wide-ranging animals requires knowledge about their year-round movements and resource use. Golden Eagles (Aquila chrysaetos) exhibit a wide range of movement patterns across North America. We combined tracking data from 571 Golden Eagles from multiple independent satellite-telemetry projects from North America to provide a comprehensive look at the magnitude and extent of these movements on a continental scale. We compared patterns of use relative to four alternative administrative and ecological mapping systems, namely Bird Conservation Regions (BCRs), U.S. administrative migratory bird flyways, Migratory Bird Joint Ventures, and Landscape Conservation Cooperatives. Our analyses suggested that eagles initially captured in eastern North America used space differently than those captured in western North America. Other groups of eagles that exhibited distinct patterns in space use included long-distance migrants from northern latitudes, and southwestern and Californian desert residents. There were also several groupings of eagles in the Intermountain West. Using this collaborative approach, we have identified large-scale movement patterns that may not have been possible with individual studies. These results will support landscape-scale conservation measures for Golden Eagles across North America.