The Eagle has Landed: Winter Eagle Research Takes Flight in the Bitterrroot Valley

We began capturing Golden Eagles on the MPG Ranch in the Bitterroot Valley in 2011. Though we began with the intent of using satellite transmitters to learn about the habitat use and migration paths of adult, overwintering Golden Eagles, our research has evolved to encompass placing auxiliary markers on Golden and Bald Eagles of all ages. We also test eagles for environmental contaminants. So far we have captured and marked more than 75 Golden and 20 Bald Eagles. Due to these markers, we've amassed an impressive archive of eagle re-sightings in the Bitterroot Valley and other locations, including Washington and British Columbia. We've also learned that the majority of eagles captured show signs of lead exposure, likely from the ingestion of lead ammunition fragments. This year, we expanded efforts to study wintering eagles throughout the Bitterroot Valley. We've joined forces with Bitterroot Audubon and private landowners to set out carcass and camera stations on private lands throughout the valley. These efforts should increase the likelihood of re-encountering our marked eagles, demonstrate the value of private lands to eagles and other scavengers, and engage people from a variety of backgrounds with our research. We will share preliminary results from this collaboration, including impressive camera “captures” of Bald Eagles, Golden Eagles, and other scavengers. We will also share information about the public platform we are using to crowd-source image identification; this platform is available for other camera-trapping projects in Montana

Wing-Tagged Encounters of Goldens Eagles Captured in Montana (Poster)

Recently, there has been an increase in concern for Golden Eagle (Aquila chrysaetos) populations in the western United States. The concern stems from a marked decrease in the number of migrants and concern over an increase in future threats from a variety of anthropogenic factors including, but not limited to, energy development. Thus, there is a need for more information on Golden Eagles including: where they winter, longevity, causes of mortality and critical habit needs. Standard banding offers low encounter rates (<7%) and satellite telemetry is cost prohibitive. We began auxiliary marking Golden Eagles with vinyl wing-tag markers as a cost effective means to gather information on the species. Since 2004, we have wing-tagged over 214 eagles, and re-encountered 46 individuals, giving us a 21% encounter rate. This technique is proving considerably more effective than banding alone as a means of identifying individuals and receiving re-encounter information. We attribute this success, in part to internet information sharing and the increasing use of remote cameras set up on carcasses to view scavenger activity

Blood-Lead Levels of Wintering Golden and Bald Eagles of the Bitterroot Valley Montana (Poster)

Lead has long been documented as a serious environmental hazard to eagles and other predatory, opportunistic and scavenging avian species. The use of lead shotgun pellets for waterfowl hunting on federal and state lands was banned in 1991 due to lead poisoning in Bald Eagles (Haliaeetus leucocephalus), Golden Eagles (Aquila chrysaetos) and numerous waterfowl species. At that time, this was thought to be the major source of the lead exposure. More recently, lead poisoning from ingested lead-bullet fragments and shotgun pellets has been identified as the leading cause of death in California Condors (Gymnogyps californianus), leading to a ban of lead ammunition within the “California Condor Recovery Zone.” Another on-going study on Common Ravens (Corvus corax) and Bald Eagles in Wyoming has shown a direct correlation between very high blood-lead levels and the on-set of rifle hunting season. Indeed, there is overwhelming evidence showing that lead toxicity is still prevalent in the environment and mounting data points to fragmented rifle bullets as the source. We sampled blood from 32 Golden Eagles and 11 Bald Eagles captured on wintering grounds in the Bitterroot Valley from 2011 - Present. Eighty-six percent of eagles tested showed blood-lead concentrations higher than natural background levels. These preliminary results suggest exposure to lead is prevalent among eagles from northern latitudes wintering in the Bitterroot Valley

Wing-Tagged Encounters of Golden Eagles Captured in Montana

Recently, there has been an increase in concern for Golden Eagle (Aquila chrysaetos) populations in the western U.S. The concern stems from a marked decrease in the number of migrants and future threats from a variety of anthropogenic factors including industrial energy development. Thus, there is a need for more information on Golden Eagles including: where they winter, longevity, causes of mortality and critical habitat needs. Standard banding offers low encounter rates (ca. 7%) and satellite telemetry is cost prohibitive for large sample sizes. We began auxiliary marking Golden Eagles with vinyl wing-tag markers as a cost effective means to gather information on the species. Since 2004, we have wing-tagged 260 eagles, and re-encountered 59 individuals, giving us a 23% encounter rate. This technique is proving considerably more effective than banding alone as a means of identifying individuals and receiving re-encounter information. We attribute this success, in part, to internet information sharing and the increasing use of remote cameras set up on carcasses to view scavenger activity. Given our observed encounter rates, we suggest utilizing wing-tags as a form of auxiliary marking to augment studies where standard banding is the lone marking method

Epaulets in Golden Eagle Plumages in Western Montana

An uncommon plumage characteristic of North American Golden Eagles (Aquila chrysaetos) is the epaulet, a white feather or feathers at the shoulder, often symmetrical on both sides in appearance. The size and shape of an epaulet varies by individual. This characteristic is mentioned within the literature, but is not noted how it is reflected within a population. We have observed epaulets in 17 out of 102 (16.6%) individual Golden Eagles with at least one epaulet in western Montana since 2012. Of these individuals, 13 (76.4%) were observed on the Rocky Mountain Front while on migration, and 4 (23.6%) were observed on wintering grounds in the Bitterroot Valley, Montana. Epaulets have been observed on both male and female individuals, and on both sub-adult and adult aged birds. This plumage characteristic should continue to be recorded in Golden Eagles for a better estimate of rate of occurrence within a population

Estimating Natal Origins of Migratory Juvenile Northern Goshawks Using Stable Hydrogen Isotopes

From 2004 to 2007, we collected hatch-year feathers from 44 juvenile Northern Goshawks (Accipiter gentilis) captured at our Rocky Mountain Front banding station near Lincoln, Montana. Due to the relative scarcity and secretive nature of goshawks, little is understood about their migration patterns or the geographic origins of birds encountered at research sites. Most studies suggest goshawks are partial migrants, often moving <100km, but select band returns and radio and satellite telemetry have shown some individuals occasionally travel thousands of kilometers. We performed a stable hydrogen isotope analysis on the feathers we collected from young goshawks to determine their predicted natal origin. We found that 68% of goshawks had predicted natal origins relatively close to our capture site, 25% from areas in northwestern Canada and eastern Alaska, and 7% somewhere significantly south or east of our capture site. We did not find any significant patterns with sex and passage date or latitudinal origin, nor did we find a meaningful relationship between latitudinal origin and passage date. Our findings support the current understandings of goshawk migration, with a majority of individuals traveling short distances from their natal grounds and a few outliers traveling great distances, not always in a southerly direction

Satellite Telemetry Provides Insight into Where Western Montana Osprey Spend the Winter

During a long-term study of Osprey (Pandion haliaetus) in western Montana on demography and ecotoxicology, migratory information on several birds was collected. It is important to know where these birds migrate and spend the winter because 2/3 of their lives are spent outside Montana. Since virtually nothing was known about where these birds go when they leave the state, in 2012 and 2013 we put satellite transmitters on two families of Osprey (adults and chicks) from nests near Florence, Montana. Telemetry data show that these birds migrate south through a fairly narrow corridor to Arizona and New Mexico, but then go in different directions:  some individuals spend the winter in Texas, and others migrate to Mexico and as far south as the Nicaragua-Costa Rica border on both the Atlantic and Pacific coasts. Migration pathways of the adults were very similar for both south-bound and north-bound migrations across multiple years

Migrating and Overwintering Populations of Diurnal Raptors in the Bitterroot Valley, Montana

We identified a major spring and fall migration of diurnal raptors over a low-elevation foothills site in the northeast Bitterroot Valley. We conducted full-time migration surveys in both seasons for 2 years. Red-tailed Hawks were the most abundant species counted in both seasons. During fall migration, species composition differed from other Montana hawk watch sites located on high-elevation ridges. We used a combination of survey techniques to assess overwintering populations of raptors in the Bitterroot Valley during the winter of 2012-2013. We developed an iPad application that allows us to map fine-scale occurrence of birds and used this method to document raptor presence at the north end of the valley. Citizen Scientists affiliated with Bitterroot Audubon performed systematic, broader-scale surveys at the south end of the valley. These two methods will likely document over 3,000 raptor observations by the end of winter 2013. Rough-legged and Red-tailed Hawks comprise the majority of raptor detections. We will examine these data for spatial and temporal trends in raptor occurrence

Montana Peregrine Falcon Survey: 2012

The release of 617 captive-bred young during the 1980’s and 1990’s sparked the recovery of the Peregrine Falcon (Falco peregrinus) in Montana. By 1994, a mix of state, federal, and private biologists (Montana Peregrine Falcon Working Group) documented 13 known active Peregrine Falcon territories. For the following four years, the number of known territories averaged about 16, but then intensive survey efforts in 1999 documented a total of 28 territories. The number of active Peregrine Falcon territories discovered in Montana has increased yearly. Montana had a record number of 108 active Peregrine Falcon nests recorded during the 2012 field season. Montana Peregrine Falcon surveys are conducted in conjunction with the USDI Fish and Wildlife Service national surveys scheduled every 3 years, beginning in 2002 and ending in 2015. Annual survey objectives include the establishment of a citizens group (Project Peregrine Watch) to monitor individual Peregrine territories throughout the state, determine status and trends of Montana’s Peregrine Falcon population, study all known historic Peregrine Falcon eyries, record occupancy and productivity at all active territories, locate new Peregrine Falcon territories, seek confirm and consolidate information from all public and private sources, record activity and locations of neighboring cliff-nesting raptors (Prairie Falcon (Falco mexicanus), Golden Eagle (Aquila chrysaetos), and the Red-tailed Hawk (Buteo jamaicensis), and develop , a long-term and cost-effective monitoring program for determining annual status and population trends of the State’s Peregrine Falcon population

Golden Eagle Migration Corridors along The Rocky Mountain Front and Intermountain Flyways

Golden Eagles (Aquila chrysaetos) have been receiving increased attention in the western United States due to an increase in anthropogenic population threats, including wind and other industrial energy developments. Conservation of migratory Golden Eagles hinges on knowledge of threats within breeding ranges, migratory corridors, and over-wintering areas. Often, understanding threats along migration corridors can be difficult due to the short temporal use of migration paths and because pathways can often be dispersed across the landscape. We used satellite tracking data from three Golden Eagle studies across Montana to estimate key migration routes and bottlenecks for migratory Golden Eagles wintering or passing through Montana, with an emphasis on the Rocky Mountain Front. We gathered data from 35 individuals, including from 21 adult and 14 sub-adult Golden Eagles. We created individual dynamic Brownian Bridge Movement Models (dBBMM) for each migration event to estimate migratory pathways of individuals. We also created a population level migratory pathway estimate to determine key migration corridors and bottlenecks by summing the individual dBBMMs after accounting for age and study location. These models can be used for future risk assessments for developments and conservation measures for Golden Eagle migration routes