Habitat Use of Over-Wintering Adult Godlen Eagles in the Western U.S.

A number of studies show declining migration count trends and breeding abundance in Golden Eagles (Aquila chrysaetos) in the West. We outfitted 13 adult, migrant Golden Eagles with transmitters from 2007-2012 with battery powered Argos Platform Terminal Transmitters (PTT) or 70-g solar-powered GPS/PTTs. Eagles wintered across the West, from central Montana to Arkansas. We gathered data on winter territory size, time spent on wintering grounds, and the habitat use of eagles during the winter. We measured a large degree of variability in both winter home range size and duration of winter range use. We found an average 50-percent Minimum Convex Polygon (MCP) home range estimate of 1680 km2 (range 8-14,881 km2) and an average 95-percent MCP of 6578 km2 (range 85- 36,143 km2). Winter home range estimates were extremely variable between individuals and even within the same individual between years. Eagles spent an average of 105 days on their wintering territories (range 60-179 days). We found the most common habitat types were pinyon-juniper, coniferous forest, grassland, shrub, and sagebrush habitats which all comprised ?10 percent of core wintering areas. Several habitat types were correlated to latitude and longitude: the percentage of coastal habitat within winter home ranges increased as eagles wintered further south, riparian and logged habitats increased to the north and west, and shrub habitat percentage of the home range decreased with an increase in latitude. Understanding wintering needs of Golden Eagles is essential to the long-term health of this species across the West

Identifying Factors Influencing Presence and Reproductive Success of a Golden Eagle Population in South Central Montana

Golden Eagles (Aquila chrysaetos) in the western U.S. have received increased attention due to an apparent decline in the number of annual migrants and expected increased risk from energy development. Long-term research focused on resident, breeding Golden Eagles in this region is rare and sorely needed to assess the degree of population decline. In addition, managers require the identification of factors that influence presence and breeding success of Golden Eagles to create an effective management strategy. Beginning in 2010, we revisited a historically surveyed study site near Livingston, Montana. Our objective was to compare the current status of the Golden Eagle breeding population to that from the 1960’s and to identify factors necessary for maintaining Golden Eagle populations. In the last 3 breeding seasons, we have documented a near 100-percent occupancy rate of historic territories and a marked increase in the number of breeding pairs. Our results also indicate that factors related to prey availability most strongly influenced nest site selection and reproductive success. Based on our current results, we suggest Golden Eagle populations may remain strong in some locations and management strategies should focus on maintaining prey habitat

Estimating Survival and Determining Causes of Mortality of Golden Eagles in South-Central Montana

There is concern for golden eagles (Aquilla chrysaetos) in the West as a result of contradictory population trend estimates and a likely increase in threats including but not limited to expanded wind energy development.  Estimating survival of golden eagles and identifying causes of mortality can be used to assess the viability of nesting golden eagle populations and to direct mitigation efforts if necessary.  To date, little information exists on golden eagle survival in western North America.  In addition, identified causes of golden eagle mortality are often associated with an opportunity to find dead birds, creating a potential bias that may be minimized with the use of satellite telemetry.  We outfitted 17 adult and 13 nestling golden eagles with satellite transmitters during the 2011-2014 nesting seasons near Livingston, Montana to estimate survival and determine causes of mortality.  We used multi-state models to estimate survival over discrete-time periods for both adults and nestlings.  Preliminary results showed our survival estimates were consistent with similar long-lived, slow reproducing raptors.  Golden eagle mortalities in our study were a result of poisoning, intraspecific interaction and poaching.  Our survival estimates are consistent with the stable density of breeding golden eagles in our study area and the primary causes of mortality differed from repository-based studies

Avian Scavengers And Lead Rifle Ammunition: Where We’re At, Challenges, And Solutions

Birds have long been recognized at risk of lead poisoning from ammunition sources, but only in recent years has rifle ammunition been identified as a source of lead toxicity in raptors and other scavenging birds. Several studies have indicated increased lead exposure in eagles but the implications to population dynamics remain unclear. We have monitored blood lead levels of Common Ravens (Corvus corax), Bald Eagles (Haliaeetus luecocehpalus), and Golden Eagles (Aquila chrysaetos) in Jackson Hole, Wyoming, since 2004 to investigate effects of spent rifle ammunition on avian scavengers. Data from ravens and Bald Eagles indicated a strong relationship between big-game hunting seasons and elevated blood lead levels. In 2009, we initiated a voluntary non-lead ammunition program in collaboration with Grand Teton National Park and the National Elk Refuge. Free, non-lead ammunition was distributed to hunters in the area. Hunter surveys indicated that 24 percent of successful hunters on the Park and Refuge used non-lead ammunition and we detected a 28-percent drop in the mean lead levels of ravens monitored from previous years after the harvest totals were controlled for. We continued the voluntary program in 2010 by selling reduced-priced non-lead ammunition, and there was greater participation in the voluntary non-lead program (33%). Further, we have outfitted 13 Bald Eagles with satellite transmitters to document the potential geographic impact our local hunting season has on the continental eagle population and found that 90 percent of eagles outfitted during the big-game hunting season breed/ summer in central Canada

50-Year Golden Eagle Nesting Trends In South-Central Montana

Golden Eagle (Aquila chrysaetos) migration counts in the western North America have shown a significant negative trend in recent years. However, the causes of these declines are unknown and it remains unclear if declining migration counts correlate to a declining population or changes in migratory behavior. Long-term research on nesting Golden Eagle populations is lacking and is needed to properly assess the current Golden Eagle population status in many areas. In 1962, intensive monitoring efforts were initiated in a roughly 1200-mi2 study area in south-central Montana. The objectives were, among other things, to determine density and productivity of Golden Eagles. This area was re-surveyed in the mid 1990s to begin looking at long-term population trends. In 2009, we initiated a multi-year effort to investigate potential changes in the nesting trends in the same study area over a half a century. The data collected to date indicate an increase in the nesting density, similar nest success rates, and a decrease in productivity when compared with both the 1960’s and 1990s studies. The longevity of data collected in this study area allows for one of the longestterm comparisons for Golden Eagle nesting density and success in the West and provides invaluable insights into the status of nesting Golden Eagles in this region

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

Montana Golden Eagle Conservation Guidelines

The Montana Golden Eagle Working Group is preparing guidelines to address conservation concerns for golden eagles (Aquila chrysaetos) related to land use change and population-level mortality factors. The guidelines focus primarily on avoiding, minimizing and mitigating adverse impacts to golden eagles.  The USDI Fish and Wildlife Service Draft Conservation Plan Guidance explains the Service’s approach to issuing programmatic permits for eagle take and provides adaptive management guidance for the conservation of golden eagles related to land-based wind energy facilities. The Montana guidelines are intended to address a wider array of golden eagle conservation concerns and potential anthropogenic impacts, and compliment implementation of the industry-focused Draft Eagle Conservation Plan Guidance in Montana.  We will present a summary of the status of and threats to golden eagle populations and habitats. Then we will discuss our draft conservation guidelines that outline strategies for maximizing reproductive potential and survival of the eagle population in Montana. We also will present some options for mitigation when negative impacts to eagles cannot be avoided or minimized

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

This article contains an analysis of 16 microstatellite loci from 300 Greater Sage-Grouse individuals to assess genetic structure among populations in Wyoming and southeast Montana