Forty-six volunteers spent the morning of Jan. 10, 2009, searching for bald and golden eagles across the Powder River Basin in Wyoming. Their efforts were part of the nationwide midwinter bald eagle survey, coordinated locally by the Bureau of Land Management (BLM) Buffalo Field Office and the U.S. Fish and Wildlife Service.
Volunteers counted 197 bald eagles and 72 golden eagles on established survey routes along 1,300 miles of public roads. Sightings of several other raptor species were also reported, including rough-legged hawks, red-tailed hawks, and American kestrels.
Eagle observations were mostly concentrated in the foothills along Interstate 90 between Sheridan and Buffalo and in the cottonwood riparian areas along Clear Creek. In these areas, road kill, fish, and waterfowl provide valuable winter forage, while trees offer roosting sites where the eagles can keep warm at night.
The midwinter bald eagle survey has been conducted in the Powder River Basin since 2006. In 2006, there were119 eagles counted. The 2007 and 2008 surveys found 300 and 157 eagles. These survey totals vary due to the number of routes covered in each year but are also influenced by weather and the availability of food sources including carrion, prairie dogs, and rabbits. The high number of eagles observed in the 2007 survey likely coincides with the high in the cottontail rabbits’ natural population cycle that year.
While hundreds of bald and golden eagles are seen in the basin during the winter months, only a few stay year-round. Approximately 10 to12 bald eagle pairs nest in the area. A greater number of golden eagles remain in the Powder River Basin, with nesting activity confirmed at 89 nests in 2008. The winter populations migrate north in March and April, returning to northern Canada and Alaska.
This year’s level of public participation by individuals from Campbell, Johnson, and Sheridan counties meant that all 48 established survey routes were covered, and an additional experimental route was created. “Volunteers are essential to the success of the midwinter survey,” said BLM wildlife intern Charlotte Darling, “We were very pleased to have the involvement of both past volunteers and new participants in this year’s count. Their dedication and interest in local raptors will help wildlife managers continue to monitor the Basin’s winter eagle population.”
The national midwinter bald eagle survey began in 1979 as an effort to identify wintering habitat and develop a total population index for the struggling eagle population in the lower 48 states. Collecting eagle data over the long-term has allowed analyses of population trends that help to monitor the health of the species as a whole.
If you are interested in volunteering next year, or would like additional information, contact Charlotte Darling at (307) 684-1045 or Brad Rogers at (307) 684-1046. For more information on the national program and its results visit the U.S. Geological Survey Snake River Field Station website at http://srfs.wr.usgs.gov/research/indivproj.asp?SRFSProj_ID=2.