Tracking Golden Eagles

March 6, 2015 by Amy Scarpignato

 

Together with Brian Smith of the USFWS Division of Migratory Birds Region 6 and colleagues, the Smithsonian Migratory Bird Center is deploying cell phone transmitters on Golden Eagles to understand the overwintering movements and the breeding locations of birds wintering in the Colorado-Wyoming region.

Mike Lockhart with a hatch-year Golden Eagle. Juvenile Golden Eagles have white at the base of the tail while adults have mostly dark brown tails.

Migratory connectivity is critical information for understanding eagle biology, informing policy and for making management decisions. Currently, Golden Eagles are managed within Bird Conservation Region boundaries. However, this region hosts a mix of wintering eagles from different breeding populations, alongside year-round resident eagles, complicating complete and effective management decisions. Since birds that winter here also may be affected by factors on their breeding grounds, biologists are only getting half the story.

Preliminary data from Golden Eagles across the country suggests that mixing strategies may be more common than previously thought for wintering birds. Answering questions such as where wintering populations breed and what percentage of wintering birds are migratory is essential to effective management of Golden Eagles in this and other regions.

In December 2014, Mike Lockhart (contractor to USFWS) and his volunteers captured two hatch-year (born in 2014) male Golden Eagles near the Colorado-Wyoming border. Solar-powered GPS-GSM transmitters were deployed on both eagles. GSM (Global System for Mobile Communications) transmitters use the cellular network to transmit GPS locations of the eagle to the researcher.

Golden Eagle with solar-powered cell phone transmitter.
The map shows GPS locations of two hatch-year male Golden Eagles (red and orange) from cell phone transmitters deployed in December 2014. Points in red are eagle locations from one week in December. Points in orange are eagle locations from December to early February. The cell phone transmitters collect approximately 35 locations per day. However, soon after deployment the number of transmissions decreased. This is most likely due to the solar-powered transmitter batteries not staying charged through this cold and snowy winter.
Volunteer releasing a Golden Eagle with transmitter near the Colorado-Wyoming border.