Monument eagles fitted with transmitters
Four nests chosen for study
This summer juvenile Golden Eagles in Canyons of the Ancients National Monument will be fitted with transmitter backpacks for satellite monitoring.
The U.S. Fish and Wildlife Service and the Bureau of Land Management have identified four nests within the monument for the study.
Professional climbers will either climb up to or rappel down the cliff to the nest. Last year four juveniles were tagged. This year biologists hope to tag two more.
“Kinder Morgan deserves credit for conducting surveys identifying raptor nest sites in the monument” said Nathan West, a wildlife biologist with the BLM Tres Rios office.
An archaeologist will clear the area before the climb, and if cultural resources are present, climbers will adjust routes.
Once in the nest, biologists will capture a juvenile eagle and it will be raised or lowered to be fitted with the a “PTT” satellite transmitter on its back and returned to the nest.
“Last year the BLM observed the tagging and it went smoothly,” West said. “Trained experts do the tagging and are very professional. The birds don’t just lay down for it, but they’re calmer after a hood is placed over their head.”
A similar program last year tagged golden eagles in the monument and tracked them to Wyoming and Sleeping Ute Mountain. An eagle tagged near Flagstaff, Ariz., left nest and flew 250 miles to a new home range in the San Juan Mountains.
The tagging project is part of a larger study in the Southwest that monitors juvenile eagle movements and mortality. Golden eagle populations have been declining rangewide, and the cause is not known. The project will provide insight into population dynamics of the iconic bird.
There are an estimated 30,000 golden eagles in the U.S., but juveniles in the southern Rockies have suffered a mysterious decline.
“They are prone to electrocution, and the electric co-ops have been good at designing infrastructure so that does not happen,” West said. “They retrofit old lines as well to accommodate raptors.”
In 2010, Fish and Wildlife in the Southwest region partnered with the Jicarilla Apache Nation, Navajo Nation, Southern Ute Tribe, and the BLM to document golden eagle behavior and causes of mortality in the Four Corners.
According to a Fish and Wildlife report in the Sonoran Joint Venture, yearly mortality of golden eagles, excluding adults, averages 40 percent, a relatively high level. Mortality in the months after fledging is high because of starvation caused by drought, which lowers populations of prey animals such as rabbits.
Recent losses included one juvenile eagle that drowned in a steep-sided pool in a sandstone niche. Another was killed by a mountain lion at a deer carcass. Lead poisoning from consuming carcasses with lead bullets also occurs.
The transmitter units weigh 1.5 ounces, provide hourly locations accurate to within 50 to 75 feet, and last three years.
Biologists monitor eagle movement via satellite so they can respond quickly if lack of movement suggests death or injury.
“We will reach a project goal of tagging at least 50 young eagles with PTTs in the coming months,” wrote biologist Robert Murphy.
A pattern emerging is that nonbreeding Golden Eagles from the Four Corners region reside in more northerly places during late spring through late fall. Some prefer remaining at elevations of 10,000 to 13,000 feet during the summer, including in the San Juan Mountains.
One juvenile bird that was captured and tagged on the Navajo Nation traveled to Chihuahua, Mexico, the southernmost movement of a juvenile originating in the Four Corners area.