Cheatgrass cheating eagles out of habitat
Juab County • The natural instinct to defend themselves took different courses for the two young golden eagle siblings in the nest atop the juniper tree.
The male eaglet stood his ground, displaying an already formidable beak and talons in an effort to stare down the threat.
The female lay under her wings hoping the intruder would mistake her as part of the carrion-littered nest.
Neither tactic worked against HawkWatch International field technician Eric Chabot, who placed hoods on the chicks, gently placed them in a bag and lowered them to the ground where other members of the HawkWatch team were waiting.
Twenty-two such encounters will take place this spring as young golden eagles in Utah are outfitted with telemetry devices allowing researchers to see what happens during that important first year of life, and hopefully, well beyond.
"We get some information when people find dead raptors with bands, but that only happens when people find them and then tell us about it," said HawkWatch International conservation Director Steve Slater. "With telemetry, if an eagle dies in the middle of the salt flats, we can retrieve the bird and see what caused its death."
Researchers can also track, with nearly pinpoint accuracy, where raptors outfitted with the telemetry devices go in the four or so years from the time they learn to fly until they build a nest and lay their own eggs.
The telemetry program is part of "The Utah Legacy Raptor Project" funded by the Department of Defense Legacy Resource Management Program and involves Dugway Proving Ground, Hill Air Force Base, the Bureau of Land Management, U.S. Fish & Wildlife Service and the Utah Division of Wildlife Resources.
The partners came together in 2009 to determine long-term effects of nonnative and invasive cheatgrass on raptor habitat. The results were troubling. Trends showed an up to 50 percent decline in nesting activity in the study area, centered mostly on an area known as the Military Operating Area more commonly referred to as Utah's West Desert.
"We are interested in the regional trends of golden eagles," said Robbie Knight, natural-resources manager of the roughly 900,000-acre U.S. Army Dugway Proving Ground. "If the military operations were having adverse effects on eagles, then it was something we want to be sensitive to. Based on what we are finding, it is regionwide phenomena."
Those results were both comforting and disturbing to Knight.
"The decline of the presence of eagles from the Utah landscape is concerning to everybody," Knight said.
As an invasive species, cheatgrass outcompetes native plants and soon dominates the land. Cheatgrass areas are more prone to wildfire, and they burn more frequently and more intensely.
Most important to golden eagles, the nonnative vegetation is not something jackrabbits, the eagles' main food, and other potential prey use as a source of nourishment or cover.
"In 2007, we had a huge spike in wildfires," Slater said, "and, in 2008, we saw occupancy rates about halved on those areas and since then, including this year, it has remained the same."
HawkWatch officials also found that eagles on the fringe of burn areas, like those on the edge of the salt flats where the fire failed, were doing better than golden eagles that had territories that had gone up in smoke.
"Eagles look around [at cheatgrass environments] and think it looks like good cover for rabbits," Knight said. "They lay an egg, hatch a chick and go out to a sea of cheatgrass and are not able to get sufficient food."
HawkWatch identified 42 active golden eagle nests with eggs this year for possible telemetry placements. When it came time to start placing the devices, there were fewer than 20 nests with chicks. Fortunately, enough of the nests contained two chicks to help the project reach its goal of setting 22 units.
"The eggs hatched, but the chicks had disappeared," Slater said. "It is really interesting how some eagle parents can't make a living for one chick while some parents pull off two chicks that are ginormous."
That was the case for the two eaglets on top of the juniper tree, which were both healthy and close to adult size.
Slater and his crew plucked feathers for DNA testing and placed the 1.5-ounce, 4-inch-long telemetry units (complete with mini solar panels) on the raptors using special harnesses designed by HawkWatch before returning them to the nest. Slater is curious to see if they will stay in Utah, like most golden eagles do year-round, or depart for greener pastures populated with more food.
That was the case with one of six golden eagles at Dugway Proving Ground that Knight was able to attach a unit to several years ago. A female took off and headed north over Twin Falls, Idaho, onto Missoula, Mont., and eventually ended up in northern British Columbia. During her excellent adventure, the female golden eagle flew 1,744 miles in August 2012 alone. She had previously ticked off more than 1,500 miles in July 2012.
She eventually returned, but it's is a good example of a trend researchers are seeing of young eagles wandering rather than looking for a territory of their own to raise their chicks.
"It seemed like she had been thinking about breeding and then just took off," Slater said. "It was like she was thinking, 'There is no food here. I'm going to Canada.' "