For a bird most often associated with misty forests and snow-capped peaks, there sure are a lot of bald eagles at Lake Mead.
Biologists spotted 163 of them during their recent annual count at the 1.5 million-acre national recreation area.
That’s the second- highest total ever, and it might have been even higher if not for strong winds that chased the survey boats off Lake Mohave during the Jan. 16 count.
“We were very, very close to a record number here,” said Ross Haley, a wildlife biologist for the National Park Service at Lake Mead. “At one time we counted 20 birds in the air above us.”
Six years after America’s iconic bird emerged from the endangered species list, its numbers continue to soar at the lake and across the nation.
And there is mounting evidence that bald eagles are staying longer – possibly even settling down – at the recreation area, which used to serve as little more than a pit stop during longer migrations from the Pacific Northwest and Canada.
A pair of eagles has nested in Black Canyon for each of the past three years, and survey crews counted 21 eagles in the same general vicinity last week, “which is way more than usual,” Haley said.
Most of the eagles spotted at Lake Mead are juvenile birds, still lacking the distinctive, snowy white hoods they get as they reach sexual maturity.
Experts can’t say why more eagles seem to be stopping at Lake Mead and staying longer than before, though there is plenty to attract them, namely fish, high places to perch and lots of open water.
The simplest explanation is that there are more bald eagles here because there are more bald eagles, period.
When the birds were declared endangered in 1967, widespread use of the pesticide DDT and other factors had reduced their numbers to fewer than 500 nesting pairs in the lower 48 states.
The U.S. Fish and Wildlife Service now estimates there are more than 150,000 bald eagles nationwide, including roughly 70,000 outside of Alaska.
Biologists have been counting eagles at the Lake Mead National Recreation Area since the early 1980s, but the count method has been standardized and refined over the past decade to improve the quality of the data.
This year’s count, timed to coincide with similar eagle surveys nationwide, was conducted by the park service with help from the U.S. Bureau of Reclamation and the Nevada Department of Wildlife.
The daylong effort involved more than 30 staff members and volunteers in eight boats sent to patrol designated sections of the reservoirs above and below Hoover Dam.
The highest concentration by far was found along the Overton Arm at the north end of the park, where the Virgin and Muddy rivers empty into Lake Mead.
Haley said the numbers are usually higher there, but this year they were off the charts – 93 eagles, almost double last year’s record count for that area.
Haley and company are not quite sure why the eagles seem to prefer the Overton Arm, but it could be because there is more waterfowl for them to eat in that part of the lake.
So why go to the trouble of counting bald eagles now that they are safely out of danger of extinction?
Aside from being the national bird, it is also a proven indicator species for disturbances in ecosystems, especially aquatic ones.
As Haley explained it, eagles feed on large fish that feed on smaller fish that feed on even smaller fish, so any chemicals that find their way into lakes and streams tend to accumulate as they move up the food chain.
Just as bald eagles helped us recognize the dangers posed by DDT, they could clue us in one day if some other chemical we release into the environment begins to take a toll.
“We’ll probably be able to see it in the eagle population before it starts killing us,” Haley said.
“Miners didn’t take canaries into coal mines because they liked to hear them sing.”
Contact reporter Henry Brean at firstname.lastname@example.org or 702-383-0350.