Perched in the skeleton of a small tree, four bald eagles stare out at the waters of Lake Mead as a boat slowly motors by.
Three of the birds are youngsters, less than 5 years old judging from their mottled breasts and brown heads. The one perched highest in the tree is an adult, unmistakable in its snowy white hood.
They look a little like a junior high class on a field trip -- three awkward teens and their chaperone.
The eagles have landed once again at Lake Mead National Recreation Area, and they're back in impressive numbers.
The people on the boat can hardly believe what they're seeing through their binoculars.
"Four eagles in a tree," says Vanessa Truitt, who works for the National Park Service at Lake Mead. "There's something you don't see every day."
Adds park service volunteer Mike Thiessen: "It's a social network."
SNOWBIRDS NO MORE?
Five years have passed since America's iconic bird of prey was removed from the endangered species list, and its presence at Lake Mead appears to be growing.
Biologists have noticed that an increasing number of bald eagles are making the waters straddling Nevada and Arizona their winter destination, not just a pit stop on longer migrations from the Pacific Northwest and Canada.
"There's a lot more of them than there used to be. In the last five years, it seems like it's building up faster," says Ross Haley, a wildlife biologist for the National Park Service at Lake Mead for the past two decades.
At least a few of the birds like it so much they've decided to stay.
The harsh desert surrounding the nation's largest man-made reservoir is not considered prime breeding habitat for bald eagles, but that's just what one pair did last year.
"We had two adults and a young one flying around in Black Canyon all summer," Haley said. "It was the first documented successful nesting at Lake Mead ever."
Only 60 bald eagles were counted on lakes Mead and Mohave during surveys in 2001 and 2004. The annual count conducted Wednesday turned up 161 bald eagles at the 1.5 million-acre recreation area east of Las Vegas.
It wasn't a record -- that was set last year at 177 -- but it's close enough, especially in what some experts thought might be a disappointing year.
Haley certainly expected this year's number to drop -- maybe significantly -- because of unusually mild weather across the West so far this winter. With plenty of fishing grounds still free of ice to the north, he figured some eagles might not have made the trip yet.
OFF TO A SLOW START
As the survey gets under way, it looks like Haley might be right.
Almost an hour has passed since he steered the boat away from Echo Bay Marina, and not a single eagle has shown itself.
Haley, Truitt, Thiessen and park service intern Tiffany Pereira scan the shoreline as the boat putters along at less than 10 mph.
The first sighting of the day comes roughly six miles and 60 minutes from the dock: a juvenile bald eagle about the size of a fire hydrant perched on a distant ridge. Backlit by the sun, it looks like a lump of rock or a cactus. Then it turns its head.
The sightings gradually build from there as the boat winds its way along a shoreline pushed outward by a 40-foot rise in the surface of Lake Mead over the past year.
The higher water allows the crew to venture farther north and west than they did during the previous survey.
The added distance pays off spectacularly just before noon, when Haley steers the boat toward a promising bluff near the mouth of the Virgin River. The ridge high above the water is dotted with eagles -- five in all, including three juvenile birds that soon take wing and begin to soar and play in a loose spiral overhead.
A few minutes later, the survey crew spots five more eagles clustered together, four of them perched in the same small tree.
A BIRD WORTH WATCHING
Research suggests there may have been as many as half a million bald eagles soaring over North America before European settlers descended on the continent.
By the time the birds were declared endangered in 1967, six years before passage of the Endangered Species Act, their numbers had tumbled to less than 500 nesting pairs in the lower 48 states.
The bald eagle's brush with extinction was blamed in part on habitat loss and the use of the pesticide DDT, which collected in the fish it ate and disrupted the bird's fertility and egg production.
Today, there are thought to be about 70,000 bald eagles in existence, with roughly 80 percent of them concentrated in Alaska and British Columbia, Haley said. "This is a big success story for the Endangered Species Act."
Eagle surveys at Lake Mead National Recreation Area date to 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 survey was conducted by the park service with help from the U.S. Bureau of Reclamation, Nevada Department of Wildlife and other groups. It was timed to coincide with similar eagle counts nationwide.
The dawn-to-dusk effort involved 32 staff members and volunteers in eight boats sent to patrol designated sections of the reservoirs above and below Hoover Dam.
There was talk that the surveys might stop once the bald eagle was safely off the endangered species list, but Haley said there is good reason to keep an eye on a bird perched so patriotically at the top of the food chain.
"In my opinion, bald eagles have proven themselves to be good indicators of general environmental health," he said. "This time it was DDT, but there are thousands of chemicals that humans use that have the potential to accumulate in the environment."
Lake Mead is a sheet of mirrored glass on this windless and unseasonably warm day.
In keeping with past surveys, Haley's route to the top of the lake's Overton Arm yields the greatest number of bald eagles: 49 in all, including 20 adult birds.
He thinks it might be the most they've ever seen in there.
The survey crew also counts 24 burros, one coyote and, in what may be the rarest sighting of the day, a pair of muskrats swimming in a forest of flooded salt cedars near the mouth of the Muddy River.
They also log at least 10 rogue cattle trespassing in the national recreation area.
They don't bother to count all the coots, ducks, geese and herons that populate the lake, though the crew does pause several times to watch peregrine falcons dive through flocks of water birds with murderous speed.
The final eagle of the day is spotted on a low rock near the water in a darkening cove not far from Echo Bay Marina. As the boat approaches, the adult bird spreads its 7-foot wing span and rises quickly through a patch of fading sunlight, disappearing effortlessly over a nearby ridge.
Truitt jots it down, one more for the record books.
Contact reporter Henry Brean at firstname.lastname@example.org or 702-383-0350.