CAMBRIDGE -- High overhead, in an aerial pas de deux, two large birds swayed on the air currents. I focused the binoculars to make sure.
Yep. A couple of bald eagles.
In a dead tree not far away, a golden eagle sat perfectly still, surveying the surroundings.
Nearby, a great blue heron moved stealthily near the muddy embankment. Pausing for a second, it suddenly dipped its head and plucked a perch out of the ankle-deep -- do herons have ankles? -- water.
Elsewhere, ospreys hovered, Canada geese floated, black ducks paddled and red-winged blackbirds balanced on the tips of tall grasses.
It doesn't get much better than this.
If you're traveling on the Eastern Shore, it's definitely worth your while to spend a few hours at the Blackwater National Wildlife Refuge, about 12 miles south of Cambridge.
"I've been in eight states and 24 national wildlife refuges, and I've never been anywhere where I've seen more watchable wildlife," said Glenn Carowan, the manager of Blackwater, which is administered by the U.S. Fish and Wildlife Service.
The reason, as real estate agents like to say, is location, location and location. Blackwater is in the middle of a peninsula that juts into the Chesapeake Bay, providing a habitat to support myriad birds, especially waterfowl.
From whistling swans and snow geese that turn the ground white to turkey vultures that dot the sky with black, from colorful orchard orioles and barn swallows that flit about to soaring eagles and hawks, the nearly 17,000 acres of Blackwater provide a haven for birds, those just passing through and those that have found a permanent home.
The official bird list has 252 species, among them some rare sightings. Last year, Mr. Carowan said, a white pelican spent some time. Once in a great while a few white-fronted geese will land. Grebes and snowy owls have been spotted, and unusual blackbirds and sparrows have been seen. Endangered species such as the peregrine falcon and red-cockaded woodpecker also have been recorded.
The refuge, though, is perhaps best known for the bald eagle. Outside of Florida, Blackwater is the center of the largest nesting density of bald eagles in the eastern United States.
Historically the refuge has had peaks of about 40 bald eagles, but in the last two years as many as 89 have been spotted. During the last two summers officials have counted six nests, each with two young.
Sightings are common. I've seen bald eagles in all seasons, hanging out in trees, fishing and flying leisurely in circles. On one of my visits a bald eagle had moved into an osprey nest atop a man-made pole. It sat there -- about 30 yards from the paved road that winds through the refuge -- causing a traffic jam as visitors stopped their cars to gawk.
Conditions at Blackwater are ideal for eagles. Mature pine trees provide protection in the winter, remote islands have trees for nesting, the shallowness of the Blackwater River is conducive to fishing and the food resources are excellent.
Much of the diversity in habitat that draws the eagles lures the other birds that annually drop in at Blackwater, some to take up permanent residence. To supplement the natural resources, refuge personnel plant about 400 acres of crops for the birds.
The largest population is Canada geese, which begin arriving from the north in large numbers in late September, peaking about the third week of November. Numbers have fluctuated greatly in the 60 years since the refuge was established with an acquisition of 8,600 acres. At that time just a few hundred geese used the refuge. As the government bought more land and made a concerted effort to attract ducks and geese along the Atlantic Flyway, numbers of geese peaked at about 100,000. Today XTC about 35,000 geese and 17,000 ducks -- 20 duck species have been counted -- stay at Blackwater during the height of fall migration.
But it makes no difference when you go -- you're sure to see some activity. In the winter there are great horned owls, some shore birds and bluebirds. Spring brings the majority of migrant marsh birds. Summer insects are followed by kingbirds, swallows and flycatchers. In the fall, egrets and herons gather until the cold weather pushes them out, and songbird migration peaks.
The refuge has a paved, 5-mile wildlife drive that passes freshwater ponds, woods, fields and marsh. Short walking trails cut through the woods and along the marsh. Bicyclists are welcome along the drive, or can take a 20- or 25-mile loop around the vicinity. (Maps and other literature are available at the visitors' center.)
In addition to the extensive bird population, numerous mammals call Blackwater home: raccoons, otters, skunks, white-tailed deer and Asian sika deer. Before its designation as a refuge, most of the marshland along the lower Blackwater River was managed as a fur farm, with muskrats the primary catch.