WOLF SWAMP - The wise old bird man has finished his morning's work, but still he will not leave the woods.
By 11 on a bright summer morning, eminent ornithologist Chandler S. Robbins, who turns 84 this month, has put the finishing touches on a survey of bird life in a Garrett County bog that he first studied more than 50 years ago. He has gathered fresh data for a new version of an atlas of Maryland's birds, which he edited. And he has spotted a song sparrow's nest in a rotting stump on land that he bought in the 1950s but rarely has time to visit.
His companions are heading for the car. But Robbins stands motionless on the bank of a slender stream, transfixed by the liquid song of a hermit thrush perched in an oak.
Robbins has heard the melody thousands of times, but it has not lost its power to enchant him. He adjusts the volume on his hearing aids.
Head atilt, he listens for several minutes, then reluctantly turns to go.
"Well, you hate to walk away from a singing hermit thrush," he says, moving into the loose-limbed stride that usually leaves younger hikers stumbling in his wake.
Robbins, who joined the Interior Department's Patuxent Wildlife Research Center in 1945, is a man transparently in love with his work.
He has "almost a childlike love of birds, and it's remarkable that he's never lost that. It's pure," said independent naturalist Daniel Boone, his one-time student and longtime friend.
Robbins has lured several generations of Americans to share his passionate pursuit.
He is the author of a classic field guide that helped make bird-watching one of the nation's most popular pastimes, enjoyed at least occasionally by about one in three adults.
He has also documented the decline of many of his beloved songbirds as the wild woods, meadows and marshes they once inhabited succumb to development.
In 1966, Robbins invented a continentwide survey of the birds that nest in North America. Experts say the Breeding Bird Survey, conducted each year by about 6,000 volunteer bird-watchers, helped create the modern conservation ethic.
"I would put the invention of the Breeding Bird Survey in this class of things that took place in the mid-1960s and early 1970s and triggered the awakening of North Americans to environmental consciousness," said John W. Fitzpatrick, director of the Cornell Laboratory of Ornithology. "It showed some of the patterns that people had begun to sense in the wind but couldn't put any numbers to ... that a significant number of birds were really getting scarce."
That knowledge inspired an international effort to save the birds - especially those that migrate between North and South America - by preserving the land where they spend summers and winters.
Now some of those birds are doing better, but others are not. The Breeding Bird Survey shows that since 1980 about 98 species have increased their numbers - but 114 are declining rapidly.
Robbins' long memory of a world richer in bird life occasionally casts a shadow across his sunny nature.
He has pored through birders' journals back to the 19th century. The old accounts are full of descriptions of "counter-singing" between males of the same species as they staked out territories and tried to attract mates.
Such contests, with competitors chiming in from every direction, are rare now.
"These birds don't have to sing," he said sadly. "There's only one."
Robbins began studying birds as a schoolboy in his Belmont, Mass., back yard. As a young researcher at Patuxent, he explored Maryland from the western mountains to the lower Eastern Shore.
In brief summaries of his travels, published in birders' magazines in the late 1940s and early 1950s, Robbins described a wild Maryland that was already in remnants:
"The last remaining virgin spruce bog ... The only tract of virgin Hemlock remaining ... A magnificent stand of undisturbed deciduous forest."
Most of the wild places he studied still exist - in some cases because of his work. Most recently he was instrumental in helping environmentalists win state protection for Belt Woods in Prince George's County, the "magnificent stand" of 400-year-old oaks, poplars and maples that he described in 1947.
The state steps in
About half the trees were felled to make wood veneer, said environmentalist Ajax Eastman of Baltimore. But in 1997, the state acquired what was left of Belt Woods to forestall construction of a subdivision where the last old trees stand.
Robbins also helped persuade the Maryland Ornithological Society to buy more than a dozen tracts of prime bird habitat. The result, said Boone, is "one of the best systems of private sanctuaries for birds" in the country.
"When I was a kid, I was completely focused on the birds and paid no attention to the habitat," said Robbins, "but it soon became apparent that if you don't have the habitat, you don't have the birds."