It may be significant or then it may not, that the city of Washington, which trembles with anticipation at each eyclical surge in the affairs of state, tends to sleep through eyclical wonders in the affairs of nature.

Thus we find ourselves now teetering on the very brink of the peak spring bird migration, once again unprepared.

If some ruby-throated humming-bird, all three inches of him, flies here each May all the way from Panama, shouldn't we care?

If a seabird called the sooty shearwater makes it all the way from Tierra del Fuego to the waters off Ocean City, isn't that as important in the scheme of things as, say, the President's energy program?

Chandler S. Robbins thinks so, but then Robbins, a gentle man of 58 who heads the Migratory Non-Game Bird Studies section of the U.S. Bureau of Sport Fisheries and Wildlife looks on life with a sense of wonder undimmed by either his 32 years in the federal government or his Harvard degree in physics.

"It may not strike everyone as earthshaking, but it's exciting all the same," he said. "Just think - all the way from South America!"

During the next two weeks, as they do every years in early May, more different kinds of birds will pour through the area from the Virginia foothills to the Maryland coast than are visible probably any other time or place in the country.

Millions of birds will be here from the rufous-sided towhee to the mute swan, from the semi-palmated sandpiper to the common crow. The purple martins will be up from Brazil, the white-eyed vireos in from Mexico and the Cape May warblers back from vacation in the West Indies.

Many of the birds will be just passing through - long-distance commuters like bobolinks on their way from Argentina to nest in Maine. Others, like some of the myrtle warblers and hermit thrushes, will be here to nest and still others, like some of the sparrows and robins, live in the area all year long.

"In other times and places you may have just as many different birds present, but you can't find them," Robbins said.

"They may be flying through at night or hidden in thick foliage. In the fall, when they're moulting, they're less colorful and consequently harder to spot. And they're not singing then. Many species are identified almost entirely by song," he said.

But in early May, the birds hit Washington in full color and song; better dressed than most of the city's other spring visitors, and more harmonious. The leaves aren't full on the trees yet and avian privacy remains vulnerable to the binoculars of the respectfully curious. It is, says Robbins, "the World Series of birding."

More than one-third of the nation's 645 resident and migrating bird species may be present here during the period. An expert birden or well primed for the challenge with rest, organization, exact planning and perfect weather, can hope identify 200 separate species in a single day.

Such a feat involves springing out of bed about 3:30 a.m. to hear the songs of night-flying sparrows; combing the streamside thickets and meadows in early morning for the fly-catchers, warblers, thrashers and wrens: racing to the Chesapeake Bay or coastal marshes in early afternoon for water birds, and then stalking the night woods to listen for whippoorwills and owls.

The 200-bird day, however, remains the perfectly pitched no-hitter of bird-watching's World Series - aspired to by many but achieved by few.

Robbins has been birding since he was 12, spends all his work days studying birds, goes birding on weekends and has written a much-used field guide to bird identification."But my best day was only 189," he said, rather wistfully."So many things have to go just right . . ."

It's less the competitive challenge of birding that captivates Robbin, however, than the mysteries of birds themselves, particularly how and why they migrate such tremendous distances.

"Some things we understand," he said. "Many insect eaters fly south, not because of the cold alone, but because they can't find insects in the cold. A few species, like tree swallows, have adapted to eating bay-berries when they can't get insects and they winter on the Eastern Shore. But the others fly to Mexico or Central America to find food.

"All it takes is a look at the map to see why they don't stay there (Central America) all year: the continent gets very narrow. They need more space for breeding and nest building. So they fly north in our spring to a wider land mass."

But no one really knows how they find their way.

"We know some overland birds like hawks follow mountain ridgelines an d some coastal birds obviously follow the shore. And experiments with birds under artificially altered skylines indicate that some night fliers apparently use stars."

But other sea birds migrate under overcast skies, apparently by instinct, to some tiny island where they were born, thousands of miles away from any landmark.

And while some birds, like black-birds, migrate in flocks, other travel singly, often prededed by young birds that have never migrated before but somehow find their way.

Among the solo fliers are the hummingbirds, Robbins said.

"There's a place on the Virginia Eastern Shore near Kiptopeke were you can stand in the fall and watch the hummers taking off south over Chesapeake Bay," Robbins said. "They come past you every few minutes, flying about 4 feet off the ground, making maybe 30 miles an hour. They all seem to follow the same track. They'll go down the coast and then fly straight across the Gulf of Mexico to Panama, nonstop. God only knows how they do it."

Other migrating birds, flying from Canada to South America, take a sort of Great Circle route over the ocean for thousand of miles rather than follow the coast.

They show up in flocks on the radar over Bermuda. By all rights they should stop there for food and water, but they don't. They just fly on.

Then there are other birds, like cuckoos and gray-cheek thrushes, which show up periodically in the British Isles, confounding the experts who know they couldn't possibly have flown the Atlantic.

All of this, of course, is not without cost. Only 1 in 10 baby songbirds survives to adulthood, and only about 50 per cent of each year's birds make it through migration to the next year.

A few songbirds may survive as long as five years, but nature makes up for the high mortality rate among small birds with a higher bith rate. A large bird like an albatross, which may live as long as 30 years, lays only one egg a year, while the smaller, more vulnerable species may hatch several clutches of four to six eggs in a single season.

And while the swallows may all come back to Capistrano on the same day each year, migrating birds in the East follow a rougher timetable, often delayed for weeks at a time by weather or other factors.

A rough progression, however, persists, with some of the ducks and geese flying north in February, purple martins winging in March, the seed eating species like sparrows and blackbirds in early April, the warblers and thrushes in mid-April, and the heavy migration of most other species in early May.

The cuckoos are last, arriving in June. By that time some of the sandpipers have already laid their eggs far to the north and have started south again and the cycle is repeating. "There's almost always something going on with birds any time of year." Robbins said.

He paused in his explanation to gaze out the window of his office in the Patuxent Wildlife Research Center toward a flock of tiny sparrows swooping against the midmorning clouds.

"Look! The Chimney swift have arrived." he said. "Think of it! All the way from the Amazon!"