We rounded the bend on a wooded trail and suddenly found ourselves before a still, sunlit lake. ''Oh, this is lovely,'' a woman beside me trilled. ''It's like Shangri-La.''
For the record it wasn't Shangri-La or even Lake Titicaca, but an algae-filled pond in Central Park, New York, and I was on a morning bird walk conducted by the American Museum of Natural History. The woman's sense of euphoria may have been traceable to the rare crisp autumn weather or simply to the thrill of being out on a nature tour, however modest.
Such tours, whether into the urban wilds of your hometown or to far-off and unpronounceable places, are gaining in popularity as museums, institutions, and specialized travel agencies tap America's newfound interest in natural and offbeat forms of travel. While the American Museum of Natural History's cruise to the Galapagos Islands in pursuit of the masked and red-footed boobies means an investment of 11 days and more than $3,000, a quiet bird walk in Central Park runs $4 and will have you finished by lunch.
Stephen Quinn, a museum naturalist, leads the park tours on Tuesday and Thursday mornings in the spring and fall at the peak of bird migration, and although he also takes groups abroad on museum excursions, one gets the immediate feeling he is most at home in the city woodlands. As we plunged into that 840-acre human and wildlife sanctuary, Mr. Quinn surveyed the cloudless sky and said, ''Keep looking for hawks above the trees. It's a great day for hawks.''
There were perhaps two dozen birders along, each equipped with binoculars and many with field guides. Some obviously knew Mr. Quinn from previous excursions, and most knew their birds, rare and otherwise. Minutes after entering the park Quinn and some of his frequent followers were already exclaiming quietly over white-throated sparrows, ruby-crowned kinglets, and juncos in trees and shrubs that looked empty of any life to me.
But as we stood beside our Shangri-La - the sunlit lake - someone whispered, ''There's a cardinal.'' Quinn added, ''Yes, just above the bayberry,'' and I made my first positive sighting. Sharp-eyed naturalists can also see where birds have already been. Pointing to a tangle of weeds hanging from a high bough, Quinn said, ''That's the remains of the nest of a northern oriole, or what used to be called a Baltimore oriole.''
We were near a road surging with traffic, but now we turned away from the sounds of a city going to work and headed into a rich and mysterious birding zone, The Ramble. Without a blue-blazered guide like Mr. Quinn, one could easily get lost in The Ramble, an area of dense verdure, huge rock outcroppings, and crazily winding trails.
As we mounted some rude stone steps, the turrets of a dark Victorian castle appeared through the trees. Soon we were astride Belvedere Tower, an 1869 structure that is used as the recording station for New York City's infamous weather. There is a meteorological exhibit on the second floor of the recently restored tower. Its stone parapets provide a fine viewing spot for waterfowl on the pond below. We saw Pekin ducks, gulls, and mallards, nothing to cause a birder to reach for his field guide. Suddenly, looking heavenward, I made a fresh sighting.
''Just young gulls,'' Quinn said. ''But keep looking for those hawks.''
Heading deeper into The Ramble, I asked our leader what other exotic residents or migrants we could hope to spot. ''Well, last week we saw osprey and owls and herons,'' he said, ''and someone saw a raccoon and . . . whoops, whoops , hold it!'' Quinn stopped in his tracks. Then for five or 10 minutes we deployed around a patch of shaded woods watching a hermit thrush hop about the ground.
''You should come along in the spring,'' one of Quinn's frequent followers whispered to me. ''He knows the mating songs of the birds and can identify them even before he sees them.''
When the two-hour walk was up, we had spotted neither hawk nor heron, but no one felt cheated. Perhaps the high point came when an English-accented man named Tony, out on a free-lance birding trek but known to Mr. Quinn and a few others, uncovered a winter wren flitting about the brush. ''It's a very shy and elusive bird,'' Quinn said. ''You shouldn't miss it.'' Down on all fours, I caught a glimpse of the chocolate-brown bird jumping from twig to leaf like a tiny mouse.
Of course, more-exotic sightings are guaranteed to those who repair beyond their city borders on nature and wildlife tours like those offered by the American Museum of Natural History. Todd Nielsen of the museum's Discovery Tours department noted that a specialist accompanies each group, whether to the Galapagos in pursuit of the masked booby or on the trail of gorillas in the high forests of Rwanda, in East Africa. (For more information write Discovery Tours, American Museum of Natural History, Central Park West at 79th Street, New York, N.Y. 10024.)
Other nonprofit groups experienced in the field are the National Audubon Society, the Smithsonian Institution, the California Academy of Sciences in San Francisco, and the Field Museum of Chicago. Among specialized travel agencies, Society Expeditions (723 Broadway East, Seattle, Wash. 98102) and Questers Tours & Travel Inc. (257 Park Avenue South, New York, N.Y. 10010) will take you to the likes of the Amazon jungle and the Okefenokee Swamp.
If you need a warm-up tour, I can recommend the Quinn safaris of Central Park , hawks or no hawks.