Just before an early class last term, as I was twittering on about weekend bird-watching delights, one of my more earthbound students piped up: ''Why watch a bird?'' To this I responded with a devastating ''Well . . . ah . . . well . . . there are lots of reasons . . . lots of 'em . . .,'' at which point the belltower chimes rescued me from filling in the blanks.
Here's what I would have said, if I had thought fast enough.
First of all, I don't know why people in general watch birds; all I know is why I watch them. And I find watching birds relaxing.
Bird watchers spend a lot of time waiting, waiting for the redstart, heard but not yet seen; waiting for the shearwater, now just a comma on the Atlantic horizon, to move close enough to be noted as a ''Manx''; waiting three hours for a bald eagle at Cobscook Bay to pass within the range of the spotting scope. It's relaxing simply watching birds being birds - to follow the cardinal from feeding ground to nesting site, and back, and forth, and back, or to root for the kingbird's spirited defense of his airspace against a crow. Nope, I'm not just idly lolling here under this fir tree, I'm dutifully waiting for the great horned owl to return to his spring perch - one of these days.
I also enjoy the adventure of discovery in bird watching. I enjoy the challenge of naming my next-tree neighbors. More recently than I like to admit, I checked off my first black-capped chickadee - the Massachusetts state bird no less, a bird I probably tripped over as a child but never really saw. And at the seashore, before I knew better, I had a silly debate with my husband about whether a sandpiper strolling along the edge should be labeled ''solitary'' because it was alone or ''spotted'' because we had spotted it.
I identified my first red-winged blackbird by trilling (quietly) an imitation of the call in my field guide and matching it to the ''tee-err'' and ''konk-la-ree'' drifting from a nearby swamp. The naive joy of recognizing common birds passes with the efficiency of the watcher, but the pleasure of knowing them by name somehow carries on, making the world more familiar, more comfortable.
I feel a kind of rightness in things when the May warblers festoon the trees at Mount Auburn Cemetery, when the osprey returns annually to its South Dartmouth platform for nesting, when the woodcock dances its showy courtship ritual, or when hundreds of migrating hawks come kettling in spirals over our September lookout at Mt. Wachusett. Birds have a sense of the rhythm of things, and, if we move to the right tempo, we get to share the action - at least with binoculars. Birds remind us that the beat goes on quite well with or without us. They help us see that we are all a part of the system.
Maybe it was this lesson that led me to another while watching birds. It's impossible, for example, to visit the wintering site of the whooping cranes at Aransas National Park in Texas without confronting the need to take good care of them. Here their last small community shares a sparse bit of this earth with oil barges, rigs, and space-shuttle enterprises.
Bird watching has at the same time given me an excuse to see some faraway places with strange-sounding names. At Machias Seal Island near Maine, puffins seem to pose for pictures; at Cap Sizun in Brittany, kittiwakes chorus by the thousands, and near Skellig Michael off the coast of Ireland, grandstands of gannets nest in tiers on the rocky cliffs. Sitting in our jeep on Hippopotamus Point at Kenya's Lake Nakuru, we saw so many birds so fast we couldn't keep up with the IDs. ''Sacred ibis to the left.'' ''Sacred ibis to the left . . . check.'' ''Marabou stork to the right.'' ''Marabou stork to the right . . . check.'' ''Pink-backed pelican front and center.'' ''Pink-backed pelican front and center? Pink-backed pelican?'' ''Front and center . . . check!'' I love visiting sites where it's impossible not to see a bird.
It isn't necessary for me to go far, though, to find birds worth the watch. In fact, they have often come my way. Seven years ago, a Ross's gull, a rara avis from Alaska and Russia, stopped for a rest at a boatyard in Newburyport, drawing me from Cambridge and eager ''life-listers'' from hundreds of miles away. The winter before last, in Gloucester, a snowy owl posed sunlit for a half hour on an icy pier. He stared at us, and we stared back; he then turned slowly and stretched his wing and finally his talon feathers as if in an avian fashion show. At Mount Auburn one evening last year, I looked up a tree trunk only to see it looking back at me. A tiny hole in the tree framed a tiny screech owl face, a face on unblinking alert. I gave in first.
But the bird that has made me happiest so far was a local blackcapped chickadee. Early this spring in Ipswich, he landed on a rhododendron bush beside me. He looked expectant, so I put my finger out for him to perch, an offer that he took, settling there for a full minute. I had heard of a crow marching across a sleeper's pillow and of a bluejay tapping at a windowpane for breakfast, but I had never been so ready to believe that birds sometimes like to commune with us.
I have other reasons, too, for watching birds. They are, after all, beautiful - the tanager in the treetop, the great blue heron on the wing, the robin on the lawn at sunrise. The bird watchers themselves are basically a pleasing flock, usually good for sharing a ''find'' or appreciating yours.
Then there are the reasons I don't yet know.