Air Date: Week of September 3, 1999

It’s not only during the daytime that we can observe the seasonal migration of birds. Commentator Sy Montgomery listens to the voices of migratory birds that can be heard in the night.

Transcript

CURWOOD: Migration time has begun, And we mostly notice it during the day. The afternoon sky can carry the V-shaped formations of Canada geese, And it's possible to spot hawks passing over mountaintops at dawn and dusk. Most birds, though, pass by more subtly, And sometimes we don't see them at all. But they don't get by commentator Sy Montgomery. She lies awake and listens for their voices in the night.

MONTGOMERY: Half an hour after sunset, they begin moving in waves. Protected by the darkness, guided by the stars, millions of tiny song birds pass over our roof tops, flying invisibly through the night. The dark hides these fragile creatures from predators like hawks, who migrate by day. The evening's cool, stable air smooths their flyways. But to bird-watchers' frustration, night also shrouds the miracle of these songbirds' migration. But they can be clearly heard. Each species' call is as distinctive as its plumage. If you like awake on fall nights, and listen, you can hear their voices.

(Song birds call)

MONTGOMERY: Five thousand birds may fly through a one-mile cross-section in a single night. Flying in loose flocks, each bird spaced hundreds of feet from the next, they call to one another to stay in contact. Perhaps the calls serve as air traffic control, to keep birds who can't see one another from colliding. Or perhaps they call as we might whistle in the dark, to bolster their confidence during a dangerous and distant journey. Bill Evans, a researcher at Cornell's Laboratory at Ornithology, has been listening to these calls for the past 12 years. He knows the voices, And which belong to whom. He told me, you can live the journeys these birds are making, the miraculousness of it. You can visualize all those birds going over without seeing a thing.

These nocturnal calls are often quite different from the territorial songs birds sing in the spring. After more than a decade of careful listening, Evans has amassed a personal aural field guide. A series of mellow whistles tells him a flood of rose-breasted grosbeaks are passing through. Wood thrush migration calls sound somewhat like the chime of a bed spring. Swainson's thrushes sound like spring peepers. In this way, Evans has pioneered a major new technique to measure for the first time which species are migrating where and when. Using his technique, for the first time ornithologists may be able to map precise migratory times and routes for individual species, as well as monitor dips and rises in population.

I can't see in the dark with my ears as well as Evans can. But as I lie awake on fall nights, these soft voices speak to me still. They speak of timeless journeys. They speak of the unknown that lies ahead. They speak of tiny creatures with the faith to undertake great ventures. These are the voices of courage in the dark.

(Music up and under)

CURWOOD: Commentator Sy Montgomery lives in Hancock, New Hampshire. She comes to us from New Hampshire Public Radio.