For the last two weeks, I've stepped outside at dusk each night for about 30 minutes and listened.

Spring peepers sang almost constantly, and occasionally I heard the tremulous whistle of an eastern screech owl and the hoots of barred and great horned owls. But my target was a whip-poor-will. A neighbor about four miles away heard one recently, so I was hopeful.

Only three times over the last 20 years have I heard the serenade of a whip-poor-will here on the ridge. The bird is a name-sayer -- "whip-poor-WILL" -- with emphasis on the last syllable. Sometimes males sing constantly for 20 to 30 minutes, so they are difficult to miss.

Readers, especially at this time of year, tell similar tales. They recall being sung to sleep by calling whip-poor-wills and wonder what has happened to them. I've already received a dozen such letters this year.

Because whip-poor-wills are nocturnal and of no commercial value, they have been poorly studied. Population estimates are based on breeding bird counts and anecdotal reports. Though people like me who rarely hear whips fear that their numbers have seriously declined, reports from other areas suggest otherwise. My mail, for example, indicates that in southeastern Ohio and mountainous areas of West Virginia and Pennsylvania, whip-poor-wills are still commonly heard. So perhaps their distribution is spotty and local.

I fear, however, that whip-poor-wills suffer, at least in some places, from poisoning by pesticides. They eat flying insects almost exclusively and winter in Latin America, where pesticides are less rigidly controlled than they are here in the U.S. I'd love to continue to hear from readers who hear whip-poor-wills regularly.

A description of whip-poor-wills is unnecessary because they are rarely seen in good light. They spend their days nestled on the forest floor where their cryptically colored bodies blend in perfectly with the leaf litter, or perched lengthwise overhead on a horizontal branch.

At dusk, whips come to life and earn their living by snatching moths, beetles and other night-flying insects from the air. Their huge gaping mouth, surrounded by a ring of specialized feathers called rictal bristles, becomes an efficient aerial net for capturing insects on the wing.

After a male attracts and courts a female, she lays two mottled eggs directly on the leaf litter. She builds no nest. The female alone incubates the eggs for about 20 days, and 20 days later the young whip-poor-wills can fly and begin learning to fend for themselves.

Whip-poor-wills are members of a family of birds variously called goatsuckers or nightjars. The misconception that these birds suckle goats dates as far back as Aristotle and is known from many cultures. Presumably, some species have been commonly seen roosting or flying near resting goats, conclusions were jumped to, and a myth was born. The term "nightjar" stems from the songs of these birds that "jar" the night.

A similar bird, the chuck-wills-widow, also occurs in the southeastern states, though chucks sometimes wander as far north as New York and Michigan. Chuck-wills-widow, also a name-sayer, sings a four-note song, with the accent on the third syllable. When I lived in Oklahoma, I often heard both species singing simultaneously, and though similar, the songs are easily distinguished.

A third and much more abundant goatsucker, the common nighthawk, occurs across most of North America. While whip and chuck inhabit wooded areas, nighthawks prefer more open habitats such as farmland, grasslands, meadows, and even cities. In fact, the best place to see nighthawks is at evening sporting events illuminated by stadium lights. They sweep the sky as they forage for flying insects attracted to the lights.

Nighthawks can be identified by both sight and sound. They are dark gray with prominent white patches near the tips of the wings. In flight, they often vocalize. The sound is a nasal "peent" similar to the song of the American woodcock. Watch and listen for nighthawks at evening baseball games and early-season football games.

While I enjoy seeing and hearing nighthawks almost every day, I wish I could say the same for whip-poor-wills. The woods seem incomplete without them.