Whip-poor-will – Familiar Nightjar
A Vociferous Bird Often Heard and Rarely Seen
The Whip-poor-will, a nightjar of North and South America, is a night bird but it's still well known within its range because of its distinctive call.
The Whip-poor-will, Caprimulgus vociferus, is a migratory night bird of the Americas. It breeds in southern areas of central and eastern Canada, the northeastern United States, southwestern United States, and in Central America. Though its nighttime habits and excellent mottled brown camouflage make it difficult to see, it is often heard calling its name over and over, seemingly endlessly, at dusk and dawn.
The Whip-poor-will frequents open forests, preferring deciduous trees. Pairs usually raise two chicks, with the eggs laid on leaves on the forest floor without the benefit of a nest. Chicks begin to move about quickly and leave their exposed birthplace soon after hatching.
One of the disappearing common birds of North America, Whip-poor-wills have declined by 57% in the last forty years. National Audubon identifies habitat loss as an important factor for the species: fire prevention in deciduous forests and human development encroaching on forest blocks. Programs of gypsy moth control may also have limited the food supply.
Here are some interesting facts about the Whip-poor-will and some related nightjars:
- Whip-poor-will breeding coincides with the full moon in late spring, when insects are plentiful and hunting is easy. The female lays eggs around the time of the full moon when she is well fed and healthy; the eggs hatch at the next full moon, when it's easy for the adult birds to catch insects to feed their young; and the young birds are independent by the next consecutive full moon, when it's easy for them to find their own food.
- Whip-poor-wills are thought to migrate individually; however, they are so well synchronized that they tend to arrive in the same place at the same time, giving the impression that they are traveling in flocks.
- Nightjars have a structure in the eye called the tapitum lucidum. This structure holds tiny oil droplets that allow the retina of the eye to absorb more light, giving the birds superior vision at low light levels. This makes it possible for nightjars to hunt for the abundant insects that appear at dusk and dawn, and on moonlit nights—they watch for flying insects silhouetted against the backdrop of the night sky.
- Nightjars have rictal bristles—long stiff bristles that form a comb overhanging the side of the upper beak. The purpose of rictal bristles is uncertain but they may protect the birds’ eyes from large struggling insect prey, or they may function as a net to help catch insects.
- The European Nightjar is often called a goatsucker because of an historical (incorrect) belief that the birds sucked milk from the teats of goats.
- The Common Nighthawk, often seen wheeling and catching insects at dusk over North American cities, is a member of the nightjar subfamily Chordeilinae, and is one of the few nightjars that has adapted to life in human communities.
- The Common Poorwill uses torpor to hibernate through the winter. This bird can lower its body temperature and suspend activity for more than three months when the weather is cold and insects are scarce.
Read about other familiar North American Birds in Decline:
Eastern and Western Meadowlark
The Fate of the Bobwhite Quail
Sources:
Audubon. “#17 Common Bird in Decline Whip-poor-will (Caprimulgus vociferus).”
Elphick, Jonathan ed. Atlas of Bird Migration. Buffalo: Firefly Books, 2007.
Kaufman, Kenn. Birds of North America. New York: Houghton Mifflin, 2000.
Perrins, Christopher ed. Firefly Encyclopedia of Birds. Buffalo: Firefly Books, 2003
