Whip-poor-wills are medium-sized nightjars. They range from 22 to 26 cm in length and from 43.0 to 63.7 g in mass. They have a large, flattened head, large eyes, small bill with enormous gape, and rounded tail and wings. The bill and iris are dark brown while the legs and feet are also brownish. The feathers are grayish brown with darker streaks and broad black stripes on the crown. There is a white stripe across the lower throat. The wings are covered in grayish brown feathers with tawny and buff colored spots and speckles. Females are almost identical to males except that they have a thinner stripe on their throat and a more pale color with brown for the outermost tail feathers instead of white. Females are also slightly browner in general color.
Whip-poor-will hatchlings are completely downy with a yellowish brown color. Young males are similar to adult males, except the crown has black spotting instead of streaking. Young females are similar to young males, except their outer tail feathers don't contain white.
Whip-poor-wills can be distinguished from other members of the nighthawk and nightjar family by their white throat band, relatively small size, and brownish color. Whip-poor-wills can be distinguished from Chuck-will's-widows by their smaller size, less reddish color, and smaller white markings on the tails of males.
Whip-poor-wills are found in North America during the warm months of the year, reaching from central and southeast Canada to parts of southern Mexico. They are not found in the western United States except for small populations in Arizona, Texas, and New Mexico. Whip-poor-wills are also found in Mexico and Central America during migration and winter.
Whip-poor-wills are usually found in dry deciduous or mixed woodlands and some pine-oak woodlands. They prefer to live in young second growth forests, especially dry woods near fields and other open areas. The amount of openness in the forest seems to be more important than the type of trees that make up the forest. Shade and small amounts of ground cover are also important in whip-poor-will habitat. During migration they are also found in forested habitats. They are usually found in lowlands but can be found from sea level to 3,600 meters elevation.
Whip-poor-wills are thought to be monogamous. There is little known about whip-poor-will courtship displays. Females may try to get the attention of males by strutting on the ground with a lowered head, outspread wings and tail, and while making a guttural chuckle. Males respond by approaching the female, circling her, and moving their bodies up and down. If the female flies away, the male may not follow. The male may also try to approach the female by using a tail-flashing display.
Whip-poor-wills breed twice per year, from May through June, usually laying 2 eggs per clutch. They lay eggs on the ground usually beneath trees, bushes, or fallen trees branches near open areas. Most nests are depressions in leaves, pine needles, or bare ground. Eggs hatch after about 19 days. Time to fledging is about 17 days. Little is known about when whip-poor-wills have reproduce, but it is thought to be 1 year of age, the average for the nighthawk and nightjar family. Whip-poor-will reproductive cycles are synchronized with moon cycles, resulting in better moonlit nights when foraging to feed their young.
Both male and female whip-poor-will adults incubate the eggs, starting with the laying of the first egg. Both parents feed their young, beginning right after hatching. While one parent is finding food, the other is protecting the nest. Whenever the returning adult comes back to the nest, it regurgitates insects to both young. Young whip-poor-wills have been known to accept food from parents at 30 days of age. Whip-poor-will hatchlings are able to avoid predators without parental care from a fairly early age.
Little information is known about the lifespan of whip-poor-wills. Tagged wild whip-poor-wills have been known to live up to 15 years. Most causes of mortality occur when birds are very young or as eggs. There is some competition with related species, such as Chuck-will's-widows that might reduce their lifespan.
Whip-poor-wills fly slowly and noiselessly. They usually glide and can take off nearly vertically. They waddle when they walk and can make short hops. They are nocturnal animals that move very little at dusk or dawn. They typically roost in tree branches close to the ground. Whip-poor-wills are generally solitary but may form small flocks during migration. (Cink, 2002)
Whip-poor-wills migrate to the southern tip of Florida, Mexico, and Central America in early September and October. They return to breeding sites from late March through May.
Little is known about the home range but some have been known to have territory sizes up to 111,000 square meters. (Cink, 2002)
Whip-poor-wills are known for their three tone calls, sounding like "whip-poor-will", for which they are named. This call is usually given by males to establish territories. The "quirt" is a soft call that communicates excitement or stress, it is usually used by wintering, territorial birds. A "growl" is a fluttering sound used when two territorial individuals meet. The "hiss" is a repeated loud call used when predators are near. The "cur" is a guttural chuckle, often given during courtship or at other times by nesting birds.
Whip-poor-wills fly at night to catch their prey, they mostly eat night flying insects, but also eat insects that don't fly. They are known to eat moths, mosquitoes, flying beetles, ants, grasshoppers, and crickets, but moths make up most of their diet.
Losses from predation are mostly of eggs and young birds because ground nests are extremely vulnerable. Predators such as skunks, raccoons, coyotes, red foxes and snakes prey on the eggs and young. To protect their young, adult whip-poor-wills fake an injury by flopping on the ground near the nest and in full view of the predator, called the "Broken Wing" display. This is performed until the predator is not in view of the eggs or young and the adult then displays on a perch above the ground. Whip-poor-wills are patterned in brown, helping them to blend in with their forest floor surroundings. They are also nocturnal, both of these help to protect them from predation.
There are no known adverse effects of whip-poor-wills on humans.
Whip-poor-wills are insect eaters, usually living near open, agricultural areas. It is likely that they help control insect populations that affect humans. Because whip-poor-wills nocturnal and difficult to observe, they have no other known interactions with humans.
Whip-poor-wills have a large global population, estimated at 2,100,000 individuals. Although the population seems to be declining, it is not expected to reach the threshold for population decline that would put it on the IUCN Red List of Threatened Species. This species has an IUCN Red List status of least concern. (Ekstrom and Butchart, 2004; Ekstrom and Butchart, 2004)
The species name, vociferus, is Latin for "voice-carrying" or "noisy." ("Goatsuckers Whip-poor-will, Caprimulgus vociferus", 2000)
Tanya Dewey (editor), Animal Diversity Web.
Robert Duszynski (author), Kalamazoo College, Ann Fraser (editor, instructor), Kalamazoo College.
2000. "Goatsuckers Whip-poor-will, Caprimulgus vociferus" (On-line). Georgia Wildlife Web. Accessed October 11, 2006 at http://museum.nhm.uga.edu/gawildlife/birds/caprimulgiformes/cvociferus.html.
2001. Nighthawks and Nightjars. Pp. 348-351 in C Elphick, J Dunning, D Sibley, eds. The Sibley Guide to Bird Life and Behavior. New York: Alfred A. Knopf, Inc.
Cink, C. 2002. Whip-poor-will (Caprimulgus vociferus). Pp. 1-20 in A Poole, F Gill, eds. The Birds of North America, Vol. 16 No. 620. Philadelphia, PA: The Birds of North America, Inc.
Ehrlich, P., D. Dobkin, D. Wheye. 1988. The Birder's Handbook. New York: Simon and Schuster Inc.
Ekstrom, J., S. Butchart. 2004. "The IUCN Red List of Threatened Species" (On-line). Accessed November 05, 2006 at http://www.iucnredlist.org/search/details.php/48656/summ.
Peck, G., R. James. 1983. Breeding Birds of Ontario Nidiology and Distribution Volume 1: Nonpasserines. Toronto, Canada: The Royal Ontario Museum.