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Caprimulgus vociferuswhip-poor-will

By Robert Duszynski

Geographic Range

Caprimulgus vociferus is primarily found in North America, reaching from central and southeast Canada to parts of southern Mexico. Caprimulgus vociferus is not found in the western United States except for small, disjunct populations found in Arizona, Texas, and New Mexico. Whip-poor-wills are also found in Mexico and Central America during migration and winter. (Cink, 2002)

Habitat

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 degree of openness in the forest seems to be more important than the type of trees that make up the inhabited forest. Shade and sparse ground cover are also key elements of whip-poor-will habitat. During migration, they can be found in low canopy levels of their migratory forest. They have a tendency to inhabit lowlands but can be found at elevations ranging from sea level to 3,600 meters. ("Nighthawks and Nightjars", 2001; Cink, 2002; Ehrlich, et al., 1988)

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.

  • Range elevation
    0 to 3600 m
    0.00 to 11811.02 ft

Physical Description

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. Plumage is 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. There is no seasonal plumage change. Females are almost identical to males with the exception of a thinner stripe on their throat and a more pale, clay color with brown for the outermost tail feathers, instead of white. Females are also slightly browner in general color. There is no known information on basal metabolic rates of whip-poor-wills. (Cink, 2002)

Whip-poor-will hatchlings are completely downy with yellowish brown color. Juvenile males are similar in appearance to adult males, except the crown has black spotting instead of streaking. Outer primaries and outer tail feathers are also narrower and more tapered compared to adults. Juvenile females are similar to juvenile males except their outer tail feathers don't contain white. (Cink, 2002)

In general, C. vociferus can be distinguished from other members of the Caprimulgidae family by the white band on its throat, its relatively small size, and its 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. They are distinguished from common pauraques and common poorwills, which are larger, have longer tails, and have a broad white band across the primaries. Whip-poor-wills are separated from other nightjars by their paler, less reddish color. They are distinguished from other nighthawks by the lack of a white wing-stripe and smaller wings with white or buff tips on outer tail feathers. (Cink, 2002)

Subspecies such as C. v. arizonae are larger, have longer tail feathers with more white on males, and darker tail tips on females. Caprimulgus vociferus oaxacae individuals are darker than the arizonae group with black spots on their crown and spotted breast. Caprimulgus vociferus chiapensis individuals are much darker and redder on top and bottom. Caprimulgus vociferus vermincularis individuals are paler, more reddish, smaller, and have fewer black spots on the scapulars. (Cink, 2002; Cink, 2002; Cink, 2002; Cink, 2002)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    43 to 63.7 g
    1.52 to 2.24 oz
  • Range length
    22 to 26 cm
    8.66 to 10.24 in
  • Average length
    25 cm
    9.84 in

Reproduction

Caprimulgus vociferus is thought to be monogamous. There is little known about whip-poor-will courtship displays. Females may try to solicit the attention of males by strutting on the ground with a lowered head and outspread wings and tail. Females circle in different directions while producing a guttural chuckle. The male will respond by approaching the female and undulating his body up and down. The male may circle the female and she then undulates her body up and down and quivers her wings. 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. (Cink, 2002; Ehrlich, et al., 1988)

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 the age of reproductive maturity for whip-poor-wills but it is assumed that it one year of age, which is the average for the nighthawk and nightjar family. Whip-poor-will reproductive cycles are synchronized with lunar cycles to result in better moonlit nights when foraging to feed their young. ("Nighthawks and Nightjars", 2001; Cink, 2002; Ehrlich, et al., 1988)

  • Breeding interval
    Whip-poor-wills breed twice per year.
  • Breeding season
    Whip-poor-wills breed from May through June.
  • Average eggs per season
    4
  • Average eggs per season
    2
    AnAge
  • Range time to hatching
    17 to 20 days
  • Average time to hatching
    19 days
  • Range fledging age
    14 to 20 days
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Both male and female whip-poor-will adults incubate the eggs, starting with the laying of the first egg. Both sexes trade incubation duties from dusk until dawn. 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-wills are semi-precocial birds and have the ability to avoid predators without parental care. (Cink, 2002)

  • Parental Investment
  • precocial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifespan/Longevity

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 for territorial space and for food that might impact their longevity. (Cink, 2002)

Behavior

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)

Caprimulgus vociferus is a medium-distance complete migrant. 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.

  • Range territory size
    18000 to 111000 m^2
  • Average territory size
    51000 m^2

Home Range

Little is known about the home range but some have been known to have territory sizes up to 111,000 square meters. (Cink, 2002)

Communication and Perception

Caprimulgus vociferus is known for its three tone call, sounding like "whip-poor-will", for which it is named. The primary whip-poor-will call is usually given by males to establish territories. The "quirt" is a soft call that increases as the individual becomes more and more excited. It is usually used by wintering, territorial birds. A "growl" is a fluttering sound used when two territorial individuals aggressively meet. The "hiss" is a repeated loud call given in response to predators. The "cur" is a guttural chuckle, often given during courtship, or for nest exchanges and when moving to new sites. (Cink, 2002)

Food Habits

Whip-poor-wills use aerial foraging techniques to catch their prey and primarily feed on night flying insects. They also feed on some non-flying insects. Known diets consist of moths, mosquitoes, flying beetles, ants, grasshoppers, and crickets. They especially prey on moths. (Cink, 2002; Ehrlich, et al., 1988)

  • Animal Foods
  • insects

Predation

Most losses through predation are 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 several meters away from the nest 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 cryptically colored and nocturnal, protecting them from some predation. (Cink, 2002)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Whip-poor-wills help to control populations of insects that they prey on. They also compete with other nightjars and nighthawks for habitat and food resources. (Cink, 2002)

Economic Importance for Humans: Positive

Caprimulgus vociferus is an insect eater, usually living near open, agricultural areas. It is likely that they help control insect populations that affect humans. Because whip-poor-wills are cryptic, nocturnal creatures they have no other known interactions with humans.

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There are no known adverse effects of whip-poor-wills on humans.

Conservation Status

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)

Other Comments

The species name, vociferus, is Latin for "voice-carrying" or "noisy." ("Goatsuckers Whip-poor-will, Caprimulgus vociferus", 2000)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Robert Duszynski (author), Kalamazoo College, Ann Fraser (editor, instructor), Kalamazoo College.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

References

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.

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