The order Caprimulgiformes is known as nightjars and "nightjar" is also the name of the largest family in the order. An order consists of animals with similar characteristics. Caprimulgiformes have large heads, and their large eyes help them see at night. Also large is the gape, the width of the mouth when open. Around the mouths of some birds are whisker-like bristles. The birds have short legs, and many birds have one toe on each foot that points backward, forward, or away from the foot.
Caprimulgiformes have plain plumage. Adults' feathers are brown, gray, brownish yellow, and rufous, a reddish brown. Plumage is patterned, and this protective coloration helps Caprimulgiformes blend in with trees and hide from predators. Members of this order are also known as night birds because they are nocturnal, active at night.
The nightjar family, Caprimulgidae, consists of nineteen genera and seventy-seven species. Birds range in length from 6 to 16 inches (15 to 40 centimeters) and weigh from 0.7 to 6.6 ounces (20 to 188 grams). Members of this family have long wings and tails. They do not have bristles around their mouths. Furthermore, on the middle toe is a claw that is serrated, segments of the claw resemble the teeth of a comb.
The oilbird family, Steatornithidae, has one genus and one species. The birds have hooked bills and are about 17 to 19 inches (43 to 49 centimeters) long. They weigh from 13 to 16 ounces (375 to 455 grams). They are similar to nightjars, and have long wings and tails.
The frogmouth family, Podargidae, consists of two genera and thirteen species. The family name comes from the frogmouth's huge gape and the large beak, which resemble the mouth of a frog. Birds range in length from 7.5 to 24 inches (19 to 60 centimeters) and weigh from 1.5 to 23.6 ounces (43 to 670 grams). Wings and tails are rounded.
The owlet-nightjar family, Aegothelidae, is sometimes called the owlet-frogmouth family. The family consists of one genus and eight species. Owlet-nightjars range in length from 7 to 12 inches (18 to 30 centimeters) and weigh from 1 to 3.5 ounces (29 to 98 grams). Birds' eyes face forward, and the gapes are as wide as birds' heads. Owlet-nightjar wings and tails are long.
The potoo family, Nyctibiidae, consists of one genus and seven species. Birds range in length from 8 to 23 inches (21 to 57 centimeters) and weigh from 1.6 to 2.2 ounces (46 to 624 grams). Birds resemble frogmouths, but are thinner and have smaller bills. Wings and tails are long.
Nightjars, the largest family in the order Caprimulgiformes, are located throughout much of the world. There are twenty-five Caprimulgidae species in Africa, and nightjar species live in countries in North and South America, Europe, Asia, and Australia. These birds are not found in the Arctic and Antarctic.
Frogmouth species live in Asian countries including India, Vietnam, Java, and the Philippines. They also range in Australia and South Pacific countries including Tasmania, New Guinea, and the Solomon Islands.
Potoos live in Central and South America, and are found in countries from Mexico to Uruguay. They also range in Hispaniola and Jamaica.
Habitats are as varied as the families in this large order. Some members of the nightjar family live in rainforests, where heavy rainfall throughout the year produces abundant growth. They also range in grasslands and savannas, where there are fewer trees. Nightjars also live in semi-arid deserts and forests.
Oilbirds live in caves along coasts and in the mountains. They range in forests including coniferous or evergreen forests¸ where trees do not shed leaves. Frogmouths live in rainforests and other wooded areas. Owlet-nightjars live in tropical forests, savannas, open woodland, and scrub, areas with under-sized vegetation. Potoos live in tropical forests and in trees in savannas.
Oilbirds eat fruit that they pluck from trees. All other caprimulgiforms eat arthropods, animals with no backbones. These include insects, spiders, and millipedes. Larger birds eat vertebrates, creatures with backbones, like frogs, mice, small birds, and bats.
BEHAVIOR AND REPRODUCTION
Caprimulgiformes are nocturnal, meaning they are active at night. Some families are also crepuscular (kri-PUS-kyuh-lur), becoming active at twilight. Birds in this order communicate with calls.
Most species are monogamous (muh-NAH-guh-mus), mating with one partner. Nightjars do not build nests, and the female lays one to two eggs. She and the male incubate the eggs, sitting on them until they hatch. In some species, both parents feed the young birds. Female oilbirds have a clutch of two to four eggs, and both parents incubate them. Female frogmouths lay from one to three eggs, and both parents incubate. Owlet-nightjars lay three to four eggs. Females incubate and both parents feed the young. Potoos usually have a clutch of one egg. Both parents incubate and care for the young.
While frogmouths, owlet-nightjars, oilbirds, and potoos live their lives in one area, some nightjar species travel great distances. European nightjars breed in Europe and migrate to Africa for the winter.
CAPRIMULGIFORMES AND PEOPLE
In the Caprimulgiformes order, some family names reflect the relationship between birds and people. Nightjars have been called "goatsuckers" because people believed that the nocturnal birds flew down and sucked the milk from goats and cows. When animals died, people mistakenly blamed the birds. However, nightjars do not drink milk.
The name "nightjar" comes from Europe. The bird's loud call can last several minutes. Since birds are nocturnal, their noise "jarred" or startled sleeping people and woke them up.
Furthermore, oilbirds received their names because the birds eat fruit containing oil and fat. In the past, people captured the birds and boiled them to collect the oil. They used the oil for cooking or as fuel to light their lamps. Now people are interested in observing oilbirds. People visit caves where these unique birds roost during the day.
There is concern about the future of some Caprimulgiformes species, according to the World Conservation Union (IUCN). These species are threatened by loss of habitat as forests are cleared for farming and development.
The Puerto Rican nightjar is Critically Endangered, facing an extremely high risk of extinction in the wild in the immediate future. However, conservation efforts could result in the ranking being changed to Endangered, facing a very high risk of extinction in the near future.
The Itombwe nightjar and the white-winged nightjar are Endangered. Only one specimen of the Itombwe nightjar was found in the Democratic Republic of the Congo. White-winged nightjars live in Bolivia and Brazil. When this species was discovered in Paraguay, it was a sign that the population was larger. The species ranking was changed from Critically Endangered to Endangered.
Two Indonesian species, the satanic-eared nightjar and Bonaparte's nightjar, are Vulnerable, facing a high risk of extinction in the wild.
GUIDED BY ECHOES
Oilbirds move safely in dark caves by making clicking sounds. The birds listen to the echoes made when the sounds bounce off surfaces like cave walls. Oilbirds know to fly away from the echoes or they will crash into something. The guiding process oilbirds use is called echolocation. Bats, porpoises, and whales also use echolocation.
FOR MORE INFORMATION
Stuart, Chris and Tilde. Birds of Africa From Seabirds to Seed Eaters Cambridge, MA: The MIT Press, 1999.
Pratt, Thane K. "Evidence For A Previously Unrecognized Species of Owlet-Nightjar." The Auk (January 2000): 1–11.
"Australian Owlet-Nightjar." Australian Museum Online. http://www.amonline.net.au/factsheets/owlet_nightjar.htm (accessed on June 1, 2004).
"White-throated nightjar." Environmental Protection Agency/Queensland Parks and Wildlife Service. http://www.epa.qld.gov.au/nature_conservation/wildlife/nocturnal_animals/birds/whitethroated_nightjar/ (accessed on June 1, 2004).