Pigeons, Doves, and Dodos: Columbiformes
PIGEONS, DOVES, AND DODOS: Columbiformes
Species of the order Columbiformes include the pigeons and doves, which are compact birds with broad, rounded, powerful wings; short bills; short legs; and short necks. They range in size from the tiny 1.1-ounce (30-gram) Australian diamond dove to the large Victoria-crowned pigeon, which can weigh as much as 6.6 pounds (3 kilograms). Males tend to be slightly larger than females in size. In most species, males and females are similarly colored, although there are a few tropical species where males are much more colorful than females. Many pigeon and dove species are gray, brown, or cream in color. However, some tropical species may be green, red, purple, pink, blue, or orange. One particularly colorful species is the golden dove of Fiji, which can be brilliant orange or a metallic green and gold.
The extinct dodos were large, flightless species weighing as much as 62 pounds (28 kilograms). They had large bellies; short, strong legs; and large bills. They had tiny wings and short tails. They were probably blue or brownish gray in color.
Pigeons and doves are found worldwide, except in the Arctic and Antarctic regions and at high elevations. Particularly large numbers of species are found in tropical areas, especially those near the Indian Ocean and Pacific Ocean. About 60 percent of pigeons and doves are found on small islands far from continental land masses. Dodos were previously found on several small islands in the Indian Ocean.
Pigeons and doves occupy many habitat types, although most species live in forests. Most pigeons and doves are arboreal, they live in trees. A few tropical pigeons and doves are terrestrial, ground-dwelling, and some occupy cliff faces. Dodos inhabited forests as well.
Most species of pigeons and doves eat primarily seeds, fruits, and leaves. Some also eat invertebrates, animals without backbones, such as insects, though they generally do not form a large part of the diet. One exception is the atoll fruit-dove, which eats large numbers of insects as well as small vertebrates, animals with backbones, such as lizards. Pigeons are also able to drink water by sucking it up directly. Dodos ate fruit, seeds, and other vegetable matter.
BEHAVIOR AND REPRODUCTION
Some pigeons and doves are solitary, with individuals living alone. The majority of species, however, form small or large flocks, and many even breed together in large colonies. Pigeons and doves often gather near food sources. For example, as many as 100,000 wood pigeons have been observed in a grain field in Germany. During the breeding season, the South American eared dove regularly gathers in flocks of as many as five million individuals. The North America passenger pigeon, which is now extinct, may once have been the most abundant bird on earth. Flocks of passenger pigeons could include as many as billions of individuals.
Most pigeons and doves make noises that sound like "coos" and "oohs." Other species can make whistles, grunts, or clicks. A number of species are almost completely silent.
Birds of the order Columbiformes have an unusual strategy for escaping predators. Their feathers are only loosely attached to the skin and fall out very easily. When a predator grabs a pigeon or dove, a large number of feathers are shed at once, leaving the predator with a mouthful of feathers while the bird quickly escapes.
Courtship in pigeons and doves involves bowing, stretching, and flying. Pigeons and doves are monogamous, a single male mates with a single female during the breeding season. However, the same mate is not necessarily kept from one breeding season to the next. Arboreal species build a simple nest of twigs, while terrestrial species scrape a small depression on the ground. The female lays one or two eggs at a time in most species, although some species may lay as many as four. Species that breed in large colonies, or large pigeons and doves in rainforest habitats, tend to produce only one egg during the breeding season. The eggs are usually white in color, though some species have cream or brownish eggs. Pigeon chicks, which are sometimes called "squabs," are helpless at birth, and have only a few feathers. Both parents help feed and take care of the young. Pigeons and doves are unique among birds in that adults produce a cheesy secretion in their crops known as "crop milk" which they feed to their young. This means that even when food is scarce, parents are able to feed the young. Chicks grow very quickly, and are able to leave the nest between seven and twenty-eight days after hatching. Some leave the nest before their wing feathers are fully grown. Chicks tend to have brown feathers, and only gradually take on the adult coloration.
PIGEONS, DOVES, DODOS, AND PEOPLE
Pigeons have long been raised and bred by human beings for food or as pets. Some species have also been trained to transport written messages. Dodos were hunted for food and sport until they became extinct. The passenger pigeon also went extinct due to human hunting.
About one-third of the 316 existing pigeons and doves are believed to be threatened. Many of these species occupy small islands and have very small ranges. Some species have already been driven to extinction by human activity, including the passenger pigeon and the dodo.
Pigeons and doves are unique among birds in that adults produce a special "crop milk" to feed their young. Crop milk is named after the crop, a pouch-like organ in the adult throat where the milk is produced. Crop milk is a soft, nutritious, cheesy substance. Because of crop milk, pigeon and dove parents are able to feed their young even when there is little food available, as long as they themselves are fat and healthy. Crop milk is produced by both parents.
FOR MORE INFORMATION
del Hoyo, J., A. Elliott, and J. Sargatal, eds. Handbook of the Birds of the World. Vol. 4, Sandgrouse to Cuckoos. Barcelona: Lynx Edicions, 1997.
Perrins, Christopher, ed. Firefly Encyclopedia of Birds. Buffalo, NY: Firefly Books, 2003.
"Columbidae (Pigeons and Doves)." The Internet Bird Collection. http://www.hbw.com/ibc/phtml/familia.phtml?idFamilia=71 (accessed on June 12, 2004).
"Order Columbiformes (Doves and Pigeons)." The University of Michigan Museum of Zoology Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/classification/Columbiformes.html#Columbiformes (accessed on June 12, 2004).