The true, or forest orioles include 29 to 30 species of medium-sized birds that make up the family Oriolidae. These birds occur in Africa, Europe, Asia, Southeast Asia, the Philippines, New Guinea, and Australia. Their usual habitats are forests, open woodlands, and savannas. Most species are tropical, but some migratory species occur in temperate regions.
Orioles are jay-sized birds with long, pointed wings, and a strong, pointed, slightly down-curved bill, which may be colored red, blue, or black. Male orioles are brightly colored birds, commonly yellow with black patterns on the wing, tail, and head. Females have a more subdued coloration. The family name, Oriolidae, is derived from the Latin word aureus, meaning golden, and refers to the bright-yellow base color of the golden oriole of southern Europe.
Orioles tend to skulk in dense cover in wooded areas, and are not easily seen. They have a melodious, if somewhat quiet song, and louder, harsher, call notes. Courting includes spectacular, closely coordinated pursuits of the female by the male through the tree canopy. The pendulous, tightly woven, cup-shaped nest of orioles is constructed by the female in a forked branch of a tree, and contains two to five eggs. The female does most or all of the incubation, but is fed by the male during her confinement. Both parents rear the young. The figbirds (Sphecotheres spp.) of Australasia construct much looser nests of twigs.
Orioles mostly feed on invertebrates in the tree canopy. Unlike most other birds, orioles will feed on hairy caterpillars, which can sometimes be quite abundant. However, these insect larvae are rubbed and beaten by orioles against a branch, to remove many of the hairs before the prey is eaten. Orioles also eat small fruits when they are available.
The golden oriole (Oriolus oriolus ) is a relatively abundant and well-known species of forests and wooded parks and gardens of temperate Europe and western Asia. This species winters in Africa, Madagascar, India, and Sri Lanka. The attractive male has bright-yellow plumage, with a black tail and upper wings, and a black mask. The female is a lime green color. The golden oriole is bold and pugnacious in the vicinity of its arboreal nest, attacking and driving off potential predators such as crows and small hawks.
The black-headed oriole (Oriolus xanthornis ) is another relatively common and widespread species, occurring in forests in south and Southeast Asia. The black-naped oriole occurs from India to southern China and Southeast Asia, as far as the Philippines. The yellow oriole (O. flavocinctus ) and olive-backed oriole (O. sagittatus ) are greenish yellow Australian species. The black-and-crimson oriole (O. cruentus ) of Malaya, Borneo, Sumatra, and Bali is mostly black-colored, with dark, crimson patches on the breast and on the wings.
The yellow figbird, or bananabird (Sphecotheres viridis ), occurs in various types of forests in northern Australia. This greenish and yellow species commonly nests in the immediate vicinity of a nest of the drongo (Chilbea bracteata ) or helmeted friar bird (Philemon yorki ), both of which are aggressive species that drive away predators, but do not bother other songbirds.
The Asian fairy-bluebird or blue-backed fairy bluebird (Irena puella ) occurs in lowland rainforests from India to Borneo and Sumatra in southeast Asia. The male fairy-bluebird is a very attractive bird, with a bright blue back, and a black face and breast. The female is a more uniformly and subtly colored blue. This species is placed by some avian taxonomists in the family Irenidae, which also contains the leafbirds.
Some species of medium-sized birds of the Americas are also commonly known as orioles. However, these orioles are various species of mediumsized birds in the blackbird family (Icteridae), which also includes blackbirds, grackles, cowbirds, meadow-larks, and the bobolink. For example, the northern oriole (Icterus galbula ; the eastern race is known as the Baltimore oriole) is a common songbird of open forests in North America, where it builds its characteristic, pendulous nests, often in elm trees.
Forshaw, Joseph. Encyclopedia of Birds. 2nd ed. New York: Academic Press, 1998.