roller, common name for brightly colored Old World birds noted for performing somersaults in flight. They include the rollers proper (subfamily Coraciinae ) and ground rollers (subfamily Brachypteraciinae ) of the family Coraciidae, as well as the monotypic cuckoo roller ( Leptostomus discolor ) of another family, Leptostomatidae. The rollers comprise approximately a dozen species of solitary, jaylike birds, widespread throughout the tropical and temperate areas of the Old World. They are stout-bodied and large-headed birds, ranging from 91/2 to 13 in. (24–33 cm) long, with long, straight beaks that end in hooked tips. Their colors run to greens, blues, and reddish or yellowish browns, with little distinction between sexes. Rollers are strong flyers and feed while on the wing, usually on insects and small birds but occasionally on fruit. They lay their three to six white eggs in tree or rock holes, to which they add bits of grass, straw, or feathers. The slightly smaller tropical broad-billed rollers (genus Eurystomas ) do not actually tumble or roll in flight. The five species of ground rollers are confined to the island of Madagascar. They differ from the true rollers in being ground feeders and thus show the expected adaptations of this way of life: longer and stouter legs; shorter, more rounded wings; and less bright but more cryptic coloration. Four species inhabit the forest floor, and one, the 18-in.-long (46-cm) Uratelornis chimaera, dwells in arid scrub. Ground rollers feed on insects and small animals and build their hole nests in the ground. The cuckoo roller is also found on Madagascar, as well as on the nearby islands of Comoros and Mayotte. It is about 17 in. (43 cm) in length and somewhat resembles the cuckoo in its coloration and its crested head. It differs from all other rollers in the possession of an outer toe capable of being turned backwards and a bill overhung with large tufts of feathers. A creature of forest and brushland, it feeds on large insects and lizards and lays its eggs in a tree-hole nest. Rollers are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Coraciiformes, families Coraciidae and Leptostomatidae.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.