Rollers: Coraciidae

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ROLLERS: Coraciidae

DOLLARBIRD (Eurystomus orientalis): SPECIES ACCOUNTS


Rollers include three subfamilies: true rollers, ground-rollers, and the cuckoo roller. The three groups are medium-sized, brightly colored, and fairly large, stocky birds with a short necks; broad, strong syndactylous (sin-DACK-tuh-lus) feet, merged toes with no web in between; rounded wings; and short tails, though some species have tail streamers, a longer, central tail part. Sexes are similar or identical in color, depending on species. Rollers are 9 to 20 inches (22 to 50 centimeters) long, and weigh between 2.8 and 8.8 ounces (80 and 250 grams).

True rollers have plumage, feathers, of blue, blue-green, green, brown, or lilac, with olive, chestnut, or pink markings. Bills may be strong, arched, and hook-tipped, suited for grasping ground prey; or may be short and wide, suitable for catching flying insects. True rollers' wings are long and rounded, with tails that may be squared, slightly rounded, or somewhat forked, sometimes with longer outermost feathers.

Ground-rollers are more brown, buff or black in the plumage. They have rufous (reddish) or dark-green upperparts, simply patterned underparts, and bold facial patterns. Ground-rollers have large heads, strong bills, heavy bodies, short, rounded wings, long legs, and pointed tails.

Male cuckoo rollers are velvety gray; with a dark shiny green back, tail and wings; and a black eye stripe. Females and young birds are brown, with darker streaks.


Rollers range within Africa, southern Europe, and southern Asia to northeastern and southeastern Asia, and Australasia, east to the Solomon Islands.


Rollers live in forests, woodlands, savannas (flat grasslands), and within urban areas, preferring the tropics and subtropics.


Rollers eat a variety of foods such as insects, spiders, lizards, small mammals, and small birds. True rollers perch to wait for prey like arthropods, invertebrate animals with joined limbs, found around leaf litter or flying through the air. Ground-rollers eat mostly food found on the ground, capturing small vertebrates, animals with backbones, such as frogs and lizards hidden in the leaf litter or probing for prey with their bills into soft soils. Cuckoo rollers eat large insects and small reptiles that they find among trees and shrubs.


Rollers perch evenly spaced within groups. True rollers gather into migrating flocks, and are territorial most of the year. They are usually seen singly or in pairs, sometimes in post-breeding families. When breeding, they are noisy with loud cackling calls that occur during daring maneuvers. During non-breeding seasons, the birds are quiet and slow. Ground-rollers are territorial, especially when feeding. When in danger, they sit quietly in a well-concealed position. They make brief, gruff-sounding calls mostly during breeding.

During courtship, true rollers use loud sounds while rolling during through the air. Bowing is performed between male and female pairs while perched and facing each other, with mating occurring afterwards. Unlined nests are usually located within tree holes, but also found in crevices (narrow cracks in rocks), rocky parts of mountains, and buildings. Clutches, groups of eggs hatched together, are three to six unmarked white eggs, with an incubation period, time needed to sit on eggs, of eighteen to twenty days. Females do the sitting, but males help out. Newly hatched chicks are naked and helpless, with small feathers first appearing around seven days. Full feathers occur between seventeen and twenty-two days. Both parents feed nestlings, young birds unable to leave nest, for around thirty days, and for up to twenty days after fledging, learning to fly.

Ground-rollers breed during summers. Pairs defend their nesting territories, and courtship feeding of females by males is common. Nests are made in tree hollows, but some nest in chambers at the end of a burrow excavated, dug, by the birds. Two to four white eggs are laid. Incubation appears to be performed by the female, and both parents feed nestlings.


People generally have little interest in rollers. Some exceptions occur; for instance, body parts of rollers are used in love potions, drinks supposedly used to increase sexual desire. Rollers have also been viewed as good omens. People hunt ground-rollers for food because they are easy targets.


True rollers are common throughout all or part of their ranges, with one species considered Vulnerable, facing a high risk of extinction in the wild. Ground-rollers have four species that are considered Vulnerable due to deforestation. Cuckoo rollers are generally common and survive in small, fragmented forest patches. However, they are being adversely affected by widespread land clearing.


Physical characteristics: European rollers are heavily built, large rollers with no tail streamers. Their head, neck, and underparts are bright pale blue, with rufous to chestnut upperparts, blue square-tipped tail, and vivid blue wing patch. The throat and breast are streaked with white. They have a short black streak through the eye, and a brownish black bill with a white base. The two central tail feathers are dark olive-gray, with the remaining feathers greenish blue with darker bases. They are 12.2 to 12.5 inches (31 to 32 centimeters) long and weigh between 3.9 and 6.7 ounces (110 and 190 grams). Females and males look alike.

Geographic range: They breed throughout Europe, western and southwestern Asia, and the Middle East; and, while not breeding, live in the eastern half of Africa, and along the northern and central coasts of western Africa, and as far south as South Africa.

Habitat: They exist in open woodlands, wooded grasslands, cultivated fields, oak forests, pinewoods, river valleys, urban parks, and gardens of lowlands. They range from sea level up to about 2,000 feet (600 meters). They do not like open water; steppes, treeless, grass-covered plains; and plains, dry land with few trees. During breeding season, they are attracted to sunny lowlands.

Diet: European rollers eat mostly insects such as beetles, grasshoppers, locusts, crickets, cicadas (suh-KAY-duhz), mantids, wasps, bees, ants, termites, flies, butterflies, and caterpillars. Occasionally, they eat scorpions, centipedes, spiders, worms, frogs, lizards, snakes, and birds. While on their perches, European rollers watch for ground prey. Seeing food, they expose long, broad wings as they attack. They then return to the perch. Before eating prey, they repeatedly strike the food against the perch. They also catch insects in midair. Undigested remains are regurgitated (re-GER-jih-tate-ud; brought up from the stomach) in pellets.

Behavior and reproduction: European rollers are often seen hunched on a lookout perch on a tree, post, or telephone wire. They migrate seasonally to Africa, mainly in the east and south. They are noisy birds, often calling out a short gruff "rack," a chattering "rack rack rackrak ak," or a screeching "aaaarrr" (which is a sound of warning). They are noticeable while in their breeding territories. During wintering periods, they are quiet and slow moving birds. They breed in pairs, but loose flocks migrate together. They are active on warm days, but less active during rainy ones.

They form monogamous (muh-NAH-guh-mus) pairs, having only one mate, and they strongly defend their nests. Their courtship displays involve deep ascents followed by spectacular twisting dives that show off their wing colors. Croaking and rattling calls (like "ra-ra-ra-raa-raa-aaaaaa-aaaar") accompany the display. They breed from May to June, with females laying two to six (usually four) eggs in an unlined, usually pine or oak, tree hollow, crevice in rock faces, or hole in walls of buildings. The incubation period is between seventeen and nineteen days, performed totally by the females. Both parents feed chicks. The fledgling period, time while the young grow their flying feathers, is twenty-five to thirty days.

European rollers and people: People admire European rollers for their beauty and like them because they eat insects, pests to humans. However, they are still often hunted for food, sport, and taxidermy, the stuffing and mounting of animals in a lifelike state.

Conservation status: European rollers are not threatened—they still number in the millions—however their numbers continue to decrease in Europe. ∎

DOLLARBIRD (Eurystomus orientalis): SPECIES ACCOUNTS

Physical characteristics: Dollarbirds are stocky, dark greenish-blue or purplish birds with a large head; short, thick neck; short legs; short-looking, square-ended tail; and short but broad, heavy red bill. They have broad and long wings with central tail feathers that are blackish with dark blue bases and outer feathers that are blackish with purple-blue edges and greenish-blue bases. Dollarbirds have white-silvery or pale blue "dollar"-like circles on their open wings, which is noticeable while flying. The forehead and chin are blackish brown; back of the neck and ears are very dark olive-brown; and back and rump are bluish olive. The throat is purple with narrow blue streaks; while the breast, sides, belly, undertail, and underwing areas are green-blue. Their eyes are dark brown, while legs and feet are bright red. They are 9.8 to 11.0 inches (25 to 28 centimeters) long, and weigh between 4.0 and 5.6 ounces (115 and 160 grams).

Geographic range: Dollarbirds are located from southeastern Asia to the Philippines, Indonesia and the northern and eastern coastal lands of Australia.

Habitat: Dollarbirds reside in deciduous woodlands, evergreen forests, forest margins, savannas, farmlands (such as rubber and coffee plantations), urban parks, and gardens, up to elevations of 4,900 feet (1,500 meters). They favor hot lowlands and foothills.

Diet: They eat large insects that are captured in flight, especially beetles, crickets, mantids, grasshoppers, cicadas (suh-KAY-duhz), shield-bugs, moths, and termites. Dollarbirds occasionally take insects from the ground. Once crushed by their bills, they are swallowed. They feed mostly in the late afternoon and evening.

Behavior and reproduction: Dollarbirds live alone or in pairs. For much of the day they sit inactively on a perch. They often wag their tail up and down when about to fly, but otherwise sit quietly, moving only the head. The birds migrate to higher latitudes from their normal residences in the tropics. They are rather silent, but occasionally are noisy, uttering a hoarse, raspy "chak," or a series of "krak-kak-kak" or "kek-ek-ek-ek-ek-k-k-k". Dollarbirds are noticeable with their high, rotating flights or when perched on top of high trees. They fly in large flocks when migrating or when feeding on swarms of flying insects.

They are monogamous birds that breed in the summer. The breeding pair will defend their nesting territory. Dollarbirds use loud calling and aerobatics, spectacular flying stunts, in courtship rituals. Females lay three or four eggs, which are laid in high tree hollows, sometimes in woodpecker holes. Nests are often used several years in a row. The incubation period is twenty-two to twenty-three days. Both parents feed the chicks. Parents and chicks leave for wintering areas when chicks are able to fly.

Dollarbirds and people: Dollarbirds have no known significance to humans.

Conservation status: Dollarbirds are not threatened. ∎



del Hoyo, Josep, Andrew Elliott, Jordi Sargatal, Jose Cabot, et al., eds. Handbook of the Birds of the World. Barcelona: Lynx Edicions, 1992.

Dickinson, Edward C., ed. The Howard and Moore Complete Checklist of the Birds of the World, 3rd ed. Princeton, NJ and Oxford, U.K.: Princeton University Press, 2003.

Forshaw, Joseph, ed. Encyclopedia of Birds, 2nd ed. San Diego, CA: Academic Press, 1998.

Fry, C. Hilary, and Kathie Fry. Kingfishers, Bee-Eaters and Rollers: A Handbook. Princeton, NJ: Princeton University Press, 1992.

Harrison, Colin James Oliver. Birds of the World. London, U.K. and New York: Dorling Kindersley, 1993.

Perrins, Christopher M., and Alex L. A. Middleton, eds. The Encyclopedia of Birds. New York: Facts on File, 1985.

Stattersfield, Allison J., and David R. Capper, eds. Threatened Birds of the World: The Official Source for Birds on the IUCN Red List. Cambridge, U.K.: BirdLife International, 2000.