Lifestyle and Lifespan
The 11 species of roller occur in Africa, Asia, and Europe. They are mostly insectivores and will catch insects in the air while flying. Rollers are usually brown and blue. They will nest in old tree cavities and lay 2 to 4 eggs.
Head and upper mantle are white while the back is greenish black. The rest of the body is dark blue and the tail feathers are light blue. The outer tail feathers are 6 cm long and called tail streamers.
They have a strong body and a crow-like beak widened at the base. They have short legs and weak feet and rarely walk or hop. The three anterior toes are joined along their basal segments. They are good flyers with long wings. The tail streamer on an adult is 6 cm long.They have very keen eyesight and are among the first birds to come to a grassfire, termite hatch or locust swarm.
A savanna species often found in forest and woodlands.
Blue-bellied rollers make some seasonal movements but no great migration. They will travel great distances to fires to feast on fleeing insects.
Blue-bellied rollers mostly eat insects but will also eat small reptiles and oil palm fruit.
As an insectivore and being well-adapted to human areas, blue-bellied rollers help humans by keeping down insect pest populations. This trait also helps other animals who are also beleaguered by pest insects.
They are conspicuous and usually noisy birds. They frequent the topmost branches of tall trees from which they indulge in wild erratic flights, accompanied by loud cries and attack any large bird that passes. Others perch on dead branches on low trees from which they swoop down on their prey.
Groups of blue-bellied rollers are usually from 3 to 7 individuals, though they can be larger. They play, vocalize, and hunt together. They will also attack other animals together to defend their territory.
Blue-bellied rollers are usually seen in pairs, though there is evidence that males will court and mate with multiple females. They nest in holes in trees and lay two or three white eggs. Incubation lasts about three weeks and the young are fledged in about four weeks. Courtship involves fast chases on the wing with the following bird breaking away and rocketing earthwards, rolling from side to side and calling raucously all the while. They are territorial and reversed copulations have been witnessed which seem to be dominance displays.
Blue-bellied rollers usually lay 2 to 3 eggs in one clutch. The male and female roller will incubate the eggs though it is unclear how much time the male spends in this role. After four weeks, the offspring fledge and will leave their parents' care.
Because of the large range of blue-bellied rollers, it is difficult to get an accurate count. Populations are decreasing but not at a high rate, leading to their listing as Least Concern by the IUCN. Their woodland habitats are being developed and causing a problem for certain populations. They have adapted to live near humans where there is cleared ground.
Oakland Zoo has blue-bellied rollers on exhibit to educate the public about this bird. They are often a focus of feeding talks because of their amazing in-flight feeding.
You can help blue-bellied rollers by educating your friends and family about habitat loss as a conservation issue.
Blue-bellied rollers will dive straight down towards their prey from 30 feet in the air. They will also frequent grass fires to catch the fleeing insects.
Fry, C. Hilary and Kathie Fry. 1992. Kingfishers, Bee-eaters and Rollers: A Handbook. Princeton University Press.
Mackworth-Praed, C.W. and C.H.B. Grant. 1957. Birds of Eastern and North Eastern Africa. Vol, 1. London. Longmans Green & Co.
Moynihan, M. 1990. "Social, sexual and pseudosexual behavior of the Blue-bellied Roller, Coracias cynogaster: the consequences of crowding or concentration" Smithsonian Contributions to Zoology, 491:1-23.
BirdLife International. 2016. Coracias cyanogaster. The IUCN Red List of Threatened Species 2016: e.T22682908A92967763.
http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22682908A92967763.en. Downloaded on 20 September 2017.
"Blue-bellied Rollers, Coracias cyanogaster." beautyofbirds.com, 20 Sept. 2017, https://www.beautyofbirds.com/bluebelliedrollers.html.
"Blue-bellied Roller." The Maryland Zoo in Baltimore, 20 Sept. 2017, http://www.marylandzoo.org/animals-conservation/birds/blue-bellied-roller/.