Feathered engineering

Polygamist: Feathers of male bayas turn yellow during the breeding season. Photos: N. Shiva Kumar  


It is monsoon again and bayas or weaver birds are back to their frolicking mood — mating, building artistic nests and bringing up families

In recent months, the house sparrow has hogged all the limelight and even nominated as the Delhi State Bird. On the other hand, a similar lookalike sparrow survives in obscurity and is relegated to the wilderness. In fact, it disappears into thin air for most part of the year and appears on the horizon like a pop-up on a computer screen only in the rainy season.

The dull brown weaver bird, commonly known as baya, has inconspicuous hues in the off-season. However, when the monsoon begins and the parched earth turns emerald they dramatically arrive on the scene. This small bird gets into the ‘breed and brood’ mood and their subdued brown feathers turn brilliant yellow with contrasting dark chocolate. Only the male turns attractive though, donning a yellow crown and chest for the love season, while the female retains its original colour.

The baya weaver’s nest is an architectural achievement which dangles from tree branches. The nest looks like a long pipe with a bulge in the middle with an entrance pointing downward. The bulbous structure is the nesting area with a long entry tube which makes it difficult for snakes and lizards to attack. Although the latticed nest looks delicate and precarious, they are sturdy and fastened taut to a twig — so much so they are impossible to be dislodged even by high winds, storms and cloudburst. Most nests endure through the four-month breeding season and sometimes even up to a year. After the breeding season, smaller birds and rodents take advantage of the readymade abodes and roost in the abandoned nests. The hardy nests are made entirely out of strips of grass or thin ribbons of palm leaves which the birds assemble by cutting a notch in blade of long grass, then stripping off a 30 to 60cm length. The strands are woven into cosy one-bedroom apartments for the mom and children to thrive.

As a passionate birdwatcher, I was fortunate to observe and photograph a large colony of 70 baya nests some years ago in the heart of Noida when natural trees and open spaces existed (see picture). Today’s young generation living in cities rarely gets such opportunities because bayas no more nest in urban areas. Even if they do, they have to put up with unruly situations as the one I noticed in Sector 14 in Faridabad. They have hazardously chosen a lonesome palm tree in the parking area of a shopping centre and made 20 nests despite a lot of commotion.

Strangely, the male and female bayas have their works distinctly demarcated. While the male has the onus of building the intricate nests, the female brings up a hungry brood of chicks. The male baya, being a polygamist, is capable of acquiring many partners; he painstakingly weaves a splendid nest that is half-finished and invites a lover to inspect the construction. If the female is dissatisfied, the male has to engineer another improved version. Once the female is satisfied, they make love and the male goes scot-free to find another lover and repeat the laborious nest-building activity. The male is capable of playing husband and father to four or five families all at once. More nests mean more wives but it is not an easy venture as scientists have found out that a single completed nest comprises an incredible 3,437 grass strips.

According to Dr. R. Nagarajan at the Department of Wildlife Biology at AVC College in Tamil Nadu, Bayas are ingenious and construct nests above natural water surface like lake, pond and even inside abandoned wells. In desperate situations, they even use telephone lines and electric power line wires in the middle of sugarcane fields or streams to hang their nests. They only choose safe spots which are not easily accessible to predators, including man. Incredibly, the baya has the stamina to make a minimum of 500 trips to complete one nest in about 18 days.

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Printable version | Dec 19, 2017 1:23:03 AM | http://www.thehindu.com/sci-tech/energy-and-environment/feathered-engineering/article3874666.ece