Dainty aerial acrobats

As many as 1,000 mud pellets make up one single nest.

As many as 1,000 mud pellets make up one single nest.

With the second edition of the International Conference on Indian Ornithology (ICIO-2013) around the corner (November 19-23), many knowledge gaps in the world of Indian birds are likely to get filled.

Organised by Salim Ali Centre for Ornithology and Natural History in Coimbatore, the conference will be attended by 50 scientists from about 10 countries.

In this context, the tale of the docile, dainty and diminutive wire-tailed swallows about which ornithologists till date have limited knowledge needs to be highlighted.

Known to be great airborne acrobatic artists with seemingly reckless flying frolics, the mission of the humble swallow is to devour nearly a thousand tiny insects every day to keep its supple body energised.

These black-and-white birds are often found in the countryside, particularly near water bodies and rural human habitation. Being fast flyers, they feed on flying insects, especially houseflies, mosquitoes, gnats, midges, etc. With incredible manoeuvrability and precision, they are natural hunters of airborne insects and help in reducing the numbers of malaria and dengue-causing mosquitoes.

Belonging to the swallow bird family, all species of swallows are somewhat similar in habits and appearances to other aerial insectivorous cousins, such as the closely related martins and the unrelated swifts. From a distance, all the 30-odd species of swallows, martins and swifts that are found in the Indian sub-continent look alike to a casual birdwatcher or even an experienced ornithologist. Only with the aid of powerful binoculars or extra-long lenses one can distinguish the subtle differences among them.

Recently Swiss scientists were amazed to discover that Alpine swifts can fly non-stop for 200 days while migrating. After attaching lightweight electronic monitors to half a dozen Alpine swifts, researchers say that the birds remained airborne for more than six months, eating, drinking and sleeping in air. Since the 1970s, ornithologists have speculated that the Alpine swift's smaller cousin, the common swift, stayed airborne for much of the year, although that concept is based on speculation.

Researchers at the Swiss Ornithological Institute carefully captured six Alpine swifts prior to their epic migration. Each of the birds was harnessed with wafer-thin electronic monitors that were smaller than postage stamps. The devices were designed to use sunlight to track the bird's location, and also measured their position and movement. When the birds returned to Switzerland seven months later from their African sojourn, three of them were recaptured and their data downloaded.

What the researchers found was that during the daytime, the birds did not stop for rest. Even at night, they seemed to be gliding for long distances instead of flapping their wings which clearly indicates that they were saving energy for the long-distance travel. But how did they eat and drink is a mystery and it can be only be speculated that the swifts feed on so-called aerial plankton, insects that float and fly in the sky. More such advanced research is underway to decipher details of these tiny marvels of nature.

Meanwhile, the wire-tailed swallows that are found both in the Asian and African continents have an extremely large range and their population trend appears to increasing even though the population size has not been quantified in scientific terms. This is the only species in the family of swallows to have fine wire-like long filaments in the outermost tail feathers; hence the name. While both male and female swallows have almost similar appearance, the female has shorter ‘wires’ and the juveniles lack ‘wires’ in the tail. While the Asian form is larger and longer-tailed than the more abundant African wire-tailed swallow.

Wire-tailed swallows are mostly resident except for some populations in northern India that migrate down south during winters. They are usually seen in pairs close to water bodies. Their short wide bills help them feed as they sweep through clouds of swarming insects near water, grasslands and above the forest canopy.

Swallows were originally cave breeders but as many hills and rocky formations vanishing with burgeoning development activities, they now construct neat half-bowl nests of mud under man-made structures such as tall buildings, bridges, eaves, etc. As the birds pick up mud and carry it in their mouths, they form it into small pellets. If one looks closely at a swallow nest, many individual mud pellets, as many as 1,000, can be seen that makes up one single nest (see picture). The open cup on top of the mass of mud is lined with feathers, cloth threads and other soft items. It might take the parents a full week to construct the nest, and they constantly repair it.

Unlike many other swallow species, which nest in colonies, the wire-tailed swallows are solitary and territorial nesters. Scientists have reported that females constantly judge their mates by their looks, in particular by the reddish colour of the males’ breast and belly feathers. Perhaps the intensity of the reddish colour is an indicator of the male’s health, status, and ability to raise the young. Another study revealed that females prefer to mate with males that have the longest and most symmetrical tails.

Dr. Rajah Jayapal, coordinator of ICIO-2013, says: “Though Indian ornithology today is an established field of research, it lacked a common platform in the past to bring together bird biologists and conservationists to review the progress of ornithological research in the country. The conference will summarise the current progress of Indian ornithological research and deliberate on gaps in our knowledge and future directions.”

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Printable version | May 20, 2022 10:17:15 pm |