Resident watch Environment

It is time to count baya weaver nests

A female baya weaver inspects a nest built by the male. And the male baya weaver looks on. Photo: Rama Neelamegam    

In the far-flung outskirts of Chennai and in neighbouring districts, some palmyra trees would now be sporting newly-sprung, intricately-woven, helmet-shaped nests, found in various stages of completion. Tall thorny shrubs teetering on the edge of waterbodies may also be bedecked with these accoutrements. They signal that male baya weavers are hard at work, making a spirited and indefatigable effort again to raise a family.

The baya weaver’s (ploceus philippinus) biological clock ticks to the monsoons, which is when it breeds and raises families. The male baya weaver can find it a drudgery to win over a female. To get the nod, he has to dazzle her with his “architectural” abilities. Tough luck for him if she brings Le Corbusier’s fastidiousnes to the assessment. A nest with “storeys” can suggest repeated slights and forced celibacy.

“If the nest is not selected, he starts building another at the base of the first one — sometimes, there would be two to three or even four nests,” points out ornithologist V. Santharam.

It is not clear what aspects of the nest the female baya weaver would be subjecting to intense scrutiny.

“They probably look for the strength of the material used or how lasting it could be,” Santharam conjectures.

Facts at a glance
  • 1. Taking cognisance of how the baya weaver (ploceus philippinus) is no longer seen in plentiful numbers in many of its known habitats, the Bombay Natural History Society brought the species under its citizens-driven Common Bird Monitoring Programme. Citizens are expected to record sightings of baya weaver and mail in the details to ibabnhs@gmail.com
  • 2. Baya weavers are a polygamous species, and in every breeding cycle the male of the species could multiple nests to woo females. Being a gregarious species, the nests are built in a colony, which explains why individual trees would be a target for intense nest-building. Choice of nesting trees are driven by considerations of food and water availability and safety from predators
  • 3. Nest-building ability being linked to the mate selection process, observations of young baya weavers cutting their nest-building tooth through a trail and error method before attempting the real thing do not come as a surprise
  • 4. Known as Thukanan-kuruvi in Tamil Nadu and and Thukanam-kuruvi in Kerala, this bird is a common sight on rural sections and their hanging nests are integral to the pastoral character of countrysides in these states. There are songs around this bird, with Thukanan Kuruvi Koodu from the Tamil film Vanambadi being arguably the most well-known in these parts

Fortunately, rejection and indifference are not at the centre of the baya weaver universe, and are only peripheral occurences. Usually, the nest passes muster, and the pact is sealed for the season. Sorry to be disappointing, but there is no forever mush in the baya-weaver scheme of things.

After accepting a nest and its builder — nay, weaver — the female would not reconsider her decision because she gets invested in the process. Alongside the male, she would hunker down to some nest-weaving herself, which makes the completed nest “theirs”, not “his” alone.

“The male baya weaver builds the nest up to what is called the helmet stage. It is called so because the top part resembles a helmet. The egg chamber and the passage — the long tube-like thing that leads to the bottom — are done after the female has approved of the male. She does much of the interior work and those kinds of things,” explains Santharam. “After construction of a nest and its acceptance, the male would go about the business of constructing another nest.” The male baya weaver obviously does not rest on his laurels.

“He has to build a new nest every season, because the nest itself cannot be reused — may be one-time use. Of course, a lot of work goes into it, but the material that is used is degradable. It is mostly grass and palm leaves and coconut fibres. It dries up after some time. Sometimes, by the time the next season comes, it would have fallen off and it would be used by munias,” says Santharam. “Additionally, they could be building a new nest every time to avoid parasites.”

There are also reported observations of male baya weavers refurbishing old nests, an option obviously contingent on the nest’s durability — however, there is sufficient reason to believe that they apply the reuse philosophy only in exigent conditions.

“There could be shortage of material. Or, shortage of time: The breeding season may be coming to an end, and the birds may see value in resorting to a short-cut.”

As nest-building performance is hardwired into the bird as a nuptial activity, they might be instinctively drawn to it, despite the drudgery of it. Palmyra trees tower over other options for nest-building. “They also nest on date palms. In the north, they use acacia trees. Right now, in Rishi Valley, two prosopis trees are favoured by baya weavers,” Santharam points out.

Even electric wires are a preferred perch for nest-building — the choice dictated by the fact that predators like snakes cannot access them. Choosing palmyra trees and tall thorny shrubs on the end of waterbodies, and building the nests on fronds and branches stretching into the waterbodies is dictated by the same logic.

(Resident Watch discusses resident birds found in Chennai and its surrounding districts)


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Printable version | Sep 23, 2021 2:33:13 AM | https://www.thehindu.com/sci-tech/energy-and-environment/resident-watchit-is-time-to-count-baya-weaver-nests/article35112417.ece

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