Photo courtesy: Wikipedia
Ranger Rani has seen many large families. She’s talking of birds, of course. Some birds lay many eggs at a time. And they nest with many other birds. Whenever Ranger Rani sees the busy, bird-filled swamps or trees, questions pop into her mind.
First, Ranger Rani wants to know if there’s a bird, any bird, which tries to take advantage of these busy birds. What kind of sneaky things do they do?
Second, Ranger Rani wants to know if the bird knows that another bird is taking advantage of them. How does it protect itself and young ones?
After some search, Ranger Rani found American coot to be a great example. Scientists have studied the coot better than other birds in the situation.
American coot lives in swamp and open water. They are omnivorous, eating plants, insects, fish, and other aquatic animals. The coot nest is hidden in the tall reeds along the rivers or swamps.
The world of a coot turns crazy during the breeding season. Birds- both male and female, fight fiercely to obtain a spot to build a nest for breeding. Then both the male and female birds fight their neighbors for a small territory. The parents have to obtain all their food from this small territory to feed their chicks.
Female coot lay about 6-11 eggs. Both male and female birds take turn to incubate. Now comes the tricky part. The females lay eggs in neighbors’ nest from time to time. Scientists call this behavior as conspecific brood parasitism.
Will the mother identify the imposter? Or will she feed the impostor at the cost of her own brood?
Scientists too had the same question. And they solved this by designing some unique experiments. Every coot lays eggs which have distinct fine details. More like human finger prints. A coot can actually recognize, by sight, that some eggs in their nest don’t belong to them.
Here’s what stumped the scientists. Even if the coot can distinguish very fine detail with eggs, they feed some other chick. Scratching you head? So were the scientists.
So, to understand why the bird was doing what it was, the scientists first put their heads together. They and came up with a hypothesis regarding why the birds were doing so. Some scientists hypothesized that recognition can be dangerous. There’s a chance that parents could mix-up recognition. That would mean the parents would reject their own children.
Did this mean that the coot should simply feed what hatched in the nest?
To answer this, scientists first observed the birds. They realized that in nests with eggs from another female, the eggs most likely to hatch first were the birds own. So, how does the bird decide who should be fed and who should be evicted?
Scientists transplanted hatchlings among nests. Much to the surprise of the scientists, the coot did have a way of recognizing their nestlings and others. If a strange chick arrived before their eggs hatched, the parents fed the strange chick and cared more for it. If the strange chick arrived at the same time as the other chicks in the nest, the coot didn’t discriminate between them.
Adult coot might also recognize the chicks which are famous for their crazy plumage. Parents could use these colors as a signature. Vocalizations could also help parents recognize their young.
The sweet singing Koel in India also lays its eggs in nests of many bird species. Is anyone interested in studying them?
