During the breeding season, male and female birds mate, lay eggs and give birth, and maintain their young. Birds usually breed more in summer in Bangladesh and India. This is because food is abundant in the summer and the chicks get enough food to survive the following seasons.
Although reproductive activity is normal for most species of birds, protecting their eggs and chicks can cause headaches in some birds.
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| Male Cuckoo |
In the world of birds, there is a special kind of bird called 'Brood Parasite', which means that these birds are parasites. Such birds do not usually build their nests, but lay their eggs in the nests of other birds and rely on the host birds to raise their young. This special behavior, which occurs through evolution, relieves the parasitic birds from the time and effort of rearing their young. And this time they use it to search for the nests of other birds, to plunder from those nests, and to give birth to more chicks. Although people have been aware of this Brood Parasitism for hundreds of years, no one has been able to explain exactly why and under what influence parasitic birds behave in this way.
Many of us have been hearing about cuckoos laying eggs in crows' homes since childhood. But most people are not aware of their movements, because they remain invisible.
Cuckoos are known for their cleverness when it comes to reproduction. They are brood parasites, which means that instead of building their own nests and raising their own young, they lay their eggs in the nests of other bird species.
In our country, the breeding season of crows is usually from the beginning of the monsoon to August. The breeding season of cuckoos is from March to September. See here that the breeding season of cuckoos is overlapping with the breeding season of crows. In other words, both crows and cuckoos have breeding seasons in certain months.
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| Female Cuckoo |
The cuckoo cleverly lays eggs in the crow's nest just because the number of crows' eggs is likely to be more than one. The pattern and color of the cuckoo's egg are similar to that of the crow's egg. Researchers have found that the color of the eggs of parasitic birds, such as cuckoos, imitates the eggs of other birds. For example, the color and shape of the eggs of the hawk cuckoo are exactly like the eggs of the birds in the jungle babbler. This evolution of egg color imitation has taken place mainly so that the host birds cannot identify their eggs.
Cuckoo eggs are usually a little smaller than crow eggs. But the crow can't catch it at all. And because the egg is small in size, it takes much less time to hatch. So the cuckoo's egg hatches first.
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| Crow chicks and eggs |
The crow usually lays an average of five eggs during the breeding season. One egg is laid every day. That means five eggs in five days. And just at this time, the cuckoo lays its eggs in the crow's nest. If the cuckoo lays eggs even a day before, then the cuckoo's eggs will be recognized by the crow and thrown away from the nest. And if the egg is laid after five days, the egg does not get enough care. So within one to five days after the crow starts laying eggs, the cuckoos lay their eggs in the crow's nest.
Before attacking the crow's home, the female cuckoo takes some precautions. In the beginning, their strategy is to attack the crow's nest and destroy it by dropping some eggs from their nest. But it can only do so when the crow's nest is empty. So at this time, the female cuckoo is sitting on a high branch of the tree and secretly keeps an eye on the crow's nest. The skin color of the female cuckoo is spotted like a hawk. As a result, they can easily hide behind the stalks and leaves. Just when he sees that there are no male or female crows in the nest, he will sit in the crow's nest to lay eggs. If the crows come before the eggs are laid, the crows chase them away. And just at that moment, he cleverly pressed a crow's egg from the crow's nest on his lips and flew away. In this way, after destroying one or two eggs from the crow's nest, the female cuckoo realizes the opportunity and lays her egg at some point.
The female cuckoo but not all eggs lay in the same crow's nest. He lays one egg at a time in different crows' nests.
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| Cuckoo chicks are dropping eggs of other birds |
Since the cuckoo's egg hatches before the crow's egg, the crow sees the cuckoo's offspring at the beginning and starts feeding and caring for it. Meanwhile, the baby cuckoo is also growing. Cuckoo chicks also often drop crow eggs. Because it is the instinct of the offspring of any parasitic bird, including the cuckoo. This reduces their food competition and gets more attention from the crows. And because their growth rate is much faster, they can fly much earlier than the crow's offsprings and leave the nest and start a new phase of life.
Cuckoos have evolved a number of strategies to ensure that their eggs are accepted and that their offspring are successfully raised by the host birds. For example:
Mimicry: Cuckoo eggs often mimic the appearance of the host bird's eggs, which helps to prevent the host from rejecting the cuckoo egg.
Timing: Cuckoos often lay their eggs when the host bird is away from the nest or distracted, which reduces the chances of the host detecting the cuckoo egg.
Egg destruction: Cuckoo chicks are known for destroying the host bird's eggs or chicks, which increases the chances of the host bird raising the cuckoo chick.
Begging behavior: Cuckoo chicks often have a distinctive call that mimics the calls of the host bird's chicks, which can trick the host bird into feeding the cuckoo chick as if it were its own.
Overall, cuckoos have evolved a remarkable level of adaptability and intelligence when it comes to their reproductive strategy. However, their behavior also has negative impacts on the populations of their host birds, which can lead to declines in those species.