How do birds identify cuckoo eggs laying in a nest?

It is not always easy to detect crow's nest eggs in the nest. But if you do not find out, you will have to pay a high price when you have to raise children for others. How birds distinguish eggs from 'impersonation' with their own eggs has long been a headache for scientists.

The problem still does not change when viewed with the eyes of our species. Only when people start to think about birds' views can they understand how to detect cuckoo eggs in a nest.

Marcel Honza of the Czech Academy of Sciences explains that birds can see UV wavelengths beyond our eyesight. Knowing that the eggs of many birds can reflect UV rays, Honza wonders if changing the egg's UV reflectance spectrum will affect the bird's ability to distinguish eggs and strange eggs and then remove the eggs. or not. Does the black-headed bird recognize and 'kick' the egg off if the UV reflectance differs from the wavelength at which its egg drive reflects?

(Photo: bbc.co.uk)

In collaboration with Lenka Polaèiková, Honza came to a forest to find out the reaction of the black-headed bird with the eggs laid on it. They published their findings on June 18 issue in The Journal of Experimental Biology.

But instead of examining the bird's reaction to the true cuckoo eggs, they found the egg of the abandoned black-headed bird, turning those eggs into impersonating eggs in the black-headed bird's nest. . After finding a very strong nest of black-headed eggs, they covered the eggs impersonating the UV barrier to change its appearance and coated Vazlin with other impersonating eggs that did not alter their ability to react. UV radiation before placing but the egg impersonates the new nest. Then they could only pray, hoping that the nest would not be swept away by the rain or avoid the visit of hungry hunters.

They have to wait 5 days to see if the parents remove the impersonating eggs.

Of the 16 eggs covered by Vazơlin, 11 were accepted by mother birds, 5 were discovered and discarded. Most of the black-headed birds' eggs cannot be distinguished from 'home' eggs and are accepted because of the same breed. However, it is another thing for egg hatching birds to impregnate with UV protection. 17 pairs of brooding broods removed the eggs that looked strange, they pecked on the eggshell until they created a hole large enough to poke the beak and carry the egg. Only 11 black-headed birds accept egg impersonation when the egg has been altered.

The egg's ability to reflect UV rays is very important to help the black-headed bird identify the impersonating egg . They removed more impudent eggs when Polaèiková and Honza covered eggs with UV shielding. By transforming the ability to reflect UV rays, the two men made the impersonal eggs stand out in the home egg.

Honza admitted that he was surprised that the ability to reflect UV rays had a big impact on the black-headed bird's identity. Knowing that the ability to reflect UV rays is key to making an impersonal egg acceptable, Honza is anxious to see if the cuckoo tries to become more ruthless than its victim by choosing an egg nest. The ability to reflect UV light is quite compatible with its eggs.