The cuckoo is pitted against other birds in a survival race as it has to sharpen its egg mimicry skills to outwit the improved detection abilities of other birds.
Cambridge University researchers studied 248 nests in Tring, Hertfordshire that contained a cuckoo camouflaged egg among other eggs, according to the BBC.
Birds, unlike humans, can detect ultraviolet light wavelengths as they have four colour sensitive retinal cones rather than the human eye's three. They, therefore, have a broader visual spectrum than humans.
The Cambridge Universitiy's modelling of the bird's vision is called tetracolourspace.
During their avian research, the researchers were able to model the differences in the way the alien egg and the native egg were seen by the bird. The study used the tetracolourspace software to measure the variations between different birds' broods and the cuckoos' alien eggs.
The cuckoo lays an egg in a host nest and leaves the eggs among the native birds' for the chick to be brought up by other parents.
When the cuckoo chick hatches it ejects the other bird's eggs from the nest. The cuckoo is therefore seen as a predatory bird or a brood parasite as it is known.
However, according to research at Cambridge University reported by the BBC, the cuckoo's cover is not completely fail-safe. It seems that the cuckoo's eggs are more easily identified by some birds than others, independent of their simililarity.
The cuckoo can alter the colour of the egg it lays depending upon the host bird's eggs. For a redstart's nest it can lay a blue egg seeming to the human eye to be identical to the redstart's blue egg. However the cuckoo lays a white egg with brown speckles in a dunnock's nest even though the dunnock's egg is blue.
Mary Stoddard a PhD student in the Department of Zoology at Cambridge University and Dr Martin Stevens a fellow, studied the evolution of bird shell colour and pattern.
They set up tests to measure the similarity between the native and the alien eggs from a birds-eye viewpoint and to observe what happened to the cuckoo eggs.
They found that although the dunnock has a very different blue egg to the cuckoo's white with brown speckles, it is less likely than the redstart to evict the cuckoo egg.
The researchers have two explanations or hypotheses. Firstly, the dunnock may not have developed the detection survival skills of the redstart and is at an earlier stage of development in evolutionary defense against parasitism.
Secondly, the dunnock may detect the alien egg but consider it is safer to keep the egg than to evict it. In this case, the dunnock could decide that the risk of erroneously evicting one of its own eggs is higher than occasionally hosting a parastic egg.
Following the first hypothesis, researchers said that the cuckoo has had to evolve a better camouflaged egg for a redstart's nest than a dunnock's to be able to bluff their better detection skills.
Managing to detect the origins of an egg is crucial to the bird's future survival.
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