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How on earth did this kind of behaviour evolve ?..and how is it done ?...does the cuckoo control the colour of the egg by seeking out a nest first ? If so then how does the bird make the egg mimic the hosts eggs ? or does it just have to find a nest that the eggs look similar ?
And just how do you suppose that the origin of instinct could be an evolutionary impossibility?
"Female Cuckoos are divided into gentes, that is populations favouring a particular host species' nest and laying eggs which match those of that species in colour and pattern. The colour pattern is inherited from the female only, suggesting that it is carried on the sex-determining W chromosome (females are WZ, males ZZ). It is notable that most non-parasitic cuckoos lay white eggs, like most non-passerines other than ground nesters. The exception is in the case of the Dunnock, where the Cuckoo's egg has no resemblance to its hosts' blue eggs. This is thought to be because the Dunnock is a recent host, and has not yet acquired the ability to distinguish eggs. Male Cuckoos breed with females without regard to gens. This results in gene flow between the gentes and maintains a common gene pool for the species (except for the genes on the W chromosome)."