Evolution of colouration in bird eggs Essay Example | Topics and Well Written Essays - 2750 words

Evolution of colouration in bird ballock - Essay ExampleOne happen upon fact states that the more diversified a population becomes, the more likely it is to survive as a species. This increases its ability to occupy more territory and gain access to more sustenance, or to spread itself step forward and become more inconspicuous among predators. Several species of birds demonstrate this type of variation at the embryonic stage. The eggs they lay are coloured or spotted in particular ways, the complete reasons for which devote been jolly elusive to researchers for some time. In fact, birds are the only species that produce pigmented egg shells (Gosler, et al. 2005, p. 1105), and this leads scientists to believe that the pigmentation serves a determinable purpose. Such reasons as crypsis and the prevention of parasites corroborate been hypothesised. Other hypotheses have been based on sexual natural selection or on the chemical structure of the eggshell and its influence on eggs hell fragility and vulnerability. ford has also been suggested as a factor that influences egg colour. These hypotheses, though varied, have heavy implications on the evolution of the bird shells and can give insight into the reasons for the various pigmentations that birds eggs carry.Safety is a very important issue for birds when it is noted that their eggs are prone to different forms of predation and parasitism. Two types of brood parasitism exist. conspecific brood parasitism occurs when birds of similar species place their foreign eggs into the nest of a host. Interspecific brood parasitism occurs when birds of opposite species infiltrate the nest and place their own eggs in the clutch. This can be very redoubted to the existence of a particular avian species, since the some parasites are known to be vicious and ruthless. The well-nigh notorious of these parasites are cuckoos, and their parasitism is dangerous as they often hatch before the genuine brood and rout up aut hentic eggs from the nest, terminating that attempt of the species to reproduce. This is truer of some species than of other, depending on the type of predation suffered by each. The great depreciator (Parus major), for example, does not expel parasites from its nest, and this appears to be contingent on the fact that it is not a host to the European cuckoo parasite (Gosler, Higham and Reynolds, 2005. p. 1105-6). Village weavers, on the other hand, do remove foreign eggs from their nests, and have therefore to learn the appearance of their eggs (Collias, 1993, p. 684). The implication of this fact is that the weaver eggs must have progressively developed a distinctive appearance in order to facilitate recognition. It has been observed that west African village weavers spotted eggs have noticeable intraspecific differences, and hypotheses have been formed concerning the reasons for this. The scratch line spots on eggs might have been achieve by one incidence of patrimonial mutati on in the species, but this kind of spotting in weavers is now commonplace. Relying on the reasoning of the old paragraph, it was predicted that within the weavers clutches the diversity of colouration would be minimised in the absence of interspecific parasites and maximised in their presence. detective David Lahti found opportunity for an experiment involving these West African weavers in the fact that the species had