Linear sex ratio change in the clutch sequence of Melopsittacus undulatus

Philip, Sunitha A.; Oommen, Mathew M.; Baiju, K. V.
June 2010
Current Science (00113891);6/10/2010, Vol. 98 Issue 11, p1520
Academic Journal
Sex ratio, though a significant trait in natural selection, was left open in Darwin's explanations of natural selection. The first explanation for sex ratio being equal was that of Fisher. Since then, several instances of deviation from equal sex ratio have been described both in invertebrates and vertebrates. Melopsittacus undulatus is an exotic monogamous pet bird. Male and female on becoming sexually mature form a lifelong pair bond. During the breeding phase of their life (3-4 years) the female lays several egg clutches. Since 2005, 120 pair bonded sets in a sequence of five successive generations were reared. Data on male/female ratio of the 120 pairs showed a definite linear pattern of sex ratio shift among the offsprings across the clutch sequence of the pair bonds. This sex ratio shift is found to be directly correlated to the physiological status and reproductive behavioural courtship display of the females. These indicate a causal linkage between the sex ratio shift and female fecundity status.


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