GROWTH AND MORTALITY OF MALE AND FEMALE NESTLING HOUSE SPARROW PASSER DOMESTICUS IN ENGLAND

Schifferli L.



Abstract:

To find out whether the surplus of males found in various adult populatiOi1$ of House Sparrow is the resul t of an unbalanced sex ratio at fledging,the author studied the sex ratio of nestlings and growth and mortality of males and females in 397 chicks. There waS no evjdence far an unbalanced sex ratio and no seyual rlifferences in growth or morality were found. However, the sample to establish the sex ratio is much smaller than the ones cf adult populations in which an unequal ratio was established by others. Sex ratio and competition of nestlings in various species of birds are reviewed and discussed, It is suggested that an un balanced sex ratio in House Sparrow fledglings would occur only if food is abnormally poor, Then females which are smaller in size might be at a disadvantage in competition with their male siblings.