Tuesday, September 19, 2006


Bird moms manipulate birth order to protect sons (PNAS - Badyaev)

Smithsonian Tropical Research Institute Carpodacus mexicanus (Evolution Research: John Latter / Jorolat)

Protecting her kids from peril is the job of every good mom.

When marauding mites turn up in a house finch's nest, she shelters her sons from the blood-suckers by laying male eggs later than those containing their sturdier sisters, according to new research.

Making sure the vulnerable baby boys are exposed to mites for a shorter period allows both the sons and the daughters to survive long enough to leave the nest.

'Sons are more sensitive to the mites than daughters,' said Alexander V. Badyaev (homepage) of The University of Arizona in Tucson. 'Mothers minimize sons' exposure to mites by laying male eggs later than female eggs. As a result, the males are in the nest fewer days.'

Even so, the male chicks that grow up during mite season end up just as big as ones from the mite-free time of the year.

'We've found a mechanism by which duration of growth can be adjusted to a changing risk of mortality,' said Badyaev, a UA assistant professor of ecology and evolutionary biology. He added that this is the first documentation that maternal manipulation of both ovulation and growth influences the duration of development in birds. [Evolution]
Based on the Proceedings of the National Academy of Sciences (PNAS) paper "Sex-biased maternal effects reduce ectoparasite-induced mortality in a passerine bird" (Abstract)

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