ECOLOGY/EVOLUTION

Regulating Food Intake

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Science  03 Feb 2006:
Vol. 311, Issue 5761, pp. 579
DOI: 10.1126/science.311.5761.579a

The kakapo—a bulky, ground-dwelling parrot endemic to New Zealand—is one of the world's most endangered birds, with just 83 living individuals. For the past 15 years, conservationists have attempted to increase the population by the supplementary feeding of female birds. However, although ad libitum feeding has indeed improved chick survival, it has also changed the sex ratio of offspring hatched, so that 70% of chicks are male: a proportion clearly at odds with conservation objectives.

Offspring sex ratio is known to be affected by environmental factors and maternal conditions in predictable ways; in particular, females in good condition tend to produce more sons. Robertson et al. have recently achieved near-parity in offspring sex ratio by regulating the amount of supplementary food given to females as a function of their predicted weight; feeding could not be abandoned entirely, because female kakapo need to weigh more than 1.5 kg in order to breed at all. Thus, the prospects for a conservation program have been enhanced by the application of theory from evolutionary biology. — AMS

Biol. Lett. 10/1098/rsbl.2005.0430 (2006).

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