BBC NEWS | Science & Environment | Finches choose sex of offspring

BBC NEWS | Science & Environment | Finches choose sex of offspring: "Colourful Gouldian finches can judge if a mate is genetically compatible just by looking at its head.

A female that mates with a male with the same colouring lays eggs that hatch much healthier chicks.

This new study has found that, when the female finches mate with a male that has a different head colour, they select the sex of their offspring - giving their chicks a better chance of survival."

Two interesting questions arise -- how much "compatibility" information is encoded in a peacock's feathers? How many other traits can animals explicitly select for?