Mother's darlings

Testosterone in zebra finch eggs related to the attractiveness of the male

source: Matt Walker
New Scientist October 9 1999 p18

Researchers at the University of Paris, France, and St Andrews University, Britain, have found that female zebra finches deposit more testosterone in eggs from liasons with males they favour. This extra testosterone makes chicks more likely to hatch earlier, grow faster, and beg for food in a more insistent way. The favoured males had red bands attached to their legs, and female zebra finches find these bands attractive. The females may have been more aroused by the red-banded males, which may have boosted their hormone levels, so the levels in their eggs. This finding means that it is difficult to separate the impact of paternal genes from the mother's contribution.