That makes sense because previous work has shown that skinny female zebra finches are less likely to survive and reproduce than skinny males so when resources are poor, parents should prefer to produce sons.

ECONOMIST: Sexy sons, dutiful daughters | The

She was also able to demonstrate that the reddest males were indeed the choosiest about who got to do the laying, and that they did prefer bigger females.

ECONOMIST: Birds do it, bees do it | The