Data from: Disentangling genetic and prenatal sources of familial resemblance across ontogeny in a wild passerine.

Cross-fostering experiments are widely used by quantitative geneticists to
study genetics and by behavioral ecologists to study the effects of
prenatal in- vestment. Generally, the effects of genes and prenatal
investment are confounded and the interpretation given to such experiments
is largely dependent on the in- terests of the researcher. Using a
large-scale well controlled experiment on a wild population of blue tits
(Cyanistes caeruleus) we are able to partition variation in body mass
across ontogeny into the effects of genes and the effects of between-
clutch variation in egg characteristics. We show that although egg effects
are important early in ontogeny they quickly dissipate, suggesting that
the genetic interpretation of cross-fostering experiments may be
preferable for many types of trait. However, the heritability of body mass
is smaller than has previously been reported. Our results suggest that
this is due to a combination of control- ling postnatal environmental
effects more carefully and accounting for viability selection operating
early in ontogeny.