Data from: Experimental cross-fostering of eggs reveals effects of territory quality on reproductive allocation

Parental and territory quality are often correlated in territorial birds,
and both factors influence the resources allocated to offspring.
Surprisingly, the relative contribution of these two components of
variation in parental investment remains obscure. We experimentally
decoupled the normal covariation between parental quality and territory
quality to test the hypothesis that territory quality influences female
prenatal and postnatal reproductive allocation. Territories were
categorized into low-, intermediate-, and high-quality based on fledging
success of nests over the previous six years (nesting sites are fixed in
space).To decouple covariation between territory quality and individual
quality, nestbox entrance size was increased on high-quality territories
and left small on poor-quality sites because house wrens (Troglodytes
aedon) prefer small over large entrances to their nest sites. We found a
significant prenatal effect of territory quality on nestling provisioning:
when reared on intermediate-quality territories, nestlings hatching from
eggs produced on low-quality territories were provisioned at a higher rate
than those hatching from eggs produced on high-quality territories. We
propose that the increased provisioning was brought about by increased
nestling begging mediated by a maternally derived compound, such as
corticosterone, transferred to the eggs of stressed females in
poor-quality habitat.