It is widely assumed that female birds use non-photic supplemental cues,
including social factors, to fine-tune timing of egg-laying to local
conditions, but our knowledge of the nature of these social cues and how
they operate remains limited. We analyzed the relationship between a
female’s social environment (nearest neighbor distances, residency, female
-and- network familiarity, synchrony) and variation in timing of
egg-laying in European starlings (Sturnus vulgaris) using individual,
residual laying date (controlling for annual variation) and
temperature-independent residual laying date (accounting for the effect of
ambient temperature on laying date). Female social environment varied
systematically with overall spatial distribution of nest-boxes (linear vs
clumped boxes) but this was not associated with spatial variation in
laying date or temperature-independent residual laying date. We found no
evidence for any relationships between individual variation in social
environment and individual, residual laying date and only weak evidence
for any association with individual, temperature-independent residual
laying date. The latter was associated with a) nearest neighbor distances
in the linear habitat, with females nesting closer to neighbors laying
earlier than predicted by temperature, but not in the two clumped
habitats, and b) neighbor familiarity: females with an intermediate number
of returning females (3/8) laid closest to the predicted date. Finally,
despite the fact that synchrony was not associated with other social
environment metrics, females with lower laying synchrony among neighbors
laid earlier than predicted by temperature. This suggests that some
components of the female-female social environment could act as
supplemental cues for timing of egg-laying.