Timing of egg-laying in relation to a female's social environment in European starlings.

This article investigates whether aspects of the female social environment act as supplemental cues influencing the timing of egg-laying in European starlings (Sturnus vulgaris). Using 20 years of breeding data from a semi-colonial population in British Columbia, Canada, the study analyzed five social metrics—nearest neighbor distances, residency, female familiarity, network familiarity, and laying synchrony—across different spatial nest-box arrangements (linear vs. clumped). While social environment varied significantly with nest spatial distribution, there was no consistent association between these social factors and absolute laying date; only weak evidence emerged when controlling for temperature effects, notably that females nesting closer to neighbors in linear habitats and those in networks with intermediate numbers of returning females laid closer to temperature-predicted dates. Additionally, females in groups with lower laying synchrony tended to lay earlier than predicted by temperature, suggesting limited but potential roles for female-female social cues in fine-tuning egg-laying timing beyond dominant environmental factors like photoperiod and temperature.