Abstract
The breeding phenology of species is intricately linked to the effect of environmental conditions. Environmental changes can lead to mismatches between the timing of reproduction and optimal conditions, posing challenges to reproductive success. Understanding the consequences of these mismatches on reproductive outcomes is crucial for assessing the adaptability of organisms to changing environmental conditions. While single-brooded bird spcecies have been extensively studied, multi-brooded species have received comparatively less attention, highlighting the necessity for further investigation in this area. This study aims to examine how shifts in spring temperature influence the first and optimum lay date, and how the strength and direction of selection gradient on the first lay date have changed in a metapopulation of house sparrows (Passer domesticus), a multi-brooded species. Throughout the study period, house sparrows consistently began laying eggs earlier each year, however, an effect of temperature on lay date was not observed.
A quadratic selection gradient model revealed increased selection pressure to start breeding earlier. Earlier breeders represented higher reproductive success in each breeding season. Although the strength of the selection gradient on the first lay date was not significantly different in the two habitat types, the fitness in non-farm islands was higher. This difference revealed the ecological demographic difference between the two habitats. The findings of this study helps to shed light on how a metapopulation of house sparrows changes their reproductive success in response to environmental changes. Additionally, the contrasting patterns observed between farm and non-farm islands suggest potential differences in environmental conditions or ecological dynamics that warrant further investigation.
