Potential effect of early snowmelt on nestling growth and first-year apparent survival in an alpine bird

Climate change is shifting the environmental conditions during key life cycle events such as during reproduction. The shift in the environmental conditions can change for example the food availability and therewith influence growth and survival of offspring. We used nine years of ringing data of white-winged snowfinches Montifringilla nivalis nivalis, a high-elevation bird species, to assess how variation in temperature and snow conditions affected nestling growth and first-year apparent survival (probability that an individual survives and returns to the study area). We used linear mixed models and a path analysis to estimate the effect of environmental conditions on nestling growth and a multi-state mark-recapture model to estimate apparent survival. Nestlings raised during snowmelt tended to have slightly higher body mass, longer tarsi and longer wings than nestlings raised after snowmelt and apparent first-year survival was lower in years when snowfinches breed late relative to the timing of snowmelt. These findings suggest that advancing snowmelt may be associated with reduced offspring fitness and potentially contributed to observed population declines in this high‑elevation species.