The effect of temperature on productivity of birds in Sweden and Finland

Sammanfattning: Anthropogenic climate change is one of the most important factors influencing population growth and survival. Therefore, to be able to predict the effect of climate change on ecosystem composition and function, it is important to understand its effect on demographic variables, such as productivity. As a measure of productivity, I related the proportion of yearling birds captured during bird ringing in southern Sweden with mean temperature during the breeding season. I then compared the relationship between temperature and productivity for species with different traits regarding number of broods produced per season, thermal niches and migration behaviours. For most species (72%), productivity positively related to temperature during the breeding season. The relationship was strongest for species with the ability to vary the number of broods per year and species with a warmer thermal niche, whereas there was no difference between long-distance migratory and short-distance migratory species. The results suggest that, for some bird species in the study area, climate warming can increase population sizes. However, long-term effects of climate change may be different than the interannual fluctuations of temperature considered in this study, especially when interacting effects of habitat losses are taken into account.