Abstract
Bird populations are today affected by large-scale climate changes. In order to understand how birds respond to these changes we need to understand how the environment affects different reproductive variables in wild birds. The major stepping-stone from environmental variables to reproductive life-history traits is via a cascade of neuroendocrine and endocrine processes, and it is the plasticity in these mechanisms that determine the degree of constrainment in the individual´s capacity to respond to environmental changes adaptively. The photoperiodic great tit is a species that during the last 50-years has extended its breeding range enormously to the north. This must have profound implications for the mechanisms by which the central nervous system perceives environmental signals, and transduce them into neuroendocrine and endocrine secretions that then regulate phenotypic changes. The aim with this project is to test (in the field and in the lab) predictions from a theoretical, mathematical model (based on existing demographic data) suggesting that northern populations of great tits are less sensitive in their neuroendocrine, endocrine and gonadal responses to changes in environmental cues, such as temperature or food abundance than southern populations are. In the long run this means that birds breeding at northern latitudes will breed at less and less optimal conditions the further global warming goes - unless birds rapidly adapt to the new environmental conditions.
Sweden