Strive to survive: the skylark's ecology and physiology in an annual-cycle perspective

PhD ceremony: Mr. A. Hegemann, 11.00 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Strive to survive: the skylark's ecology and physiology in an annual-cycle perspective

Promotor(s): prof. B.L. Tieleman

Faculty: Mathematics and Natural Sciences

In his thesis Arne Hegemann integrates many different approaches and techniques and studies the ecology, behaviour and physiology of Skylarks throughout the complete annual cycle. Skylark populations in Europe are rapidly declining; in the Netherlands by 95% since the 1970s. Hegemann's unique integrative and multifaceted approach allows him to get a better ecological and evolutionary understanding of links between different stages of the annual cycle and of how birds combine the challenges of staying healthy with challenges like reproduction, moult or migration. Together with his coworkers Hegemann could demonstrate that Dutch Skylarks are partial migrants. Some birds winter on the breeding grounds, others migrate to SW Europe. The wintering strategy has consequences for the immune function of a bird and its future survival. He concentrated on immune function because a working immune system is crucial for survival. At the same time the immune system is costly; it requires energy and specific nutrients. Hegemann shows that immune function is variable throughout the year, depending on other activities (like reproduction) and environmental changes (like food supply). However, if a bird gets sick a standard and energetically costly response is required to ensure survival. These findings lead to a new concept of immune function in wild birds and point out the importance of environmental factors like food availability and disease pressure. Hegemann's fundamental studies provide several mechanistic links that might contribute to the population decline in agricultural areas. Conservation efforts can be improved by incorporating our results.