Large–scale geographical variation confirms that climate change causes birds to lay earlier

Christiaan Both, Aleksandr V. Artemyev, Bert Blaauw, Richard J. Cowie, Aarnoud J. Dekhuijzen, Tapio Eeva, Anders Enemar, Lars Gustafsson, Elena V. Ivankina, Antero Järvinen, Neil B. Metcalfe, N. Erik I. Nyholm, Jaime Potti, Pierre-Alain Ravussin, Juan Jose Sanz, Bengt Silverin, Fred M. Slater, Leonid V. Sokolov, János Török, Wolfgang Winkel, Jonathan Wright, Herwig Zang, Marcel E. Visser

Abstract

Advances in the phenology of organisms are often attributed to climate change, but alternatively, may reflect a publication bias towards advances and may be caused by environmental factors unrelated to climate change. Both factors are investigated using the breeding dates of 25 long–term studied populations of Ficedula flycatchers across Europe. Trends in spring temperature varied markedly between study sites, and across populations the advancement of laying date was stronger in areas where the spring temperatures increased more, giving support to the theory that climate change causally affects breeding date advancement.