Coping with habitat heterogeneity: the story of Mediterranean blue tits

A prerequisite for understanding adaptation is to understand how populations respond to environmental heterogeneity. We chose the blue tit Cyanistes caeruleus and Mediterranean habitat mosaics which exhibit a large diversity of habitats for analysing the effects of environmental heterogeneity on phenotypic variation. Three main factors of heterogeneity have been considered: (1) whether dominant tree species are deciduous or evergreen, (2) the geographic configuration of habitats and landscapes, and (3) the degree of infestation by parasites, which considerably varies in space. Several study sites equipped with nest-boxes and traps for collecting the droppings of caterpillars falling from the leaves of trees have been monitored over several decades in a series of habitats in mainland and insular (Corsica) landscapes. Depending on the geographic configuration of habitat patches within landscapes, the large phenotypic variation observed in many demographic, morphometric and behavioural traits has been shown to result either from a plastic response to habitat variation or from genetically determined specialisation to local habitats.

Jacques Blondel, J Ornithol (2007) 148 (Suppl 1):S3-S15