Habitat, Behaviour and Morphology of Acrocephalus Warblers: An Integrated Analysis

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Abstract
Using six species of Acrocephalus warbler, we demonstrate the stepwise procedure of an ecomorphological study. First, we show that a correlation exists between habitat and morphology in these birds. Species inhabiting tall reeds in water like Great Reed Warbler A. arundinaceus and Reed Warbler A. scirpaceus, differ in three morphological complexes (hind limb, wing, bill) from species found in shorter vegetation like Sedge Warbler A. schoenobaenus and Aquatic Warbler A. paludicola. We demonstrate that the climbing behaviour of the six species investigated forms the necessary link between morphology and habitat structure. In double-choice experiments we scored the relative utilization of horizontal and vertical perches. The amount of vertical climbing correlated well with habitat variables as well as with morphology. Using multiple regression analyses we found that vertical climbing is best explained by the number of vertical stalks in a species'' habitat and increasing length of its hind toe. These results are discussed in relation to the climbing techniques used by Acrocephalus warblers.