Leg Morphology and Feeding Postures in Four Parus Species: An Experimental Ecomorphological Approach

Abstract

The foraging behavior of four Parus species feeding at artificial feeders was studied, while controlling for ecological variables related to patch characteristics (food quality, food access, and escape distance to the nearest refuge). Hindlimb morphology (osteology and myology) was analyzed and compared with foraging postures at feeders. Using the Long—Tailed Tit as an appropriate outgroup for comparison, and considering functional changes associated with morphological changes, we demonstrated the existence of clear ecomorphological patterns relating foraging postures and hindlimb morphology in the four Parus species studied. The Blue Tit uses hanging postures preferably and its hindlimb morphology is modified for helping leg flexion. The Crested Tit more often stands and its hindlimb morphology is modified to aid leg extension. Great and Coal Tits are ecologically and morphologically intermediate between the two former species. Our results show morphology as a determinant of locomotion mode. Since foraging postures are tightly associated with substrate use, then morphology should be considered when studying pressures determining community organization. Our proposed integrative method for dealing with ecomorphology can be valuable in demonstrating the adaptiveness of morphological structures in phylogenetically and ecologically related species.