Convergence in Aerially Feeding Insectivorous Birds

Abstract

An analysis of bill, forelimb and hindlimb skeletal morphology of four families of aerial foraging birds (apodids, caprimulgids, glareolids and hirundinids) and closest related families of non-aerial foragers (charadriids and parids) was made to investigate possible convergence for acrial feeding in groups with very different phylogenetic histories. The correlated evolution of foraging mode and skeletal morphology was studied using the phylogenetically independent contrasts method in order to test a prediction of convergent evolution, and to assess the adaptive significance of morphological variation. Results show the existence of an ecomorphological pattern relating the aerial feeding technique with short, wide and flat bills, and short legs and pclvcs. We demonstrate that to properly test convergent hypotheses the effect of 'common ancestry' must be taken into account, otherwise spurious relationships can be obtained. This study also shows that in spite of the ecomorphological pattern shared for aerial foragers, they are segregated in the morphological space. We suggest the existence of some design limitations (phylogenetic constraints) which make certain morphological responses more likely than others.