The Correlation Between Ecology and Morphology in Deciduous Forest Passerine Birds

Abstract

We investigated the correspondence between feeding behavior and morphology among 19 species of passerine birds in the Hubbard Brook Experimental Forest, New Hampshire, using data in Holmes et al. (1979). Fourteen categories of foraging behavior were ordinated by reciprocal averaging. The first and second derived axes accounted for 61% of the total variance, and distinguished foraging substrate and maneuver. A morphological space was defined by eight external measurements. The correspondence between the positions of species in spaces defined by reciprocal averaging and morphology was determined by canonical correlation analysis. This analysis revealed two strong correlations: the first (R 2 = 0.94) related substrate utilization to the lengths of the tarsus and midtoe, and the second (R 2 = 0.70) related foraging maneuver to midtoe length. The canonical correlation analysis accounted for 83 and 74% of the variation on reciprocal averaging axes I and II; of the morphological variables, only tarsus (76%) and midtoe (64%) contributed strongly to the correlations. Therefore, although morphology predicts foraging behavior in this data set, considerable morphological variation is not related to the foraging variables that characterize the species' ecological relationships.