ECOMORPHOLOGICAL RELATIONSHIPS OF A GUILD OF GROUND-FORAGING BIRDS IN NORTHERN CALIFORNIA, USA

We studied habitat and morphological relationships of nine species of birds comprising a ground-foraging guild within four distinct locations in northern California. Although the nine species overlapped extensively in habitat use, we observed subtle differences among species in specific characteristics of the habitats they used. About 40% of all cases were classified to the correct species based on a discriminant analysis (DA) of habitats across all study areas. Classification success from DAs on habitats within study areas ranged from 42 to 66%. Morphologies of species differed to varying degrees as 91% of all cases were classified to correct species by a DA of morphological variables. This morphological separation suggested that each species used different modes of obtaining resources. We found only weak relationships between habitat use and morphology. Morphology predicted from 13.6 to 19.0% of the variation in habitat use within each study area and only 13.9% of the habitat variation across all study areas. Habitat predicted from 6.2 to 14.6% of the morphological variation within each study area and 6.9% across all study areas. We suggest that complimentary relationships of habitat and morphology enabled species within this guild to use unique sets of resources.