A Trophic Comparison of Avifaunas

A trophic comparison of Avifaunas. Syst. Zool. 21:135–150. This paper presents an attempt to compare the passerine and near-passerine bird faunas of the six faunal regions on a trophic basis. Indices of similarity are calculated using: a) the importance (percentage of total species) of families in the areas, and b) the importance of different trophic roles in the areas. The importance values for trophic roles were calculated by multiplying the importance values of the families by indices for the importance of applicable trophic roles for each family and summing the values for each trophic role in each region. The faunal regions showed much higher similarity indices when compared on a trophic rather than a taxonomic basis. Also, the geographic patterns of taxonomic similarity are different from that for trophic similarity. High trophic similarity is related to the major ecological division “temperate” versus “tropical” rather than to the geographical proximity. An examination of the individual trophic roles reveals several facts. While some, such as gleaning invertebrates from foliage, have little variation in importance from region to region, others such as nectivory show high degrees of difference. Other roles with intermediate variability show individual discrepancies, such as the paucity of ground-feeding insectivores in the Australian region. Possible reasons for some of these phenomena are suggested. The families of birds that are specialists in or major contributors to the different trophic roles are surveyed to provide a number of examples of “ecological equivalence” between taxonomically remote groups. This ecological equivalence is often reflected in convergent moiphology and behavior patterns.