Birds in a Tropical Mosaic - the Distribution of Bird Species in Relation to Vegetation Patterns

Abstract

Wilson and Bowman (1986) classified and mapped vegetation in a complex mosaic at Howard's Peninsula, Northern Territory. The relationship of bird distribution to this vegetation classification was considered through 10 repeat censuses of 5 replicate quadrats in each of 20 vegetation units. Censusing period was April-May. 118 bird species were recorded. Closed forests (3 units), mangroves (2 units) and swamplands (3 units) all had distinctive bird species compositions, but bird species showed a relatively poor relationship with the classification of woodland and grassland units. Eucalyptus woodlands regrowing after devastation by a cyclone in 1974 had similar bird species diversity and density to undamaged woodlands, though somewhat different bird species composition. Eucalyptus woodlands with a dense shrubby understorey had significantly greater bird density and species diversity than those with open or grassy understories and their bird species composition showed appreciable association with that of closed forests. Closed forest and, less so, mangrove units had highest diversity and density (despite their relatively small proportion in the study area and in the region generally), probably because they offered a wider range of foraging possibilities.