The Effects of Habitat Structure and Floristics on the Densities of Bird Species in Wandoo Woodland.

Abstract

Censuses were taken in the springs of 3 consecutive years of the birds in twelve 2-ha sites in remnants of wandoo woodland in SW Western Australia. The sites were distributed between 3 vegetation types: (a) Eucalyptus wandoo open forest; (b) E. accedens open forest with Dryandra sessilis; and (c) Casuarina/Acacia low open forest. The 3 vegetation types had similar numbers of birds but different species diversities. Although the relative numbers in each group of species changed from year to year, the relative numbers were the same each year in the different vegetation types. The avian communities of (a) and (c) had a higher diversity than in (b). In (c) there were significantly fewer nectar and bark feeders than in (a) or (b), but more ground insectivores. In (a) there were significantly more parrots and leaf gleaners than in the other vegetation types, whereas (b) had very high numbers of nectar feeders but low numbers of ground/low shrub insectivores. Statistically significant relationships were established between the abundance of 13 of the most common bird species and habitat variables. These regressions showed that both floristics and structure strongly affected the abundance of a species. Between 42 and 95% of the variance in numbers was accounted for.