Seasonal Changes in Composition, Abundance and Foraging Behavior of Birds in the Snowy Mountains

Abstract

The composition, relative abundance and foraging behaviour of birds were recorded in subalpine and alpine environments in the Snowy Mountains throughout the period 1977-1988. The numbers of species and individuals recorded decreased markedly with increasing altitude, with 63 species being observed regularly in the subalpine zone and 29 of these also occurring in the alpine zone. Bird populations showed a marked decline during autumn and winter, particularly after snow cover was established. All birds left the alpine zone for at least part of the winter period, and only six species remained throughout winter in the subalpine zone. Extensive snow-cover modified bird foraging behaviour by preventing feeding in the shrub layer and at ground level, thus restricting feeding to the trunks and fliage of snow gums and to the surface of the snow. This led to a reduction in bird diversity when compared to nearby snow-free montane habitats. In late winter and early spring an increase in arthropod fall-out on the remaining snow and flowering by the bird-pollinated shrub Grevillea victoriae, provided additional food for insectivorous birds and nectar feeders. With increased availability of food resources and foraging niches during spring and early summer high numbers of migratory birds were attracted to the region.