Landscape dynamics of bird communities in relation to mass flowering in some eucalypt forests of central Victoria, Australia

The large-scale dynamics of bird communities in central Victoria, Australia, were studied in relation to eucalypt flowering by recording community changes throughout the annual cycle in sites north and south of the Great Dividing Range (GDR). Two kinds of forest habitat were considered, one of which flowers profusely in winter ('ironbark') while the other flowers little but over the warmer months ('stringybark'). There were eight sites, two of each habitat in both the northern and southern regions. In the absence of flowering in ironbark sites during summer, the avian communities of both kinds of habitat are virtually the same in each region. However, the sets of communities in each region differ significantly from one another at this time. With the onset of winter flowering, avian community composition in ironbark habitats in each region diverges greatly from the non-flowering ironbark and stringybark communities, but converges back to those communities as flowering declines. Most of these changes are due to the influx of high densities of nectarivores, especially honeyeaters and lorikeets. Such influxes in stringybark habitats did not occur, probably because the flowering intensity was at most an order of magnitude less than that in ironbark sites. The results show the dramatic impact that eucalypt flowering has on avian communities in south-eastern Australia, and the influence of habitat differences. Thus, although nectarivores move into the northern region of the study area to capitulize on winter flowering, they show high habitat specificity and virtually avoid the non-flowering stringybark habitats. The results are discussed in terms of landscape and regional dynamics of birds and the possible interactions among avian sub-communities (the 'nectarivores' and 'non-nectarivores').