Do fragmented coastal heathlands have habitat value to birds in eastern Australia?

Abstract

This study investigated the effects of habitat clearance and fragmentation on birds of coastal heathlands in subtropical eastern Australia. Abundance and species composition were compared among two types of cleared habitat (residential suburbs and sugar cane cropland) and four sizes of heathland remnant (1–2 ha, 5–10 ha, 20–50 ha and >500 ha) in summer and winter. Cleared land contained a distinctly different bird species assemblage from heathland remnants. Residential sites contained a distinct suite of species consistent with that described for ‘open/developed land’ habitat elsewhere in the region. In contrast, cane cropland supported very few species. Heathland remnants >500 ha contained high densities of ‘natural-vegetation-dependent’ species, whereas species of open/developed land were absent. Remnants of 1–2 ha had lowered densities of many natural-vegetation-dependent species, and a relatively high abundance of open/developed land species. Some of the avifaunal differences in the >500-ha remnants and 5–50-ha range are probably due to confounding of remnant size with habitat, resulting from selective clearing of the landscape. Most of the heathland birds were intolerant of the matrix habitat (residential and cane cropland), but tolerant of decreased remnant area, down to a threshold of about 5 ha. However, the distinctive floristic associations of heathland vegetation are dependent on an environmental regime (low nutrient, low pH, fire, in some cases inundation) that is unlikely to persist in remnants tens of hectares in size, and longer-term declines in heathland birds, are predicted.