Birds in eucalypt and pine forests: Landscape alteration and its implications for research models of faunal habitat use

Most studies of faunal habitat fragmentation are based on a human perspective of the landscape in which landscape elements are classified as habitat and non-habitat. Moreover, many landscape models that define "habitat patches" assume that the same set of patches will be suitable for all taxa or a broad range of taxa. McIntyre and Hobbs [Conservation Biology 13 (1999) 1282] recently proposed a model in which landscapes can be classified according to the amount of habitat remaining and in which the remaining habitat can correspond to a continuum or gradient of modification. The perception of a landscape as being intact, variegated, fragmented or relictual [sensu Conservation Biology 13 (1999)] will depend on the capacity of individual species to utilise modified habitat. We suggest that although the continuum concept of habitat use is reasonably well established for plants, faunal studies have often ignored the notion of a gradient of habitat use and have classified landscape areas simplistically and inappropriately as either habitat or non-habitat. Data on birds in southeastern Australia are used to illustrate how the binary view of habitat can be incorrect. Birds were sampled in landscapes that ranged from intact to relictual as defined from an anthropocentric perspective. Our data: (1) illustrated a wide range of bird responses to habitat modification including many that might have been overlooked using a simple binomial approach to habitat classification, and (2) highlighted the fact that the way in which humans perceive landscapes may not correspond to how some elements of the biota perceive the same landscape. Viewing landscapes as a species-specific gradient of states of remaining habitat and condition has important implications for undertaking studies of human impacts on biodiversity and also integrating conservation considerations in production environments. It also challenges the effectiveness of "quick fixes" such as species-based biodiversity surrogates schemes and the uncritical use of generic landscape indices to save "habitat" because the assumption that all species will conform to the same landscape pattern will not hold.