Responses of Breeding Bird Communities to Forest Fragmentation

Abstract

Field studies in eastern North America indicate that local densities of most forest-dwelling bird species are directly or indirectly influenced by forest insularization. Relevant site variables among those measured include patch area and isolation, tree stature and density, and development of herbaceous and shrub understorey. In general, highly migratory species that specialize on forest-interior habitat are adversely affected by forest fragmentation, whereas forest-edge species, particularly year-round inhabitants (here termed "residents"), tend to achieve higher local densities in fragmented forests. In eastern North America, rates of nest parasitism and nest predation are correlated with patch insularity. Several life history characteristics appear to make highly migratory species especially sensitive to these direct agents of reproductive failure.

The regional integrity of eastern North America's avifauna is maintained by frequent exchange of propagules among forest patches, few of which are sufficiently large to maintain a stable avifauna in vacuo. This pattern of frequent re-invasion.of small forested tracts may be less common at lower latitudes, where many bird species are sedentary habitat specialists.

In attempting to determine the optimal size and spatial arrangement of forest reserves for bird conservation, the absolute geometric scale of potential reserves, the functional "grain" of the regional habitat mosaic, the degree of ecological specialization of the bird species to be conserved,and their dispersal all must be conSidered.

Citation

Lynch, James F. 1987. Responses of Breeding Bird Communities to Forest Fragmentation. In: Aunders, Denis A.; Arnold, Graham W.; Burbidge, Andrew A.; Hopkins Angas J. M.; Beatty, Surrey, eds. Nature Conservation: The Role of Remnants of Native Vegetation, Sons Pty Limited. p. 123-140