Predators such as jays, crows, raccoons, and cats, as well as the parasitic Brown-headed Cowbird, typically are not abundant in extensive forests. But when a forest is fragmented, predators and cowbirds gain more access to the woodland. The importance of large areas of continuous forest for maintaining forest-interior bird species has been demonstrated in the eastern United States during the past 15 years.

It is important to distinguish between a forest that is fragmented by agricultural or urban development and a forested landscape composed of a mosaic of mature and regenerating stands that results from timber harvesting. The first situation typically is more damaging to forest bird populations and may represent permanent habitat loss, whereas the latter situation may only cause a temporary reduction in habitat for forest-interior species that rely on mature forests. Furthermore, early successional forests do provide habitat for many bird species, including some Neotropical migrants that are declining. Nevertheless, forest-interior species that require mature forests are affected by both sources of fragmentation. In most large landscapes, the needs of early successional species can be met quickly through various sources of disturbance, including timber harvesting. Much more time, however, is required to develop suitable habitat for species that require mature forest. Effective conservation strategies must focus on maintaining adequate amounts of mature forest at any point in time.

BFL will provide us with data on the specific effects of forest fragmentation throughout the geographic ranges of many species of high-priority forest birds. These data will allow us to develop management recommendations, including estimates of minimum forest sizes, for many regions in North America. Region-specific management plans are particularly important for species with large ranges, over which the effects of fragmentation may vary.