Habitat area requirements of breeding forest birds of the middle Atlantic states

Abstract

Conservation of birds requires an understanding of their nesting requirements, including area as well as structural characteristics of the habitat. Previous studies have shown that many neotropical migrant bird species seem to depend on extensive forested areas, but the specific area requirements of individual species have not been clarified sufflciently to aid in design and management of effective preserves. For this S-year study, bird and vegetation data were obtained at 469 points in forests ranging in area from 0.1 ha to more than 3,000 ha in Maryland and adjacent states. Data were analyzed first by stepwise regression to identify habitat factors that had the greatest influence on relative abundance of each bird species. In the relatively undisturbed mature forests studied, degree of isolation and area were significant predictors of relative abundance for more bird species than were any habitat variables. For species for which forest area was a significant predictor of abundance} we used logistic regression to examine the relationship between fcxrest area aIld the probability of detecting the species. In managing forest lands for wildlifel top priority should go toward providing for the needs of areasensitive or rare species rather than increasing species diversity per se. Avian species that occur in small and disturbed forests are generalists that are adapted to survival under edge conditions and need no special assistance frorn man. Forest reserves with thousands of hectares are required to have the highest probability of providing for the least common species of forest birds in a region. However, if preservation of large contiguous forest tracts is not a realistic optionS results of this study suggest 2 alternative approaches. First, if other habitat attributes also are eonsidered smaller forests may provide suitable breeding sites for relatively rare species. Second7 smaller tracts in close proximity to other forests may serve to attract or retain area-