The comparative effects of landscape-level forest fragmentation, forest area and local habitat measures on Connecticut bird communities

I studied how breeding and wintering forest bird communities across
Connecticut responded to variation in habitat characteristics and
particularly such landscape attributes as forest fragmentation. I surveyed
birds at 1,815 points along 121 transects that traversed ca. 400 km of
forest. I also made 12705 habitat measurements at survey points and
computed areas of forest, non-forest, core forest and perimeter/area
ratios of forest for 31,550 ha of study area. I computed sampled species
richness and community density as well as individual species’ population
densities for each transect. Moreover, I classified species encountered as
to their nest site selection, macrohabitat use, microhabitat use,
migratory strategy and trophic affiliation. Based on observations of
36,702 summering individuals of 123 species and 13,742 wintering
individuals of 63 species, declines in community density occurred with
increasing fragmentation although species richness was often more closely
associated with habitat measures. Among landscape measures, forest
fragmentation had the closest association with summer community measures
67% of the time, strongly suggesting that fragmentation effects were the
predominant driver of such community patterns. However, short-distance
migrant density and richness, foraging generalist density and richness,
edge/successional species density and richness, habitat generalist
density, and Brown-headed Cowbird density showed little relationship to
landscape measures. The effects of fragmentation appeared to predominate
over those of simply forest extent in predicting summer and winter bird
community characteristics even in the comparatively extensive forests of
southern New England. Despite the importance of fragmentation effects,
community and individual species measures often tended to be more closely
associated with habitat measures than with those of fragmentation. In
addition, few summer or winter community measures or species patterns
showed any significant relationship to natural forest breaks. 
Winter community and species density patterns showed little relationship
to any landscape measures, with particularly elevation appearing to be a
principal driver of winter patterns.