Abstract
Bird species richness (BSR) is affected by vegetation composition and habitat structure at both local and landscape scales. Urban development plays a pivotal role in avian diversity by inducing changes in the landscape structure and available resources. However, it is unclear how bird communities are responding in areas undergoing urban development, particularly in the non-breeding season when fewer studies take place. I examined the avian communities at 17 parks in urban (within established urban matrix >50% built, n=8) and exurban (residential developments in the adjacent grassland 5-20% built, n=9) areas of Rancho Cordova in Sacramento County, California during the non-breeding season. I collected data on bird species and abundance, conducting five line-transect surveys per park (85 total surveys). I investigated the factors influencing avian assemblage, including local habitat features such as percent land cover, number of trees, fruiting trees and tree species, tree height and diameter at breast height (DBH), park size, park age; and landscape features including percent land cover within 500m of parks and distance to riparian habitat. Fifty unique bird species, including 15 migrants, were observed in total. The BSR and avian abundance at urban and exurban parks was not significantly different, but community assemblages did differ significantly. Park area positively predicted BSR. Avian abundance was negatively predicted by park percent built cover, landscape percent water cover, and average number of fruiting trees. Species composition was associated with distance to river and landscape percent grass cover for all but one exurban park, and tree height, DBH and park and landscape percent tree cover for urban parks. The results suggest that in the non-breeding season, a variety of parks can support similar numbers, but different assemblages, of bird species.