Avian diversity and abundance on a suburban university campus: Are trees enough to make a forest from a bird’s point of view?
As the human population continues to grow and alter habitats across the planet, the study of animals and plants in human-dominated landscapes has become a new and important focus of behavioral and ecological biology. Birds are excellent indicators of the ecological health and overall diversity of habitats because they are easily detectable and mobile enough to flee poor habitats and quickly repopulate restored habitats. The purpose of this study is to use the habitat preferences of birds on and near the suburban campus of SUNY New Paltz, Ulster County, NY, to examine the effects of small-scale urbanization on avian habitat quality. The quads on our campus include a number of large trees and we aim to evaluate whether or not the campus trees offer enough habitat to simulate healthy forests. For this first phase of the project, we used point counts and tree sampling to compare breeding bird and tree diversity and abundance at three locations on campus (wooded quads) with those at three nearby forest locations (natural forest fragments).
Bird species richness was about twice as high at forest sites than campus sites (mean richness forest = 19 and campus = 9.3; student’s t =6.65, p = 0.003). Forest sites included many species of neotropical migrants and no invasive species. Bird abundance was higher at campus sites (mean abundance per species forest = 0.67 and campus = 1.6; Student’s t =-4.25, p = 0.04), due in part to high numbers of invasive house sparrows and European starlings. This finding echoes the results of many studies that have found a decrease in bird diversity and an increase in bird abundance in urban city centers, and indicates that our campus trees are not providing sufficient habitat on campus for native birds. Bird species richness was not related to tree diversity (Pearson correlation: r =- 0.066, p = 0.901), because tree species richness was similar across sites due to the diversity of ornamental tree species planted on campus. On average, campus trees had larger diameters, but were growing at lower densities than those at forest sites. Bird diversity was correlated with tree density (Pearson correlation: r = 0.820, p = 0.045), suggesting that increasing the number and density of trees on campus might create more suitable habitat for native and migratory birds.