Reed College Canyon
Avian Response to Urban Landscapes: Implications for Restoration of the Reed Canyon
author: Brian John O'Shea
advisor: Robert Kaplan
ABSTRACT: This thesis evaluates the response of bird communities to urbanization, and extends this evaluation to generate predictions for the potential effect of restoration on the breeding bird community of the Reed canyon. Landscape fragmentation by human activity can impart a patchy spatial structure to populations of organisms in remaining habitat fragments. Certain bird species, however, are sensitive to habitat fragmentation, and may not maintain viable populations in highly fragmented landscapes. These species are especially likely to disappear from urban landscapes, because these landscapes are highly fragmented and productivity is low among populations within urban habitat fragments. My analysis of the literature indicates that productivity significantly affects several aspects of avian behavior that are associated with habitat occupancy. When this information is evaluated in the context of existing population models, it is apparent that habitat within which productivity is high will be preferentially occupied, while dispersing individuals should occupy the nearest available habitat.
I conclude from my analysis that native bird species that have declined substantially, or disappeared entirely, as breeders from the Portland area will not recolonize the Reed canyon, regardless of the apparent quality of habitat.