Document Type

Honors Project On-Campus Access Only

Abstract

The study of the ecological landscape is vital to understanding processes of disturbance, particularly in patchy urban and urbanizing areas. The study of urban ecosystems is becoming increasingly important as urban and suburban development stretch into previously rural areas. In studying urban areas, birds have frequently been used as biological indicators of habitat quality. Urban development has often been shown to decrease habitat quality for birds, but old fields (abandoned agricultural fields) frequently function as refuges for a variety of grassland birds. The purpose of this study was to examine the effects of traffic density and urban development on old field birds in the Twin Cities Metro Area in east central Minnesota

Old field bird communities along a gradient of urban development in east central Minnesota were studied during post-breeding in 2005 and peak breeding season in 2006. Bird census data were collected both summers and analyzed using direct and indirect gradient analysis. In order to better understand the patterns of bird usage of old fields, a variety of environmental variables were measured, which describe the characteristics of the fields and surrounding landscape. GIS analysis and field data collection were used to gather these environmental variables. They included hourly traffic density, vegetation cover at each site, and landscape metrics such as percent surrounding agricultural lands at various spatial scales for each study site.

The results showed that traffic density plays a dominant role in the effects of the gradient of urban development on old field birds. These bird communities respond differently to the gradient of urban development during peak breeding season and post-breeding season, with larger, more diverse communities in low-traffic fields during the breeding season and larger communities in high-traffic fields post-breeding season. Agricultural fields may support grassland bird species as secondary habitat, but their presence within the landscape may contribute to decreasing use of old fields by ecotone bird species. These findings indicate that future urban development, decreasing agricultural lands and increasing traffic density, will significantly decrease breeding bird abundance and species richness in old field bird populations unless management actions are taken. Native grassland and ecotone species will be particularly impacted by these landscape changes. However, landscape metrics point to a relatively small zone of landscape influence of approximately 100 meters. If old fields are buffered from traffic and development during the breeding season, old field birds may be able to maintain viable populations within an urban landscape.

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