Trends in breeding bird populations: A regional approach

Scientific research has used bird species as ecological indicators for assessing the quality of the surrounding landscape.  A majority of these studies focuses on a single habitat or ecosystem.  As anthropogenic disturbance, such as urban development and land conversion, threaten local habitats and communities, it is necessary to understand the role of ecological indicators on a regional landscape.  Birds, as indicators, reflect attributes of the local landscape, such as land use patterns and structural complexity.   Understanding the relationship between bird community composition and anthropogenic factors is important in understanding a species ability to persist across spatial and temporal scales.  I examined the long-term, landscape level change on the richness, abundance and composition of avian species in the Hudson River Valley, New York.  I analyzed trends in a 20-year dataset of bird observation in relation to changes in land use cover mapped from satellite imagery.  The objective of this research was to determine the effects (positive or negative) of land conversion on trends in breeding bird populations in a heavily developed corridor in Eastern, New York.  I grouped all identified breeding species into assemblages based on behavioral and life-history characteristics.  Assemblages allowed for a comparative study of bird community dynamics on a regional scale.   Results suggest that species composition remained stable between the years, but between year patterns in abundance and frequency varied among assemblages.  Grassland and forest specialist birds experienced the greatest decline, while generalist species, associated with urban developments and structures experienced the greatest growth.  Bird population changes paralleled change in land cover only when identifying specific assemblage relationships.  This suggests that overall trends in bird populations on a regional scale do not reflect changes on the regional landscape.  Trends in bird community composition and abundance may be effective indicators of landscape quality and configuration on more local scales.