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| A multi agency project funded by US EPA's STAR Program | ||||||||
Results: Birds of Coastal Wetlands
Project Summary
During 2002-2003, researchers from the University of Wisconsin-Green Bay, University of Minnesota Duluth’s Natural Resources Research Institute, and Cornell University completed perhaps the most extensive field survey of breeding birds ever conducted in the Great Lakes coastal zone. More than 22 trained observers sampled 371 points in 215 wetland complexes, ranging from the western edge of Lake Superior in Minnesota to the eastern edge of Lake Ontario in New York State. Methods followed a standardized protocol used today by the Marsh Monitoring Program (Weeber and Vallianatos 2000).
Objectives of this project were to 1) develop a suite of scientifically robust, cost-effective indicators of ecological condition for the Great Lakes; 2) quantify the extent to which these indices are related to environmental pressure indicators such as land use characteristics; 3) use the results to improve the scientific framework for environmental monitoring programs in the Great Lakes basin.
Results
Observers recorded 155 bird species, approximately 54 of which are characteristic of wetland habitats. In order to assess the response of these species to environmental stress, a reference gradient was established based on a large number of environmental variables describing land cover, agriculture, human population density, roads, pollution emissions, and other human impacts. Multivariate statistical analysis was used to align the study sites along a single gradient ranging from 0 (maximally impacted by humans) to 10 (minimally impacted by humans). Responses of each bird species to the reference gradient (Figure 1) were plotted and described by a mathematical function illustrating the probability of finding the species in maximally degraded sites, the probability of finding the species in minimally degraded sites, the value along the reference gradient where the probability of finding the species is halfway between the maximum and minimum probabilities, and the overall steepness of the relationship. These SSD functions contain information about the response of each species to human impacts as well as the overall probability of finding the species in the study area. Once they have been derived, the SSD functions form the basis of a robust and highly flexible method for estimating ecological condition.
Probability-based Ecological Indicators
Ecological condition (C) for new sites can be derived through an ingenious method described by Hilborn and Mangel (1997). Rather than calculate C directly, one asks “what is the value of C that best reflects the SSD functions of the observed species?” Presence of sensitive bird species like those in Figure 1a and 1b, for example, indicates that the condition of a site must be high. An iterative process for calculating C can be implemented with the help of familiar computer software like Microsoft Excel. Eventually, a web-based utility might calculate C given any combination of species (not just birds) for which SSD functions are available. This project provides preliminary SSD functions that can be used today by environmental monitoring programs. All a user needs to do is apply results from standard bird counts, such as those from the Marsh Monitoring Program.
Computer iteration will yield a value of C ranging from 0 to 10, grounded in (but not simply mirroring) the reference gradient of human impact.
References
Hilborn, R. and Mangel, M. 1997. The ecological detective: confronting models with data, Monographs of Population Biology 28, Princeton University Press, New Jersey.
Weeber, R. C., And M. Vallianatos. 2000. The Marsh Monitoring Program 1995-1999. Monitoring Great Lakes wetlands and their amphibians and bird inhabitants. Published by Bird Studies Canada in cooperation with Environment Canada and U.S. Environmental Protection Agency.
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