ANALYSIS OF MIDWESTERN BREEDING BIRD POPULATION TRENDS - 1966-1993

Life-history traits associated with midwestern breeding bird population trends were assessed using data from the North American Breeding Bird Survey (BBS). Analyses of BBS population trends by bird-habitat association, nest location and migratory strategy groups showed that grassland bird species had exhibited more extensive population declines between 1966 and 1993 than other groups of midwestern breeding bird species. Analysis of species representation in the midwestern BBS data, however, revealed significant biases in species representation based on habitat associations. Wetland bird species are significantly underrepresented on midwestern BBS routes, whereas urban and shrubland/early successional bird species are overrepresented relative to other groups of bird species. Because of these differences in species representation, additional surveys and monitoring programs are needed in order to compile a comprehensive pattern of population vends of midwestern breeding birds.