ANALYSIS OF MIDWESTERN BREEDING BIRD POPULATION TRENDS - 1966-1993

Life-history traits associated with midwestern breeding bird populatio n trends were assessed using data from the North American Breeding Bir d Survey (BBS). Analyses of BBS population trends by bird-habitat asso ciation, nest location and migratory strategy groups showed that grass land bird species had exhibited more extensive population declines bet ween 1966 and 1993 than other groups of midwestern breeding bird speci es. Analysis of species representation in the midwestern BBS data, how ever, revealed significant biases in species representation based on h abitat associations. Wetland bird species are significantly underrepre sented on midwestern BBS routes, whereas urban and shrubland/early suc cessional 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 com pile a comprehensive pattern of population vends of midwestern breedin g birds.