North American Breeding Bird Survey Annual Summary, 1989

摘要

Population changes between 1988 and 1989 are estimated from North AmericanBreeding Bird Survey data for 251 bird species. Of these species, 60.5% had negative point estimates of trend. Population trends are summarized by State and within guilds of species to evaluate regional consistency of population changes within and among species. Declines are widespread among both regions and groups of species, and although the drought of 1988 has been suggested as a possible cause of the declines, a relation between drought intensity and population changes could not be documented. Long-term (1966-89) trends are also presented for comparison with the 1988-89 population changes.