Population trends of North American shorebirds based on the International Shorebird Survey

Shorebirds Charadrii are prime candidates for population decline because of their dependence on wetlands that are being lost at a rapid pace. Thirty-six of the 49 species of shorebirds that breed in North America spend most of the year in Latin America. Because populations of most species breed and winter at remote sites, it may be most feasible to monitor their numbers at migration stopovers. In this study, we used statistical trend analysis methods, developed for the North America Breeding Bird Survey, to analyze data on shorebird populations during southbound migration in the United States. Survey data were collected by volunteers in the International Shorebird Survey (ISS). The analyses indicate that whimbrels Numenius phaeopus, short-billed dowitchers Limnodromus griseus, and sanderlings Calidris alba have undergone statistically significant declines. Methodological concerns over both the ISS and the trend analysis procedures are discussed in detail and biological interpretations of the results are suggested.