Over 16 field seasons, between 1981 and 2006, nearly 20,000 migrant Semipalmated Sandpipers were captured, weighed, and their bills and wings measured during the fall stopover in the Bay of Fundy. Annual mean bill and wing lengths declined over the course of the study. As eastern Semipalmated Sandpipers have longer bills and wings than those from the west, we interpret the decline to be the result of a reduced proportion of eastern birds in our samples. Semipalmated Sandpiper populations are in decline in North America, and our data suggest that the decline may be more severe in the eastern part of their breeding range. Body mass and size-adjusted mass at the migratory stopover study site have not declined during the study, suggesting that feeding conditions have not deteriorated there. Possibly, differing conditions experienced on the breeding grounds or overwintering areas may explain why eastern populations of Semipalmated Sandpipers may be declining more severely than those from the west.