Length of stay and fat content of migrant semipalmated sandpipers in eastern Maine

Semipalmated Sandpipers (Calidris pusilla) stop at coastal staging areas in the Canadian maritime provinces and northeastern United States to replenish fat reserves before initiating a nonstop transoceanic flight of at least 3,200 km to wintering areas in South America. The relationship between estimated fat content at capture and length of stay (days between marking and last observation) of Semipalmated Sandpipers at one of these staging areas in eastern Maine was studied during 1980-1982. Total body mass and wing chord length were used to estimate fat content. When data were analyzed by week of initial capture, mean length of stay of both adults and juveniles decreased with increasing fat content. This supports the assumption that resumption of migration is affected by fat content at staging areas for long-distance nonstop flights. However, fat content at capture was a poor predictor of length of stay, which suggests that other factors are more important in determining length of stay.