Migration Chronology, Sex Ratio, and Body Mass of Least Sandpipers in British Columbia

We banded, weighed, and measured 2147 Least Sandpipers (Calidris minutilla) migrating across the Fraser River delta in 1977-1987 and Sidney Island in 1990-1993. The adult migration from late June to early August overlapped the juvenile migration between late July and late September. The mean body mass of adult females on their northward migration was not significantly greater than on their southward migration. Samples sizes of northward migrating males were too small to draw similar comparisons. Adults were not significantly heavier than juveniles on the southward migration. Mean body masses were greatest in the third week of July among adults and in the third week of August among juveniles. The average length of stay during migration was estimated to be about five days in autumn.