Variation in Shorebird Use of Diurnal, High-tide Roosts: How Consistently are Roosts Used?

In coastal environs during the non-breeding season, many shorebirds (suborder Charadrii) congregate at roosts, long considered to be traditional sites where flocks of individuals coalesce when high tides inundate feeding areas. Humboldt Bay, California was surveyed (9.5 months at roughly 10-d intervals) to assess temporal variation in incidence (proportion of 28 surveys birds used a roost), proportional abundance, concentrations, and repeatability (of seasonal average proportional abundances) of shorebird use of diurnal, high-tide roosts. Two hundred and forty roosting locations were identified and observations were made of 30 species. Fourteen species accounted for over 99% of observations. Shorebirds occurred at most roosts infrequently (