COMMUNAL ROOSTING AND FORAGING BEHAVIOR OF STAGING SANDHILL CRANES

Each spring more than 300,000 Sandhill Cranes (Grus canadensis) roost communally at night in river channels in the Platte River Valley of Ne braska and disperse at dawn to forage in agricultural fields. Cranes w ith central roosts had activity ranges double the size of those with p eripheral roosts; 42% of the birds changed activity ranges prior to th e onset of migration. Minimum daily flight distance generally increase d during the staging period. Cranes used native grassland and planted hayland more often than expected relative to their percentage of occur rence, and fed longest there; cornfields were under-utilized. These di fferences probably reflect, in part, (1) limited distribution of grass lands and haylands resulting in a greater energy expenditure to acquir e protein in the form of macroinvertebrates and (2) wider distribution of cornfields with adequate energy-rich foods but limited protein. Cr anes probably forage more efficiently and conserve energy by following conspecifics from communal roosts to local feeding grounds, by settli ng in fields where foraging flocks are already present, and by establi shing diurnal activity centers. Alert behavior varied with flock size but not as predicted from group size, presumably because predation of staging adult cranes is inconsequential.