Determining the Diet of Whooping Cranes (Grus americana) Through Field Measurements

Abstract. Though an important measure for ecological studies, obtaining foraging data through direct observation is rarely assessed independently. Using field measurements (foraging habitat, food acquisition behavior, and food manipulation time), the summer diet of Whooping Cranes (Grus americana) in Wisconsin, USA, was determined; foods consumed based on foraging behavior were identified; and ingestion for Sandhill Cranes (Antigone canadensis) was assessed. Based on 102 observations, Whooping Cranes occupying six territories consumed 17 food items (verified with images), of which 90 samples from nine foods were modeled. Food manipulation time predicted food size: ln(y) = 3.50 + 0.45ln(x) - 0.05 ln(x2) (r2 = 0.63, P< 0.001). Classification tree analysis identified consumed food using foraging behavior (error rate = 17%). A schematic model with the same three behavioral variables and an additional variable of direct observation identified 93% of 90 items. With Sandhill Cranes, observed swallows predicted a...