Feeding ecology of sandhill cranes during spring migration in Nebraska

We studied the food habits of midcontinent sandhill cranes (Grus canadensis) during spring 1978 and 1979 at their primary staging area along the Platte River and compared population food and foraging habitat requirements with availability. Crane diets varied among the 3 principal foraging habitats, but not between sexes, ages, or years. Cranes feeding in cornfields ate >99% corn (total dry wt); those feeding in native grasslands and alfalfa fields consumed 79-99% invertebrates. The composite diet of cranes was 97% corn and 3% invertebrates, including 2% earthworms, 0.5% snails, and 0.5% insects. Presumably, corn provided energy, whereas invertebrates from grasslands and alfalfa fields provided supplemental nutrients to compensate for protein and calcium deficiencies in corn. The mean density of waste corn decreased (P < 0.05) from 399 kg/ha in November, to 205 kg/ha in early March, to 128 kg/ha after departure of the cranes. Simulations of population energetics indicated that 450,000-550,000 cranes would consume 20-25% of the waste corn available in the Platte River Valley during spring. Corn availability is unlikely to affect crane use of staging areas unless cropping practices or fall tillage reduce the acreage of harvested cornfields by >50%. Management by burning, haying, and grazing is compatible with crane use of grasslands, and reduced-till farming could benefit cranes by increasing invertebrate populations.