Dietary Selectivity in Relation to Availability and Quality of Food for Goslings of Cackling Geese

Abstract

Abstract Food selection by and diet of Cackling Goose (Branta canadensis minima) goslings were studied in relation to the quality and availability of food during brood rearing, 1977-1979. Arrowgrass (Triglochin palustris) was the most important food in the diet of goslings before wing-molt of adults and sometimes during molt. Carex mackenziei was the most common sedge in the diet but was less important than arrowgrass. Leaves of other species were relatively unimportant during premolt. Arrowgrass declined, while Carex seeds and crowberries (Empetrum nigrum) increased, in the diet as brood rearing progressed. Arrowgrass was highly preferred, whereas other sedges and grasses (except C. mackenziei) were avoided in areas for which both availability and consumption were measured. Preference for arrowgrass was related to its higher protein and energy content and lower cell-wall content compared to other forage species. Thus, geese benefitted nutritionally from selecting their preferred diet. Seeds and berries contained high levels of lipids and carbohydrates relative to green leaves. Less arrowgrass was consumed in a year when brood densities were higher than in the other 2 years of the study. Arrowgrass availability declined as brood rearing progressed in another year. Thus, Cackling Geese may have been reducing the availability of their most nutritious food, at least at high brood densities. Food quality in breeding areas may be influencing population dynamics of geese despite the high overall availability of green plants.