Feeding and Digestive Organ Size in Breeding Lesser Snow Geese

Abstract

Abstract The Lesser Snow Geese that nest at the McConnell River, Northwest Territories, feed heavily before arriving on the breeding grounds. During laying and early incubation, feeding declines to low levels but increases slightly during late incubation. After their eggs hatch the geese greatly increase their food intake. These changes in feeding activity are correlated with changes in the average sizes of four digestive organs (pancreas, liver, gizzard, and intestine). The large digestive organs characteristic of arriving and post-hatch geese are due to hyperphagia. Previously reported situations that produced decreased size of avian digestive organs did not account for that condition in incubating geese. The decrease in size of digestive organs during incubation is claimed to be innate; its evolution is discussed.