Gut Morphology of Mallards in Relation to Diet Quality

Digestive organ lengths, weights, and volumes in each of three groups of mallards (Anas platyrhynchos) were determined at the end of a 21-day period, during which one group was fed turkey starter (control diet), another group was fed whole corn (low fiber content), and the third group was fed alfalfa pellets (high fiber content) to demonstrate the adaptive efficiency of the waterfowl gut to diets of varying quality. Food consumption by the alfalfa-fed ducks was significantly greater (P ( 0.01) than the other two groups. All digestive organs of the alfalfa-fed ducks were significantly larger (P < 0.01) than those of the cornand turkey starter-fed ducks at the end of the study. It is concluded that mallards can adapt rapidly to fibrous, relatively indigestible foods. This ability may have survival value when higher quality foods are unavailable or when food habits change rapidly during migrations. J. WILDL. MANAGE. 39(1):168-173 The ability of wild birds to survive on low quality foods (herein defined as foods relatively indigestible because of high fiber content), and the changes that occur in gut morphology and function in order to do so, have received relatively little attention. In gallinaceous birds, consumption of high quality diets (low fiber content, easily digested) is correlated with short guts and ceca, while consumption of low quality diets results in longer guts and ceca (Leopold 1953, Lewin 1963, Gardarsson 1971, Moss 1972, Pendergast and Boag 1973). These relationships need investigation in waterfowl. An increase in the efficiency of utilization of low quality foods may have survival value when favored, highly nutritious foods are not available. The purpose of this paper is to demonstrate the short term adaptive response of mallards to foods of varying quality by measuring differences in gut morphology among groups of these ducks fed different diets. I wish to thank D. G. Raveling for arranging financial support, for encouragement during the study, and for editorial assistance and guidance on the manuscript. R. G. Schwab provided the ducks, and R. Cole and K. Miller assisted me during the