Comparative Ability of Northern Pintails, Gadwalls, and Northern Shovelers to Metabolize Foods

Abstract

Feeding trials were used to compare the ability of northern pintails (Anas acuta), gadwalls (A. strepera), and northern shovelers (A. clypeata) to metabolize energy from a turkey starter ration, alfalfa pellets, and common barnyardgrass (Echinochloa crusgalli) seeds. No differences (P > 0.05) were detected among the three species for any of the three foods (kg body weight/day basis), for dry matter intake (DMI), body weight gain (BWG), apparent metabolizable energy (AME), or metabolized energy (MEE) on any given diet consumed in quantities large enough to promote body weight gain. The AME content of alfalfa was 57% less than the value for turkey starter and 50% less than for barnyardgrass seeds. All three species metabolized more energy and gained weight faster when fed turkey starter. Energy modeling may be facilitated if additional research verifies that all species of dabbling ducks have equal ability to obtain energy from foods available to them in the wild. Behavioral and morphological factors may be more important in defining feeding niches than digestive physiology, at least for the three duck species tested, at the time of year of the experiments, and within the limits of the quality of foods used. J. WILDL. MANAGE. 48(2):362-370 Many species of dabbling ducks (Anatini) exhibit interspecific differences in food habits even though sharing the same habitats. Although some overlap among species exists during fall and winter, gadwalls eat a preponderance of vegetative plant parts and algae in marsh habitats, northern pintails consume seed diets in agricultural and marsh habitats, and northern shovelers normally consume planktonic foods by filter feeding in wetlands (Bellrose 1980:216, 274, 300). These species are closely related phylogenetically and are sympatric over much of their range. In addition to morphological (body size, neck length, bill shape) and behavioral (marsh vs. field feeding, tipping-up vs. surface skimming) adaptations for feeding, physiological adaptations have possibly evolved which allow maximum use of energy from foods regularly eaten as opposed to those seldom consumed. Digestive physiology, by influencing food selection, could be a factor in the separation of food habits, habitat selection, and reduction in competition for food re-