Changes in Diet and Body Composition of Canada Geese before Spring Migration

• Published in: The Auk 1981-01, Vol.98 (1), p.65-79
• Main Authors: McLandress, M. Robert, Raveling, Dennis G.
• Format: Article
• Language: English
• Subjects: Body composition; Body weight; Branta canadensis maxima; Corn; Female animals; Food availability; Geese; Lipids; Male animals; Minerals; Seasonal migration
• ISSN: 0004-8038; 1938-4254

Changes in diet and body composition of Giant Canada Geese (Branta canadensis maxima) were studied before geese initiated spring migration in early April. During the period of hyperphagia in March, body weight of female and male geese increased 36% and 26%, respectively, above average winter weights. Body weights of paired geese averaged 0.34 kg (females) and 0.27 kg (males) more than those of geese without mates before the weight gain period. Some unmated geese did not gain weight, and others gained less weight than paired geese. Geese shifted from a winter diet of corn (Zea mays) to a diversity of food items in spring. Corn remained the primary source of carbohydrate, and bluegrass (Poa pratensis) provided protein for geese. Weight gain of females was composed of 61% lipid, 10% protein, and 21% water, whereas weight gained by males was 47% lipid, 13% protein, and 35% water. Initial weight gains were predominantly protein (and accompanying water), probably required for gut enlargement. Most of the later body weight gain was due to lipid storage. Increase in size of breast and leg muscles at the end of March was largely due to lipid storage and a shift of protein from other body tissues. Lipid and protein storage was adequate to explain energy and nutrient requirements for body maintenance after arrival on the breeding grounds, egg laying, and territorial defense. Females may have to obtain minerals (and possibly additional protein) for egg formation from food sources on the breeding grounds. Lipid reserves of male Giant Canada Geese indicate an ability to sustain energetic costs during nesting equal to those of the female (apart from egg laying) and are greater than reserves of other species of geese and subspecies of Canada Geese investigated to date.