An experiment was undertaken to measure food consumption, exereta, and growth of the blaek duek (Anas rubripes) and the Ameriean coot (Fulica americana) under laboratory eonditions. Gross of the food and of the exereta samples was determined with a bomb ealorimeter. The results were used to ealeulate the per g of food. The total amount of retained by the dueks during the 8 weeks was 9,322 keal per bird. The eoots retained S,362 keal per bird or 57 pereent of the retained by the dueks. Brood size was not as mueh a determining faetor of growth rate and eonsumption in coots as it was in dueks. ENERGY REQUIREMENTS OF YOUNG BLACK DUCKS AND COOTS * Penney and Batley 105 Dept. of Interior, Bur. Sport Fish. and Wildl., J. P. Linduska (Editor). 770pp. SMITH:, A. G. 19S8. A progress report on the 1958 waterfowl surveys on the Lousana study area, Lousana, Alberta, Canada. U. S. Bur. Sport Fisheries and Wildl., Wildl. Research Lab., Denver, Colo. 12pp. SOWLS, L. K. 1955. Prairie ducks: a study of their behavior, ecology, and management. The Wildlife Management Institute, Washington, D. C. 193pp. STOUDT, J. H. 1959. Progress report: Redvers waterfowl study area with comparative data for several previous years. U. S. Bur. Sport Fisheries and Wildl., Wildl. Research Lab., Denver, Colo. 1 lOpp. WELLER, M. W., AND P. WARD. l9S9. Migration and mortality of hand-reared redheads ( Aythya americans ) . J. Wildl. Mgmt. 23(4): 427-433. Received for publicstion July 14, 1969. Using Armsby's method, Kendeigh (1949) measured the absorbed by the English sparrow (Passer domestious) throughout a range of temperatures and analyzed the resources of the birds during the year. More recently Stiven ( 1961 ) measured the food required by the blue grouse (Dendlragapus obscurus) chick. He determined total by multiplying the digestible portion of each nutrient for plant and animal foods by factors of 4, 9, or 4 (protein, fat, or carbohydrates respectively) to compensate for losses in the urine. The result was the amount of food available to the animal for combustion or for body tissue. Until recently, little research has been done in the field of flow systems involving populations of wild ducks. Sincock ( 1962) proposed a method to estimate total food demands of a wintering waterINTRODUCTION Most experimentation with requirements of birds has been concentrated on domestic chickens under laboratory conditions. The results of these studies are expressed either in values ( Armsby 1922 ) or in productive values (Hill and Dansky l954). The term metabolizable energy was introduced by Armsby (l922) and defined as the maximum quantity of a feed could contribute to the chemical transformations within an organism. Metabolizable was chosen for this experiment because it is a more easily determined value than productive and is a more accurate criterion of potential for a species than digestive energy. 1 Present address: Box 1012, Sioux Lookout, Ontario. This content downloaded from 157.55.39.104 on Thu, 01 Dec 2016 05:55:15 UTC All use subject to http://about.jstor.org/terms 106 Journal of Wildlife Manugement, Vol. 34, No. 1, January 1970 fowl population in Virginia, using the average body weight of each species. Sugden (1965) compared types of food ingested and food requirements of four species of ducklings, using the plant and animal foods found at the sites where ducklings were collected. There have been no studies conducted on available requirements using wild ducks under laboratory conditions. This study was designed to: (1) measure and compare the requirements of two species of water birds from hatching until flight ( black ducks and American coots represented both dabbling and diving types of marsh birds ); ( 2 ) determine differences between the consumption by the two species and reasons for such differences; ( 3 ) determine the effect of brood size on consumption and growth rate. H. A. Hochbaum, Director, Delta Waterfowl Research Station, supplied the American coot eggs used in this project. W. Carrick, Manager, Kortright Waterfowl Research Station, Guelph, Ontario, supported the work with assistance, helpful suggestions, anfd use of research facilities at the Station.