the late P. B. Aus, all of FWS, for assistance in the field. 
Others who contributed advice and personal knowledge to 
the study were C. Dixon and D. P. Olson. Suggestions and 
encouragement were contributed by E. F. Bossenmaier, 
H. A. Hochbaum, W. G. Leitch, M. Smith, and the late 
J. D. Smith. 
Assisting with the organizing and editing of earlier drafts 
of this manuscript were J. C. Bartonek, W. R. Goforth, 
H. K. Nelson, P. F. Springer, D. L. Trauger, and the late 
H. W. Murdy. I wish to express my sincere appreciation 
to H. F. Duebbert, R. E. Oetting, and J. R. Serie for their 
dedication to final editing and completion of this publica- 
tion. 
References 
American Ornithologists’ Union, 1957. Check-list of North 
American birds. 5th ed. American Ornithologists’ Union, Bal- 
timore. 691 pp. 
Banfield, A. W. F. 1974. The mammals of Canada. University 
of Toronto Press, Toronto. 438 pp. 
Bartonek, J. C. 1968. Summer foods and feeding habits of diving 
ducks in Manitoba, Ph.D, Thesis. University of Wisconsin, Madi- 
son. 125 pp. 
Bartonek, J. C., and J. J. Hickey. 1969a. Food habits of 
canvasbacks, redheads, and lesser seaup in Manitoba. Condor 
71:280-290. 
Bartonek, J. C., and J. J. Hickey. 1969b. Selective feeding by 
juvenile diving ducks in summer. Auk 86:443-457. 
Bellrose, F. C., T. G. Scott, A. S. Hawkins, and J. B. Low. 1961. 
Sex ratios and age ratios in North American ducks. Ill. Nat. Hist. 
Surv. Bull. 27:391-474. 
Bird, R. D. 1961. Ecology of the aspen parkland of western Canada 
in relation to land use. Can. Dep. Agric. Publ. 1066. 155 pp. 
Cornwell, G. W., and J. C. Bartonek. 1963. Pseudo-sleeping atti- 
tude of the canvasback. Condor 65:444-446. 
Cowan, W. F. 1973. Ecology and life history of the raccoon 
(Procyon lotor hirtus [Nelson and Goldman)]) in the northern 
part of its range. Ph.D. Thesis. University of North Dakota, 
Grand Forks, 161 pp. 
Dzubin, A. 1952. Waterfowl production and behavior study in 
the Minnedosa pothole district of Manitoba. Pages 71-75 in 
Waterfowl populations and breeding conditions— summer 1952, 
U.S. Fish Wildl. Serv., Spec. Sci. Rep. — Wildl. 21. 
Dzubin, A. 1955. Waterfowl! populations and production on the 
Roseneath study area, southern Manitoba. Pages 86-88 in Water- 
fowl populations and breeding conditions — summer 1955. U.S. 
Fish Wildl. Serv., Spec. Sei. Rep. — Wildl. 30. 
Dzubin, A. 1959. Growth and plumage development of wild- 
trapped juvenile canvasbacks (Aythya valisineria). J. Wildl. 
Manage. 23:279-290. 
29 
Ehrlich, W. A., and F. P. LeClaire. 1958, Report of reconnais- 
sance soil survey of West-Lake map sheet area. Manitoba Soil 
Surv., Univ. Manitoba Soils Rep. 8. 
Ehrlich, W. A., E. A. Royser, and L. E. Pratt. 1957. 
Reconnaissance soil survey of Carberry map sheet area. Manitoba 
Soil Surv., Univ. Manitoba Soils Rep. 7. 
Erickson, R. C. 1948. Life history and ecology of the canvasback, 
Nyroca valisineria (Wilson) in south-eastern Oregon. Ph.D. 
Thesis. Iowa State College, Ames. 324 pp. 
Evans, C. D. 1949. Roseneath area brood study, Manitoba, 1949. 
Pages 71-75 in W. F. Crissey. Waterfowl populations and breed- 
ing conditions—summer 1949. U.S. Fish Wildl. Serv., Spec. Sci. 
Rep. — Wildl. 2. 
Evans, C. D., A. S. Hawkins, and W. H. Marshall. 1952. Move- 
ments of waterfowl! broods in Manitoba. U.S. Fish Wildl. Serv., 
Spec. Sci. Rep. — Wildl. 16. 
Geis, A. D., and W. F. Crissey. 1969. Effect of restrictive hunt- 
ing regulations on canvasback and redhead harvest rates and 
survival. J. Wildl. Manage. 33:860-866. 
Hochbaum, H. A. 1944. The canvasback on a prairie marsh. 
American Wildlife Institute, Washington, D.C. 201 pp. 
Kiel, W. H., Jr., A. S. Hawkins, and N. G. Perret. 1972, Water- 
fowl habitat trends in the aspen parkland of Manitoba. Can. 
Wildl. Serv. Rep. Ser. 18. 63 pp. 
Lynch, G, M. 1971. Raccoons increasing in Manitoba. J. Mammal. 
52: 621-622. 
Olson, D. P, 1964. A study of canvasback and redhead breeding 
populations, nesting habitats and productivity. Ph.D. Thesis. 
University of Minnesota, St. Paul. 100 pp. 
Scoggan, H. J. 1978. Flora of Canada. Natl. Mus. Nat. Sci. 
(Ottawa) Publ. Bot. 7:1-1711. 
Shaw. S. P., and C. G. Fredine. 1956. Wetlands of the United 
States. U.S. Fish Wildl. Serv., Cire. 39. 67 pp. 
Smith, A. G. 1971. Ecological factors affecting waterfowl produc- 
tion in the Alberta parklands. U.S. Fish Wildl. Serv., Resour. 
Publ. 98. 49 pp. 
Stewart, R. E, 1971. Check list of birds in North Dakota. Prairie 
Nat. 3:3-12. 
Stewart, R. E., A. D. Geis, and C. D. Evans. 1958, Distribution 
of populations and hunting kill of the canvasback. J. Wildl. 
Manage. 22:333-370. 
Stoudt, J. H. 1959. Redvers waterfowl study area with compara- 
tive data for seven previous years. U.S. Bureau of Sport Fish- 
eries and Wildlife, Wildlife Research Laboratory, Denver. 
110 pp. 
Stoudt, J. H. 1971. Ecological factors affecting waterfowl produc- 
tion in the Saskatchewan Parklands. U.S. Fish Wildl. Serv., 
Resour. Publ. 99. 58 pp. 
Trauger, D, L., and J. H. Stoudt. 1974, Looking out for the can- 
vasback, Part II, Ducks Unlimited 38:30-60. 
Weller, M. W. 1959. Parasitic egg laying in the redhead (Aythya 
americana) and other North American Anatidae. Ecol. Monogr. 
29:333-365. 
Westerskov, K. 1950. Methods for determining the age of game 
bird eggs. J. Wildl. Manage. 14:56-67. 
