Paul A. Johnsgard, Waterfowl, University of Nebraska Press, 1968

SEASONAL SEQUENCE OF EVENTS IN THE YEARLY CYCLE OF THE "GIANT" CANADA GOOSE, BASED ON A COMPOSITE OF DATA FROM THE NORTHERN UNITED STATES AND SOUTHERN CANADA

It is interesting to consider how much time is involved in a successful breeding cycle for waterfowl.

... Furthermore, the large races of Canada Geese have significantly longer incubation and fledgling periods than do the arctic-breeding populations, and require a minimum period of nearly four months to complete their breeding activities (Figure 10).