TRADITIONS OF WATERFOWL 



some great Canadian marshes are already overshot and "burned out." The 

 gunner is moving ever northward. 



Shooting, when it begins before the close of summer, may be respon- 

 sible for the existence of good marshes that lack breeding ducks. Where 

 the young and adult females are killed heavily enough on their native 

 range, local traditions may be broken to the point where, despite plenty of 

 migrants passing through, there are not enough birds with local experience 

 to fill some marshes. Leopol (1931), in his surveys of the North Central 

 states, found that while "only 10 percent of the original marshlands remain 

 in existence, possible only five percent are actually used to any extent." 



During our most recent duck depression, in the middle 1940s, similar 

 vacancies reached deep into Canada. In 1947 Soper (1948:54) found places 

 where "numerous favorable small bodies of water were conspicuously un- 

 derpopulated by waterfowl; and in many tracts, eight or nine sloughs out 

 of every ten, though provided with plenty of water and duck food, had 

 no ducks." In Manitoba's famous Minnedosa pothole region, less than half 

 the water areas had breeding pairs in 1947 (Hawkins, 1948:44). Since the 

 pothole country was not heavily shot (the young and adults most seasons 

 having departed to larger waters before the advent of gunning) the thin 

 nesting populations, as in the case of the shorebirds, may have resulted 

 from overshooting on the flyways. 



An important advantage held by waterfowl over the shorebirds and the 

 Passenger Pigeon is the larger clutch. The Passenger Pigeon laid one, some- 

 times two eggs ( Schorger, 1955 ) , and the standard clutch size in the shore- 

 birds is only four. While there is some variation between species, duck 

 clutches range from eight to twelve eggs, the over-all average being per- 

 haps ten. Thus in successful seasons these waterfowl are able to recover 

 their numbers at a much faster rate than the shorebirds, and the pigeons 

 were at a disadvantage greater still. Moreover, the evidence of Sowls's 

 studies ( 1949 ) is that among the river ducks, at least, there is a persistent 

 drive to renest in the face of early nest loss ; and such renesting may carry 

 the bird to a third attempt after a second catastrophe. The ability to re- 

 cover numbers is shown in the surveys of the Newdale-Erickson district 

 of Manitoba's Minnedosa pothole country, where the breeding population 

 climbed from 26 ducks per square mile in 1947 (Hawkins, 1948) to 81 

 ducks per square mile in 1949 (Hawkins, 1949). By 1953 there were 100 

 ducks per square mile in this district (Kiel, 1953). 



If the number of waterfowl of Minnedosa could be trebled in two years, 



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