Fledging Success Survival to fledging of the young in a brood is approxi- 

 mately 75%, or about 5.3 young per brood. The overall annual production is 

 about 1 young bird per adult (Bellrose 1976). 



Age at Fledging Flight is first achieved at 54 to 84 days; Palmer (1976b) 

 believed that most first fly when 60-70 days old. 



Age at First Breeding Most Canvasbacks breed in the first year, except 

 when habitat conditions are adverse (Bellrose 1976). 



Mortality of Eggs and Young Raccoons are major predators of Canvasback 

 nests, particularly with their increasing abundance in the prairie pothole 

 country. Skunks, crows, magpies, and ravens also prey on Canvasback nests. 

 Many female Canvasbacks desert nests because of flooding or intrusion by para- 

 sitic Redheads (Bellrose 1976). 



Renesting There is a considerable amount of renesting by hens that lose 

 clutches, the proportion depending on a variety of extrinsic factors (Bellrose 

 1976). 



Maximum Natural Longevity A bird banded and recovered in New York attain- 

 ed a minimum age of 18 years and 9 months (Clapp et al . in press). 



Weight Bellrose (1976) gave the average weight of 191 males as 2.76 lb 

 (1,250 g) and of 54 adult females as 2.55 lb (1,160 g) . 



SUSCEPTIBILITY TO OIL POLLUTION 



Canvasbacks are known to be victims of oiling. In one month in 1948, an 

 estimated 10,000 wintering ducks (mostly Canvasbacks) died following an oil and 

 yellow phosphorous spill in the lower Detroit River in Michigan (Miller and 

 Whitlock 1948). Most of these ducks froze to death when their natural insula- 

 tion was destroyed by the oil. Eight Canvasbacks were killed by an oil spill 

 in San Francisco Bay, California, in January 1971 (Smail et al. 1972). Mortal- 

 ity following seven oil spills (1973-78) in the Chesapeake Bay and on the lower 

 Delaware River amounted to 815 birds (Perry et al. 1979). Stout and Cornwell 

 (1976) reported that 20% of bands recovered from oiled waterfowl were Canvas- 

 backs, a figure second only to that attained by scaup ( Aythya spp.). 



Most of the Atlantic Canvasback population winters in bays and rivers along 

 the coast north of North Carolina or on large # bodies of water inland. However, 

 the Canvasback is frequently found in large rafts in open water offshore. In 

 such locations an oiling incident could affect many individuals, particularly 

 since one of the two largest concentrations in the southeast is found in Curri- 

 tuck Sound where colder waters would magnify the effects of oiling. In a spe- 

 cies already subject to population fluctuations, accidental oiling could have 

 a significant impact. 



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