gulls) predators account for a large proportion of destroyed nests, and many 

 others are flooded by sudden increases in water level. Nests may also be de- 

 serted in time of drought or low water (Bellrose 1976). 



Renesting Alliston (1979b) first documented renesting in Redheads. He 

 found that 86.4% of 22 females whose clutches were removed later renested. 

 Clutch size in first nests averaged 10.5 (n =8), versus 10.3 for second nests, 

 a statistically insignificant difference. 



Maximum Natural Longevity A bird banded in Maryland after its second year 

 was recovered in Michigan at a minimum age of 21 years and 5 months (Clapp et 

 al . in press) . 



Weight Males (n = 1,157) in spring migration averaged 1,100 g (2.43 lb) 

 and females (n = 485) averaged 990 g (2.18 lb). Thirty-two summer males aver- 

 aged 940 g (2.07 lb) and 71 females averaged 900 g (1.98 lb). During fall mi- 

 gration, 40 males had a mean weight of 990 g (2.18 lb) and 52 females averaged 

 900 g (1.98 lb) (Weller 1957 in Palmer 1976b). 



SUSCEPTIBILITY TO OIL POLLUTION 



At least five Redheads were included among more than 8,400 birds killed by 

 an oil spill in Chesapeake Bay (Roland et al. 1977). A very large proportion 

 of the entire species population winters in the southeast, often in large aggre- 

 gations in habitats susceptible to oiling. This duck also belongs to a group 

 of diving ducks ( Aythya ) whose feeding habits make thera especially vulnerable 

 to the effects of oil. Consequently, we regard this species as one potentially 

 at high risk from oil pollution in the southeast. 



BIBLIOGRAPHY 



1981 



Cable, T. T. 1981. Nest of Redhead Duck in Newton Co.: first state nesting 

 record. Indiana Audubon Q. 59: 4-5. 



Sugden, L. A. 1981. Parasitism of Canvasback nests by Redheads. J. Field 

 Ornithol. 51: 361-364. 



1980 



Bauer, C.-A., S. Christiansson and G. Rudebeck. 1980. Amerikansk brunand , 



Aythya americana , en ny art for Euro pa , funnen i Malmo. [Redhead, Aythya 

 americana , a species new to Europe, found in Malmo, Sweden.] Var Fagel- 

 varld 39: 275-276. 



Nudds, T. D. 1980. Canvasback tolerance of Redhead parasitism: an observation 

 and an hypothesis. Wilson Bull. 92: 414. 



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