per successful nest was about 8.3. Nesting success (i.e., the proportion of 

 nests in which eggs hatch) varies considerably from area to area and from year 

 to year. Studies cited by Palmer (1976b) give a range of 27% to 83%. Palmer 

 (1976b) pointed out that the proportion of eggs hatching in nests in which at 

 least some hatch is high, and cited figures of 83.3% and 91% for two studies 

 conducted in southeastern Alberta. 



Fledging Success Because broods are often combined during development, it 

 is difficult to trace the fate of individual broods and to document fledging. 

 There are indications, however, that post-nesting success is high (Bellrose 

 1976). 



Age at Fledging Young scaup are able to fly at ages of 45-50 days, accord- 

 ing to Bellrose (1976). Palmer (1976b) reported that age of first flight could 

 be estimated as 47-54 days. 



Age at First Breeding Although some Lesser Scaup attempt breeding at one 

 year, most do not do so until two years of age (Trauger 1971, Bellrose 1976). 



Mortality of Eggs and Young Mammals, especially skunks, and birds, espec- 

 ially corvids, are responsible for most nest losses (Bellrose 1976). Nests 

 placed near larid colonies may escape egg predation by crows, but the gulls 

 take large numbers of the young that hatch (Vermeer 1968 in. Bellrose 1976). 



Renesting In an experimental study in which first clutches were removed 

 before incubation began, 5 out of 31 scaup renested once. One renested twice 

 and another three times (Hunt and Anderson 1966). Another study cited by Bell- 

 rose (1976) reported no renesting, yet another assumed that about 39% of the 

 birds renested. 



Maximum Natural Longevity A banded individual reached an age of at least 

 18 years and 4 months (Clapp et al . in press). 



Weight The average weight of 130 males was 1.9 lb (860 g) , and the aver- 

 age of 144 females was 1.7 lb (770 g) (Nelson and Martin 1953). 



SUSCEPTIBILITY TO OIL POLLUTION 



Lesser Scaup are one of the waterfowl that have suffered large losses to 

 oil pollution in North America. It may also be the species of anatid most sus- 

 ceptible to oil pollution in the southeast. More than 2,000 Lesser Scaup were 

 killed by oil during the spring migration of 1963 (Anderson and Warner 1969a, 

 1969b). The sources of the oil were massive spills of crude and soybean oil 

 above the junction of the Minnesota and Mississippi rivers in December 1962 and 

 January 1963 (Peller 1963). At least 1,510 scaup died following five spills on 

 the Delaware River and two on the Chesapeake Bay in the period from 1973 to 

 1978 (Perry et. al. 1979). Most (93.4%) of the scaup mortality occurred in the 

 marine habitat of Chesapeake Bay. Perry et al. (1979) did not report which spe- 

 cies of scaup was involved in this kill. Most, however, were presumably Lesser 

 Scaup because large numbers of this species winter in Chesapeake Bay (Bellrose 

 1976) and because the Greater Scaup is considerably less abundant there. In 



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