( Ensls or Slllqua costata ) , and various yoldias ( Yoldia spp.) are particularly 

 important foods (authors cited iji Bellrose 1976). 



Plant foods eaten include pondweeds (e.g., Potamogeton , Ruppia , Zostera , 

 Zannichellia ) and representatives of a variety of other genera that are listed 

 by Palmer (1976b). 



IMPORTANT BIOLOGICAL PARAMETERS 



Egg Laying Almost nothing is known. Bent (1925) listed egg dates from 

 19 June to 8 July, basing this on twelve records. 



Mean Clutch Size Unknown. Normal clutches are thought to contain 5-9 eggs 

 (Palmer 1976b). 



Incubation Period Unknown (Johnsgard 1975, Palmer 1976b). 



Hatching Success Unknown (Johnsgard 1975, Palmer 1976b). 



Age at Fledging Unknown (Johnsgard 1975, Palmer 1976b). 



Fledging Success Unknown. Murdy (1964 j^n Bellrose 1976) found that twelve 

 pairings produced a total of five broods over a three-year period. 



Age at First Breedin g Unknown. The minimum age at first breeding is sug- 

 gested by Palmer (1976b) to be "presumably two years". 



Mortality of Eggs and Young We have no information, nor do we have any 

 information on whether this species renests. 



Maximum Natural Longevity Unknown. 



Weight Twelve males averaged 2.2 lbs (998 g) , 10 females 2.0 lbs (907 g) 

 (Nelson and Martin 1953). Five summer males from interior Alaska weighed 2.1- 

 2.21 lb (964-1,006 g [mean = 2.17 lb or 987 g)(Irving 1960 in Palmer 1976b). 



SUSCEPTIBILITY TO OIL POLLUTION 



The Surf Scoter is a frequent victim of oiling (Table 9) and was recently 

 rated by King and Sanger (1979) as a species of high concern in this regard in 

 the Pacific Northwest. Palmer (1976b) stated that floating oil is a factor in 

 the mortality of this species along both the Atlantic and Pacific coasts of 

 North America. Many were killed during an early oil pollution incident in San 

 Francisco Bay (Aldrich 1938), and this was one of the four species most adverse- 

 ly affected by the 1971 spill in the same area (Smail et al. 1972). It is of 

 less concern in the waters of the southeastern United States since such a rela- 

 tively small proportion of the total population of the Surf Scoter winters 

 there. We consider it likely that oil spills involving these birds would deci- 

 mate local populations. Areas of maximum concern in southeastern waters would 

 be those farthest north (i.e., the Carolinas) where significant numbers may win- 

 ter. 



373 



