Mississippi Christmas (1960) reported Greater Scaup feeding on dis- 

 carded, dead Gulf menhaden ( Brevoortia patronus ) on a small bayou near Davis 

 Bay. 



IMPORTANT BIOLOGICAL PARAMETERS 



Egg Laying Nests are begun in June, mainly in mid-June, according to 

 studies cited by Bellrose (1976) and Cramp et al. (1977). 



Mean Clutch Size Clutches on islands in Great Slave Lake, Northwest Ter- 

 ritories, consisted of 4-21 eggs, although the larger ones contained eggs de- 

 posited parasitically by other species. The average clutch was 9.0, or 8.5 

 with the parasitized nests omitted from the calculations (Trauger and Bromley 

 1975 in Bellrose 1976). Palmer (1976b) stated that the clutch size is commonly 

 7-9 eggs. The modal clutch size for first clutches in Finland was 11; the mean 

 for first clutches in Iceland was 9.7 (authors cited i^ Cramp et al. 1977). 



Incubation Period Palmer (1976b) found no data on the incubation period 

 for North American birds but cited a study (Hilden 1964) that reported 24-25 

 days for Greater Scaup in Finland. 



Hatching Success Few data are available. In two studies cited by Bellrose 

 (1976), 25-45% of the nests observed were successful, but the number of birds 

 hatched in these nests was not given. Cramp et al. (1977) listed hatching suc- 

 cess rates of 77% for Finnish birds and 67.9% for Icelandic birds; the range for 

 the latter over a period of ten years was 47.6% to 84.3%. 



Fledging Success Few data are available. Bellrose (1976) believed that 

 mortality of ducklings was low. In Finland only 6.5% of the eggs laid resulted 

 in birds raised to fledging (Hilden 1964 .in Cramp et al. 1977). 



Age at Fledging Data are not available for North American birds. Cramp 

 et al. (1977) reported a fledging period of 40-45 days. 



Age at First Breeding There is evidence that most females do not nest un- 

 til their second year or later (Trauger i_n Bellrose 1976), but some yearling 

 females breed; other data indicate that some yearling males also breed (Palmer 

 1976b). 



Mortality of Eggs and Young Most of the relatively few eggs that did not 

 hatch during a study conducted in Finland (Hilden 1964 jji Johnsgard 1975) were 

 lost to crows and ravens; a few eggs were also lost to floods. Sources of mor- 

 tality for New World Greater Scaup are virtually unknown, but Bellrose (1976) 

 believed that mortality was slight among unfledged ducklings. 



Renesting We have found no information on renesting by North American 

 Greater Scaup. Bengtson (1972a in Cramp et al. 1977) reported that 31% of 45 

 Icelandic females re-laid after loss of the first clutch. The mean clutch size 

 for second clutches was 7.0. 



Maximum Natural Longevity Banding records in the United States indicated 



296 



