Fledging Success There is about a 23% reduction in brood size through the 

 period of development (Bellrose 1976), but we have no figures for fledging suc- 

 cess as this term is usually applied. 



Age at Fledging Black Ducks become capable of flight at an age of 58-63 

 days (Gollop and Marshall 1954 In Bellrose 1976). Palmer (1976a) reported that 

 young birds usually fly in their 8th week. 



Age at First Breeding Both males and females are capable of breeding in 

 their first year. A large proportion of the females do so, but many males may 

 not breed until the second year or later (Palmer 1976a). In at least one area, 

 about 6-10% of the females did not breed in their first year; these may have 

 been birds that hatched late the preceding summer (Stotts In Bellrose 1976). 



Mortality of Eggs and Young Raccoons are the most important predator on 

 Black Duck nests in the southern portion of the range. In other areas crows 

 and gulls may destroy a large proportion of the nests. Tidal flooding and hu- 

 man activities are other sources of nest failure (Bellrose 1976). As for many 

 other precocial birds, little quantitative information is available on the 

 sources of mortality of Black ducklings, but the factors are probably the same 

 as for other dabbling ducks, i.e., predation and failure to reach water. 



Renesting Renesting is frequent in the Black Duck and in some areas these 

 nesting attempts may account for a large share of the young produced (Bellrose 

 1976). Only rarely is a third clutch initiated after the loss of a second. 

 Various studies have reported a range of 5-26 days between nestings after loss 

 of a clutch. Older hens are more likely to renest than younger ones. In one 

 study, 14% of the yearlings and 49% of older hens renested (various authors 

 cited jji Bellrose 1976). 



Maximum Natural Longevity A banded bird recovered in Delaware had reached 

 an estimated minimum age of 26 years and 5 months (Clapp et al . in press). 



Weight Bellrose (1976) gave the average weights of 346 adult males and 224 

 adult females as about 2.76 lb (1,250 g) and 2.45 lb (1,100 g) , respectively. 



SUSCEPTIBILITY TO OIL POLLUTION 



The Black Duck is a known victim of oiling. In the winter of 1942, oil 

 penetrated inland along coastal New Jersey, killing hundreds of Black Ducks 

 (Peterson 1942). Estimated mortality of Black Ducks killed in seven spills 

 along the Delaware River and in the Chesapeake Bay, 1973-1978 was about 525 

 birds, or about 0.1% of all birds killed (Perry et al. 1979). No other dab- 

 bling duck except the Mallard was as strongly affected. Data from other oil- 

 ing incidents are shown in Table 4. 



A few experimental studies have produced information on the effects of 

 oil on this species. Black Ducks experimentally painted with oil on the breast 

 were shown to ingest significant amounts following preening (Hartung 1963); 

 those experimentally fed cutting or diesel oil developed an inhibition of 

 acetylcholinesterase activity that resulted in incoordination, ataxia, tremors, 



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