Wing surveys of the last 3 years have shown 

 declining age ratios. In 19(10 the immature-to- 

 adult ratio was i* : 1, in 1961 it was 1 : 7, and in 1962 

 it was 1 : 5. .Mortality studies indicate that a 2: 1 

 ratio is barely adequate to rebuild a popu- 

 lation if it is hunted heavily. So far as deter- 

 mined, the breeding-ground habitat has not 

 changed drastically during this period, and cli- 

 matic changes have not been sufficient to explain 

 the reduced breeding success. 



The possible effect of pesticides on black duck 

 populations was considered worthy of exploration. 

 Since black ducks feed on animal life as well as 

 plant material, they may be more susceptible to 

 exposure to pesticides than many other species 

 of waterfowl. During the winter, for example, 

 they often feed avidly on worms, small clams, 

 mussels, snails, small crabs, other crustaceans, and 

 small fish. 



In an exploratory survey, three black duck eggs 

 were collected from each of three to five nest 

 samples in a series of representative breeding 

 areas. Sample clutches were received from Nova 

 Scotia, New Brunswick, Maine, Vermont, Massa- 

 chusetts, Connecticut, New York, New Jersey, 

 Delaware, Maryland, and Michigan. Eggs were 

 opened and examined for freshness and stage of 

 embryonic development, then prepared for chemi- 

 cal analysis of residues. The three eggs from a 

 single nest were pooled for a sample unless they 

 differed in developmental stage or freshness. 



Analyses completed to date bj the thin-layer 

 chromatographic technique showed DDT residues 

 in .'id of 37 clutches taken in 8 States from Maine 

 to Maryland, indicating a high incidence of egg 

 contamination. 



Effcetx of pesticides on osprey productivity. — 

 Ospreys studied by Patuxent have decreased in 

 Atlantic-coast areas for several years, and con- 

 servationists are wondering if pesticides are in- 

 volved in the decline. Since ospreys subsist on 

 shoal-water fish, they could be exposed regularly 

 to toxicants through the food chain. 



The presence of pesticides in osprey eggs and 

 young was shown in 190:2 by Mr. Peter Ames of the 

 Yale Peabodv Museum, who reported DDT oi 

 its metabolites in six eggs, one nestling, and ohm 

 embryo. Three fish samples taken from osprey 

 nests at Old Lyme also contained pesticide residues. 

 The colony is declining, and reproductive success 

 is low. 



A biologist checks on osprey's nest. The never-abundant 

 osprey, a fish-eating hawk, is vulnerable to pesticides of 

 the chlorinated hydrocarbon group which may accumulate 

 in the water where it feeds. (Photo by F. C. Sehniid) 



Parallel studies were accordingly initiated in 

 two areas, Old Lyme and the lower Potomac in 

 Maryland, where an osprey colony apparently was 

 thriving. Single eggs were taken from a series 

 of nests in each locality, and the success of the 

 remaining eggs was followed. Embryo develop- 

 ment in the eggs collected was determined in the 

 laboratory. Pesticide determinations for the eggs 

 have not yet been completed. Food samples and 

 a series of fecal samples from the nest sites were 

 collected for analysis if pesticide residues in the 

 eggs indicate that this is desirable. 



A comparison of nest histories from which eggs 

 were taken showed that the lower Potomac nestings 

 were more successful. Here, eggs from 17 of 26 

 nests hatched 27 nestlings and fledged 24 young. 

 Eleven eggs disappeared from nests, and ?> failing 



49 



