21 



from Alaska. Significant eggshell thinning 

 has occurred among eggs in samples from 

 most major areas. Some eggs contained DDE 

 residues of the same magnitude as those that 

 produced shell thinning in experimental 

 species. High dieldrin residues in some eggs 

 could have an adverse effect on reproductive 

 success. 



Egg failure was the major cause of poor re- 

 productive success of ospreys on the Potomac 

 River during 1970 (Wiemeyer 1971). Many 

 eggs disappeared between visits to the nests; 

 some were found broken or damaged in the 

 nests, and others failed to hatch. 



Osprey eggs were exchanged between Con- 

 necticut and Maryland nests in 1968 and 1969 

 to determine which environmental factors 

 might have contributed to the decline in re- 

 productive success of Connecticut ospreys 

 (Wiemeyer et al. 1975). Incubation of 30 Con- 

 necticut osprey eggs by Maryland ospreys did 

 not improve the hatching rate. Forty-five 

 Maryland osprey eggs incubated by Connecti- 

 cut ospreys hatched at their normal rate. The 

 results of the egg exchanges and associated 

 observations indicated that the most prob- 

 able cause of the poor reproduction of Connec- 

 ticut ospreys was related to contamination of 

 the birds and their eggs. Residues of DDT and 

 its metabolites, dieldrin, and PCB's were gen- 

 erally higher in fish from Connecticut than 

 from Maryland. There were no major changes 

 in residue content of Connecticut eggs col- 

 lected in 1968-69 compared with those col- 

 lected in 1964. One Connecticut osprey had a 

 concentration of dieldrin in its brain that was 

 in the lethal range. The average shell thick- 

 ness of recently collected osprey eggs from 

 Connecticut had declined 18%, and those 

 from Maryland had declined 10% from pre- 

 1947 norms. Dieldrin, DDE, and PCB's are 

 three environmental pollutants that have 

 most likely been important factors in the 

 greatly reduced reproductive success and 

 rapid population decline of Connecticut 

 ospreys. 



All black duck eggs that were collected in 

 1971 from the northeastern United States and 

 Canada contained DDE residues (Longcore 

 and Mulhern 1973). Means for States and 

 Provinces ranged from 0.09 to 5.94 ppm, with 

 mean concentrations exceeding 1.0 ppm in 

 eggs from Maine, New York, New Jersey, and 

 Delaware. The highest DDE concentration 

 (14.0 ppm) was in an egg from Delaware. The 



ODD and DDT residues averaged <0.5 ppm 

 for each collection area. No mirex residues 

 and only trace amounts of dieldrin and hepta- 

 chlor epoxide were detected. Of the 61 eggs, 

 57 contained PCB's; means ranged from 

 < 0.05 ppm in samples from Nova Scotia to 

 3.30 ppm in those from Massachusetts, with 

 trace amounts occurring in nearly half the 

 samples. Mean organochlorine pesticide resi- 

 dues were lower in the 1971 samples than in 

 those analyzed in an earlier study in 1964. 

 Average shell thickness of eggs collected in 

 1964 (0.321 mm) was significantly less 

 (P < 0.01) than that of eggs collected before 

 1940 (0.348 mm) or in 1971 (0.343 mm). 



Eggs of captive black ducks fed diets con- 

 taining DDE at 10 and 30 ppm (dry weight; 

 approximately 3 and 9 ppm wet weight) ex- 

 perienced significant shell thinning and an in- 

 crease in shell cracking when compared with 

 eggs of untreated black ducks (Longcore et al. 

 1971b). Survival of ducklings from dosed 

 parents in terms of "percentage of 21- 

 day ducklings of embryonated eggs" was 40- 

 76% lower than survival of ducklings from un- 

 dosed parents. Average DDE residues in eggs 

 from hens fed 10 and 30 ppm DDE were 

 46 ppm and 144 ppm. 



In another experiment, black duck hens fed 

 10 ppm (dry weight) of DDE in the diet laid 

 eggs with shells 22% thinner at the equator, 

 30% thinner at the cap, and 33% thinner at 

 the apex than those of controls (Longcore and 

 Samson 1973). Natural incubation increased 

 shell cracking more than fourfold as compared 

 with mechanical incubation. Hens removed 

 cracked eggs from nests, and one hen termi- 

 nated incubation. Hens fed DDE produced 

 one-fifth as many ducklings as did the con- 

 trols. The DDE in eggs of dosed hens aver- 

 aged 64.9 ppm. 



Concentrations of 10 and 40 ppm DDE (dry 

 weight) in the feed of penned mallard ducks 

 caused significant eggshell thinning and 

 cracking and a marked increase in embryo 

 mortality (Heath et al. 1969). In other studies, 

 eggshell thinning also occurred in mallards 

 fed DDE (Haegele and Hudson 1974), DDT 

 (Tucker and Haegele 1970; Davison and Sell 

 1974), or dieldrin (Lehner and Egbert 1969; 

 Muller and Lockman 1972; Davison and Sell 

 1974), but low dietary levels (25 and 50 ppm) 

 of Aroclor 1254 produced no measurable re- 

 productive effects (Heath et al. 1972b). 



