may die or suffer physiological or behavioral changes, including reproductive 

 failure (Crocker et al. 1974 and 1975; Grau et al. 1977; Miller et al. 1977; 

 Szaro et al. 1978a; and Wooton et al. 1979). Birds may also ingest petroleum 

 products contained in tissues of fish or marine invertebrates. 



Nesting birds can transfer oil from their feathers or feet to eggs while 

 incubating. Small amounts of oil (equal to a few drops) can kill embryos 

 inside the eggs (Albers 1977; Szaro and Albers 1977; Albers and Szaro 1978; 

 Szaro et al. 1978b; and others). Bird embroys are most sensitive during the 

 first 10 days of incubation. 



Oil spills also damage marine and intertidal environments where waterbirds 

 feed, nest, and roost. Birds often abandon areas after an oil spill because 

 habitat quality is poor and prey populations are reduced (Buck and Harrison 

 1967; Abraham 1975; and Hope Jones et al. 1978). Recovery can take as long 

 as 10 years. 



Among the waterbird groups, seabirds are probably most vulnerable to oil 

 spills because they have a greater chance of coming in contact with oil. 

 Seabirds that spend most of the time on the water, such as eiders, cormorants, 

 alcids, loons, and grebes, are more susceptible to feather-oiling than species 

 that feed on the wing (such as petrels, terns, and, to a lesser extent, 

 gulls). All species of seabirds that breed along the coast of Maine could 

 suffer reduced reproductive success from egg-oiling if a spill occurred during 

 the nesting season (April to June) . 



Shorebirds would be most vulnerable to spills during migration, particularly 

 if spills occurred or washed ashore at night when large numbers of birds are 

 concentrated on roosts near the waters edge. Wading birds are less 

 susceptible to feather oiling than other waterbirds because they have long 

 legs and their feathers do not always come in contact with the water, but oil 

 could be transferred from their feet to eggs. 



Toxic chemicals . The most important toxic chemicals in marine and 

 estuarine systems are the chlorinated hydrocarbons, DDT and its metabolites 

 DDD and DDE, and polychlorinated biphenyls (PCBs). Use of DDT has been banned 

 in the U.S., so little or no DDT, DDD, or DDE currently enter Maine waters. 

 Migratory birds may be exposed to these chemicals in wintering areas outside 

 the U.S. PCBs are used primarily for industrial products, such as heat 

 exchangers and condensors (Ohlendorf et al. 1978a). Large quantities of PCBs 

 enter the marine system primarily in industrial waste, sewage sludge, and when 

 plastics are burned and transported in the atmosphere. These chemicals occur 

 in concentrations around industralized areas (Howe et al. 1978). 



Chlorinated hydrocarbons are chemically stable, relatively insoluble in water, 

 and may remain in the ecosystem for long periods of time. They can accumulate 

 in the fat of organisms and concentrations can magnify as they pass from prey 

 to predator along the food chain. Very little is lost by way of excretion. 

 Concentrations are highest in species of birds such as eagles, ospreys, 

 herons, and terns, that feed on fish. For this reason fish-eating species 

 make good indicators of the abundance of hydrocarbons. 



Chlorinated hydrocarbons may affect birds directly by killing them or by 

 interfering with their reproductive processes (i.e., eggshell thickness) and 



14-43 



10-80 



