water across the intestinal wall (Crocker et al. 

 1974). Ingested oil may also affect reproductive 

 success. Grau et al. (1977) showed that ingested 

 oil altered the yolk structure of recently laid 

 Japanese Quail eggs (Coturnix coturnix) and 

 greatly reduced their hatchability. These authors 

 are continuing their studies on the Farallon 

 Islands with Western Gulls and Cassin's Auklets 

 (Ainley et al. 1979). Hartung (1965) demon- 

 strated that ingested lubricating oil reduces the 

 egg laying rate of captive Mallards (Anas 

 platyrhynchos). Oil applied to the exterior of 

 eggs also reduces hatching success. This has been 

 observed in experiments performed on the eggs of 

 Mallards (Hartung 1965), Common Eiders 

 (Somateria mollissima, Albers and Szaro 1978), 

 Laughing Gulls (Lams atricilla, King and Lefever 

 1979), Glaucous-winged Gulls (Larus glaucescens, 

 Patten and Patten 1977), and Great Black-backed 

 Gulls (Larus marinus, Coon et al. 1979, McGill 

 and Richmond 1979). 



The species vulnerable to oil spills are those 

 which are most restricted to an aquatic environ- 

 ment, particularly loons, grebes, seaducks, and 

 alcids, although some variation will occur depend- 

 ing on the season. We have discussed these 

 aspects of each species 1 life history in the species 

 accounts. 



In California, three well-documented oil 

 spills which killed large numbers of birds have 

 occurred: the Santa Barbara oil spill of 1969 

 (Straughan 1971) and the San Francisco oil spills 

 of 1937 and 1971 (Aldrich 1938, Moffitt and 

 Orr 1938, Smail et al. 1972). All three spills 

 occurred in the winter which greatly influenced 

 the species of birds killed. Wintering Western 

 Grebes (Aechmophorus occidentalis) and loons 

 suffered the greatest mortality in the Santa 

 Barbara oil spill. Western Grebes were similarly 

 affected in the 1971 San Francisco oil spill and 

 to a lesser extent in the 1937 spill. Common 

 Murres and wintering scoters (Melanitta spp.) also 

 experienced heavy mortality from oil in the San 

 Francisco oil spills. Common Murres breed in 

 California and appear in the near-shore zone 

 periodically in the winter. 



CHRONIC POLLUTION AND TOXIC 

 CHEMICALS 



Large oil spills are well publicized, but 

 low-level chronic oil pollution, small oil spills, and 

 the build-up of other pollutants probably pose a 

 more serious long-term threat to seabirds. Pollu- 

 tants of particular concern, other than oil, include 



pesticides and their residues, heavy metals, 

 polychlorinated biphenyls and other by-products 

 of industry, and plastic particles. 



Most seabirds are long-lived and feed at or 

 near the tops of their food chains. Certain pollu- 

 tants such as DDT and its principal metabolite 

 DDE are stored in the body and concentrate in 

 increasing amounts at each higher level in the 

 food chain. When concentrations of these chem- 

 icals reach sufficiently high levels, reproduction 

 may be impaired or death may occur. Seabirds 

 constitute one of the most conspicuous and easily 

 studied components of the marine ecosystem, so 

 their reproductive failure or death may be our 

 first indication that the environment contains 

 dangerous quantities of toxic chemicals. In 

 Minamata, Japan, high levels of mercury in 

 effluent from a vinyl chloride plant were first 

 manifested in the deaths of fish-eating birds. This 

 was followed by the tragic deaths of many 

 humans (Kurland et al. 1960). The effects of 

 pollutants on seabirds can be monitored by close 

 study and may serve as a valuable indicator of the 

 health of marine ecosystems. For this reason 

 alone, continued study of certain seabird popula- 

 tions will be useful. 



The effects of chlorinated hydrocarbon 

 pesticides and their residues and polychlorinated 

 biphenyls on birds are well documented (Peakall 

 1970, 1975). These contaminants reduce breeding 

 success by decreasing fertility, reducing the 

 viability of eggs and chicks, and interfering with 

 calcium deposition, resulting in the production 

 of thin eggshells which may later break. Physical 

 abnormalities have also been associated with 

 organochlorine residues (Hays and Riseborough 

 1972). 



In California the Brown Pelican has become a 

 symbol in the fight against pollution of the world's 

 oceans. The reproductive success of Brown 

 Pelicans was seriously reduced by the presence of 

 DDT, DDE, and related chemicals in the ocean 

 off southern California. Because of eggshell 

 thinning, most eggs were broken before the young 

 hatched and only 12 chicks fledged out of 2,368 

 nesting attempts in 1969, 1970, and 1971 (Gress 

 et al. 1973). Double-crested Cormorants suffered 

 a similar decrease in reproductive success in 

 southern California and Mexico (Gress et al. 

 1973). These reproductive failures were traced to 

 DDT dumped into the Los Angeles sewer system 

 by a chemical manufacturing plant. Since April, 

 1970, these wastes have been deposited in a 

 landfill and DDT input into the ocean has declined 

 significantly (Anderson et al. 1975). Reproductive 



