fects of oil on marine birds are little known. 

 Important biological effects include both 

 acute and chronic toxicity as well as adverse 

 effects on physiology, reproduction, and be- 

 havior. Indirect effects involving the food web 

 and changes in habitat and food supply are 

 relatively unknown. 



There is a distinct possibility that oil and 

 other environmental contaminants such as 

 the organochlorine compounds may act syner- 

 gistically (Farrington 1977). 



Circumstantial evidence suggests that oil 

 pollution has seriously reduced populations of 

 certain species of marine birds in some areas 

 (Tuck and Livingston 1959; Tuck 1960; 

 Hawkes 1961; Buck and Harrison 1967; Par- 

 slow 1967, 1970; Bourne 1968; Clark 1973). 



An oil spill can have significant effects on 

 populations of marine birds such as the alcids, 

 which often are numerous among the birds 

 that die in spills. Although alcids are long- 

 lived and have few predators once they are at 

 sea, they often do not breed until 3 or more 

 years old, most lay only a single egg per 

 clutch, not all adults breed every year, and 

 they produce an average of only one chick per 

 five breeding adults. These species require 

 more than 50 years to double their population 

 under optimal conditions. More than half a 

 century would be required for a colony to re- 

 cover its numbers (excluding immigration) if 

 reduced by one-half as the result of a large oil 

 spill (Clark 1969). 



The potential effects of oil spills on aquatic 

 birds and their feeding habitat on the Cana- 

 dian west coast were assessed by Vermeer and 

 Vermeer (1975). They concluded that the pres- 

 ent shipping of oil plus the increased tanker 

 traffic along the entire British Columbia coast 

 that is expected to be in progress in 1977 will 

 result in enough oil spillage to threaten the 

 coastal populations of seabirds with destruc- 

 tion. 



Concentrations of seabirds will be most vul- 

 nerable to spills (Vermeer and Vermeer 1975). 

 Three major colonies along the coast of 

 British Columbia are the Langara Region, the 

 southeast coast of the Queen Charlotte 

 Islands, and the Scott Islands. Alcids and 

 storm petrels (Oceanodroma spp.) are the 

 most numerous seabirds along the British 

 Columbia coast. Alcids are among the birds 

 most vulnerable to oil pollution, whereas 

 storm petrels are less threatened by spills be- 



cause they spend more time in the air and dive 

 only occasionally. Waterfowl, especially div- 

 ing ducks, will be vulnerable to spills during 

 the winter as they concentrate in large 

 numbers in estuaries and inlets along the 

 British Columbia coast. The large wintering 

 populations of ducks, geese, and grebes along 

 the Eraser Delta foreshore and Boundary 

 Bay will be vulnerable because of their near- 

 ness to tanker and shipping traffic. Approxi- 

 mately 1 million loons, shearwaters, phal- 

 aropes, ducks, gulls, and geese migrate north 

 in the spring along west Vancouver Island. 

 These migrants, because of their concentra- 

 tion in large numbers, may be very tempo- 

 rarily but critically vulnerable to oil pollution. 

 The birds most likely to be directly affected 

 by spills are breeding populations of alcids 

 and wintering diving ducks, whereas ducks, 

 geese, and shorebirds, which feed in the inter- 

 tidal zone, may be hardest hit indirectly 

 through destruction of their feeding habitat 

 (Vermeer and Vermeer 1975). Of the ducks 

 threatened by destruction of their feeding 

 habitat, sea ducks are most vulnerable be- 

 cause they rely most on the marine habitat for 

 feeding purposes. 



Feather-oiling 



Large numbers of marine birds die each 

 year as a result of oil spills. Estimates of mor- 

 tality are based primarily on beach counts of 

 oiled birds, but such estimates may be highly 

 inaccurate because a significant percentage, 

 perhaps 50-90%, of the dead birds never wash 

 ashore (Clark and Kennedy 1968; Coulson et 

 al. 1968; Tanis and Morzer Bruyns 1968; 

 Hope-Jones et al. 1970). 



An estimated 30,000 marine birds, of which 

 about 97% were common murres and razor- 

 bills (Alca torda), died as a result of the Torrey 

 Canyon disaster (Bourne et al. 1967). Earlier, 

 in the winter of 1951-52, approximately 

 100,000 birds were lost to oil pollution on the 

 coasts of the British Isles (ZoBell 1962). At 

 least 10,000 birds, including alcids, ducks, 

 gulls, and kittiwakes, were killed by oil appar- 

 ently derived from ballast pumped from 

 tankers entering Cook Inlet, Alaska, during 

 February and March 1970 (U.S. Department 

 of the Interior 1970). 



The population decline of murres (Uria spp.) 

 along the coast of Newfoundland has been as- 



