338 



of recovery. Birds under stress are also probably more vulnerable to predation 

 than healthy birds. 



Some waterbirds that become contaminated with nonlethal do.ses of petroleum 

 during the breeding season are not likely to contribute to the annual pro<luction. 

 Hartung (1965) found that ducks which had been fed small doses of a relatively 

 non-toxic, lubricant oil stopped laying for about two weeks, wl)ile '"control" ducks 

 continued to lay normally. Many shorebirds which rely upon the intertidal zones 

 for feeding may find tliem completely blanketed with oil." 



Other ramifications of oil in the avian marine habitat are discussed in tlie 

 preceding section on "Marine Fishery Resources". 



NATUBE OF CONTAMINATION 



Groups believed to be the most susceptible to contamination by oil along the 

 marine route between Valdez and southern ports are : murres, guillemots, auklets, 

 murrelets, puflSns, cormorants, loons, grebes, eiders, scoters and oldsquaws. Sheer- 

 waters, fulmars, albatros. petrels, gulls, tern.s, shorebirds and some ducks 

 and geese are also vulnerable to contamination at sea but less so than divers. 



Some bird species are more vulnerable to oil than others as indicated by 

 records of casualties (Clark and Kennedy, 1968; Bourne, 1968b; Wallace, 1971) 

 which show good relationships between the amount of time that a species spends 

 in the water and the frequency of contamination (Erickson, 1963). In Great 

 Britain (Bourne and Devlin, 1969) oil has had its main impact on a limited 

 number of diving birds \thich are already known to be decreasing, including, 

 especially the auks and common scoter. Although a considerable number of 

 gulls are affected, their mortality rate appears to be much lower, presumably 

 because they seldom become as soaked with oil as alcids and because they do 

 not stay on the water to get chilled afterwards. 



Bourne and Devlin (1969) believe that the main mortality from oil pollution 

 arises because birds on the water are trapped unawares by long slicks drifting 

 toward them. Presumably once the birds are caught in the oil they drift \A'ith it 

 until they .starve to death and their botlies either sink or wash ashore days later. 



According to Bourne (1968a), suggestions that birds positively seek out oil 

 because it makes the water calm, or resembles food, or tide-rips, or shoaling 

 fish associated with the presence of food, seem to be based chiefly on .specula- 

 tion. He observed swimming birds not taking notice of a drifting, narrow slick 

 of oil until they came in contact with it. Upon contact, gulls flew away and 

 murres dived beneath the slick. The diving behavior of aicids to escape danger 

 would probably be fatal if they rose from the dive into the slick, such as was 

 believed to have been the case for most alcids killed during the "Torrey Can- 

 yon" disaster. 



Birds that concentrate and feed along current convergence lines may be sus- 

 ceptible to contamination by oil. Evans (1969) found that some spilled oil in 

 Cook Inlet collected within and attached to the windrowed vegetation and 

 debris that occurs along convergence lines ; he believed that that oil would 

 float about on tidal currents for an extended period. 



REFERENCES CITED 



Aldrich, E. C, 1938, A recent oil pollution and its effect on the water birds in 



the San Francisco Bay area : Bird-Lore 40 :110-114. 

 Aldrich, J. W.. 1970, Review of the problem of birds contaminated by oil and 



their rehabilitation: U.S. Dept. Int., Fish and Wildl. Service. Bur. Sport 



Fisheries and Wildl. Resource Publ. 87. 23 pp. 

 APSC, (Alyeska Pipeline Service Con-oany), 1971c. Project description of the 



trans-Alaska pipeline system : Submission to U.S. Dept. of the Int»^rior, 



Aug. 8, 1971, 3 V. plus 26 v. appendices. 

 Anonymous. 1968. Dead ducks again : Alaska Conserv. Rev., 9(3) :6. 

 Barrv. T. W.. 1962. Effect of late seasons on Atlantic brant reproduction: 



J. Wildl. Mgmt. 26(1) :19-26. 

 Beer, J. V., 1968, Post-mortem findings in oiled auks dying during attempted 



rehabilitation, pp. 123-129. In J. D. Carthy and D. R. Arthur (Editors). The 



biological effects of oil pollution on littoral communities : Field Studies. Vol. 2, 



Suppl. 198 pp. 

 Blumer. M., 1969, Oil pollution of the sea, pp. 5-13. In D. P. Hoult. Ed., Oil on 



the Sea : Plenum Press, New York. 114 pp. 

 Bourne, W. R. P.. 1968a. Observation of an encounter between birds and floating 



oil: Nature 219(5154) :632. 



