inated birds (or both) may not indicate how severely a species was affected. 

 One reason for this is that there is seldom adequate information on the number 

 of birds that were present in an area prior to contamination. As a result, 

 even a relatively accurate estimate of the number of birds killed will not re- 

 veal how badly local populations were damaged. 



Assuming that the number of each species inhabiting an area that becomes 

 oiled was known, it would still be difficult to predict how many birds were or 

 may be affected. For example, the time of passage of an oil slick through an 

 area may be critical in determining the degree of contamination and mortality 

 experienced by each species. During the contamination of the Firth of Forth 

 in February 1978, the oil apparently passed at night near the main feeding area 

 for waterbirds; consequently, there was a proportionately greater loss of night- 

 feeding Greater Scaup and Pochard ( Aythya ferina) than there was of Common Gold- 

 eneye and Common Eider, most of which had moved elsewhere to roost (Campbell et 

 al. 1978). 



The proportion of birds found oiled or dead after a pollution incident may 

 vary widely between species, depending on the habitats used and the habits of 

 the birds. The probability of finding oiled birds that roost or loaf onshore 

 near feeding areas offshore is certainly much greater than it is for those that 

 spend all or most of their time offshore and that, following oiling, might sim- 

 ply sink from sight never to be seen again. 



Furthermore, wind and current patterns offshore as well as movements by 

 the birds themselves could take most of the victims of an oil spill far from 

 where they were oiled long before anyone noticed their plight. Levy (1980) 

 analyzed the sort of oil found on dead or moribund birds in the Atlantic off 

 Canada and suggested that Herring and Great Black-backed gulls obtained near 

 Sable Island, Nova Scotia, had been contaminated by oil from the ARGO MERCHANT 

 spill on Nantucket Shoals, some 840 km (522 mi) away. In another instance a 

 badly oiled Pochard ( Aythya ferina ) flew 7 km (4.3 mi) inland before becoming 

 incapacitated (Campbell et al. 1978). 



In some parts of Europe and on the west coast of the United States prevail- 

 ing winds bring victims of oiling to shore. On the Atlantic seaboard, winds 

 take oiled birds out to sea. It is impossible to make a satisfactory comparison 

 of the extent of damage from oil pollution incidents between these areas. Like- 

 wise, estimates of mortality from beached bird surveys in Europe cannot be used 

 to predict the incidence of mortality along the western coast of the Atlantic. 

 At best, they only suggest that damage to wild birds from oil on the U.S. east 

 coast may be underestimated. 



Despite all these difficulties in obtaining unbiased data, we recommend 

 that a better effort be made to monitor and publish reports of the effects of 

 oil spills on marine birds. Much of the information needed to answer questions 

 relating to oil pollution and marine birds in the southeastern United States 

 that this report attempts to provide would have been available previously had 

 such efforts been made in the past. 



We also recommend that more attention be paid to monitoring the long term 

 and background effects of oil pollution in the southeast. One of the better 



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