sociated with oil pollution (Tuck 1960), al- 

 though the effects probably are not related 

 only to those caused by feather-oiling. Numer- 

 ous other instances of mortality related to oil 

 are documented in reviews on this subject 

 (Clark and Kennedy 1968; Aldrich 1970; Ver- 

 meer and Vermeer 1974a). 



The effects of oiled plumage on marine birds 

 vary with the properties of the oil, degree of 

 contamination, quantity absorbed, environ- 

 mental conditions, and the original condition 

 of the bird. Even a small patch of oil on the 

 feathers may mean that without care the bird 

 will die (Tuck 1960; Smith 1975), but in some 

 instances it appears that birds are able to 

 clean their own plumage (Phillips 1974; Smith 

 1975). Oiling of a bird's plumage increases me- 

 tabolism and causes an increased loss of body 

 heat to the surrounding cold water that can 

 readily be fatal (Lincoln 1936; Hartung 1967; 

 Boyle 1969; Greenwood 1970; McEwan and 

 Koelink 1973). 



Feather-oiling appears to be a more signifi- 

 cant problem in cold-water areas than in areas 

 where water is warmer. Warm water appar- 

 ently causes the spilled liquid oil to form tar- 

 balls that are comparatively less hazardous to 

 birds (Bourne and Bibby 1975). 



Damage to feathers may result long after 

 exposure and may be reflected by abnormal 

 wear of the plumage (Bourne 1974). 



After the Torrey Canyon grounding in 

 March 1967, 7,849 oiled birds were captured 

 for cleaning and rehabilitation. One month 

 later, however, fewer than 6% were still alive 

 (Clark and Kennedy 1971). 



An estimated 3,180,000 liters of bunker C 

 fuel oil were spilled in the massive 1971 oil 

 spill that occurred near the entrance to San 

 Francisco Bay. The California Department of 

 Fish and Game estimated that 7,000 aquatic 

 birds were exposed to the fuel oil, and more 

 than 4,000 of these were taken into captivity 

 for treatment and rehabilitation. Two weeks 

 after the spill, 90% of the birds had died in 

 spite of efforts to save them, and within 3 

 months mortality exceeded 96% (Orr 1971; 

 Snyder et al. 1973). Grebes, murres, and loons 

 apparently died more rapidly than the other 

 species affected, and ducks appeared most 

 hardy (Snyder et al. 1973). 



Progress has since been made in the reha- 

 bilitation of oiled birds, and modified methods 

 are being used (Hay 1975). In 1973, the Inter- 



national Bird Rescue Research Center treated 

 523 oiled birds of which 49% survived (Smith 

 1975). 



Toxicology, Physiology, and Pathology 



The great diversity of chemical compounds 

 in oil increases the difficulty of determining 

 its toxicological and physiological effects. In 

 addition, oil dispersants used to clean up a 

 spill area are also toxic and the toxicity of oil 

 plus dispersant usually is greater than the 

 toxicity of either alone (Clark and Kennedy 

 1968; Tarzwell 1970; Linden 1975). There also 

 are important species differences in suscep- 

 tibility (Swedmark et al. 1973). 



The toxicity of some oils to ducks has been 

 measured under different environmental con- 

 ditions. Single doses of several industrial oils 

 produced lipid pneumonia, gastrointestinal ir- 

 ritation, fatty livers, and adrenal cortical 

 hyperplasia. Birds that received a cutting oil 

 in combination with diesel oil exhibited acinar 

 atrophy of the pancreas. Those that received 

 diesel oil and a fuel oil developed toxic nephro- 

 sis. Cholinesterase activity was significantly 

 inhibited by administration of the cutting oil 

 and somewhat depressed by the diesel oil 

 (Hartung and Hunt 1966). 



Ducks that had been killed by oil pollution 

 exhibited changes that were similar to those 

 in the experimentally fed birds, suggesting 

 that toxicity of oils is a major factor in mor- 

 tality of exposed birds (Hartung and Hunt 

 1966). Toxicity apparently is reduced through 

 aging of the oil because the more volatile com- 

 pounds are also the more toxic (Clark and 

 Kennedy 1968). 



Birds that died after the San Francisco Bay 

 oil spill in 1971 were examined for pathologi- 

 cal changes that might have resulted from ex- 

 posure to oil. Intoxication from oil ingestion 

 appeared to be an important factor contribut- 

 ing to the high mortality, although the evi- 

 dence was circumstantial. Birds that died in 

 the period of high mortality had ingested oil 

 and exhibited dehydration, ulceration of the 

 intestinal mucosa, enteritis, hepatic fatty 

 changes, and renal tubular nephrosis (Snyder 

 et al. 1973). Similar pathological changes as 

 well as adrenal lesions and pulmonary dis- 

 eases have been observed in other oiled sea- 

 birds (Guillen 1967; Beer 1968). 



Following the large 1974 oil spill in the 



