Straits of Magellan, a high percentage of 

 South American tern (Sterna hirundinacea) 

 chicks on an island in the spill area died 

 (Smithsonian Institution 1974). Although the 

 cause of mortality is unknown, it is possible 

 that the small fish that the terns ate and fed 

 to their young were contaminated with some 

 fraction of the spilled crude oil in concentra- 

 tions that did not harm the adults but were 

 toxic to the young. It is possible, however, 

 that the chicks died of starvation after the 

 adults were killed or were unable to catch 

 enough food for the young. 



The rates at which water and sodium are 

 transported across the intestinal mucosa in- 

 crease when Pekin ducklings (Anas platyrhyn- 

 chos) are transferred from fresh water to a 

 diet containing hypertonic saline drinking 

 water (Crocker et al. 1974). These rate in- 

 creases seem to be essential for the successful 

 adaptation of ducklings to saline drinking 

 water. Ducklings given a single oral dose of a 

 crude oil (0.2 ml) at the start of maintenance 

 on saline drinking water did not develop the 

 characteristic rate increases. In addition, high 

 mucosal transfer rates that had been de- 

 veloped in ducklings fed saline water for 

 3 days ceased 24 h after they received crude 

 oil. Although commercial dispersant (5 ppm 

 or 20 ppm) in fresh or saline drinking water 

 had no effect on ducklings, the presence of dis- 

 persed crude oil (12.5-50.0 ppm) in the water 

 prevented the development of high mucosal 

 transfer rates in the ducklings given saline 

 water. 



A reduction of the mucosal transfer rates in 

 seawater-adapted ducklings, through the 

 action of ingested crude oil, may limit the 

 amount of free water available to the body 

 (Crocker et al. 1974). Although the high mor- 

 tality among oil-contaminated seabirds may 

 be due to a variety of pathological conditions, 

 dehydration resulting from impairment of 

 mucosal transfer mechanisms may be an im- 

 portant factor contributing to their death. 



Crude oils from eight different geographical 

 locations reduced the rates of sodium and 

 water transfer across the intestinal mucosa of 

 Pekin ducklings to different degrees (Crocker 

 et al. 1975). Administration of Kuwait crude 

 oil caused the greatest degree of inhibition, 

 and North Slope, Alaska, crude oil caused the 

 smallest. 



Distillation fractions derived from two 

 chemically different crude oils were adminis- 



tered to ducklings in volumes that corre- 

 sponded to their relative abundance in the 

 crude oil from which they were derived 

 (Crocker et al. 1975). The greatest inhibitory 

 effect on mucosal transfer was not associated 

 with the same distillation fractions from each 

 oil. A highly naphthenic crude oil from the 

 San Joaquin Valley, California, showed the 

 greatest inhibitory activity in the least abun- 

 dant (2%), low boiling point ( < 245 C) fraction. 

 The most abundant (47%), highest boiling 

 point (>482 C) fraction showed the least in- 

 hibitory activity. In contrast, a highly paraf- 

 finic crude oil from Paradox Basin, Utah, 

 showed the greatest inhibitory effect with the 

 highest boiling point fraction and a minimal 

 effect with the lowest boiling point fraction. 

 The relative abundances of these two frac- 

 tions in the Paradox Basin crude oil repre- 

 sented 27 and 28%. 



Mucosal transfer inhibition by water-sol- 

 uble extracts of San Joaquin Valley and Para- 

 dox Basin crude oils was roughly proportional 

 to the inhibitory potency of the low boiling 

 point fraction of the oil (Crocker et al. 1975). 

 Weathered samples of these oils showed 

 greater effects than corresponding samples of 

 unweathered oils even though most of the low 

 molecular weight material from both oils was 

 either evaporated or soiubilized in the under- 

 lying water during the 36-h weathering 

 period. 



Reproduction 



During the nesting season, small amounts 

 of oil on the plumage of birds can have very 

 serious effects on reproduction. The oil com- 

 pounds that are involved, however, are essen- 

 tially unknown and no extensive tests have 

 been reported. 2 



Oil washed ashore on a small island in West 

 Germany where terns (chiefly Thalasseus 

 sandvicensis and Sterna hirundo) and Euro- 

 pean oystercatchers (Haematopus ostralegus) 

 were nesting. During copulation, many of the 

 adult terns became dorsally smeared with oil 

 from their mate's oiled feet, but no direct 

 losses among adult terns were attributed to 

 the oil. More than 70% of the young terns 



"Reproductive effects have, however, been 

 studied since this manuscript was written (see 

 Szaro 1977). 



