REVIEW ARTICLE - EFFECTS OF OIL POLLUTION, CHEMICALLY TREATED OIL, AND CLEANING ON THE THERMAL BALANCE OF BIRDS

The acute effect of oil pollution on birds is on their thermal balance . Oil adheres to the plumage and causes a reduction in the water repel lent properties of the plumage, causing water to penetrate into the pl umage to displace the insulating layer of air. The effect of oil on th e plumage insulation is dose-dependent. The effect of oiling is greatl y enhanced when the oil is spread in the plumage due to preening. In w ater, plumage oiling may cause the heat loss to exceed the bird's heat production capacity, resulting in hypothermia. If the oiled bird is a shore, with a dry plumage, it may have a normal thermal insulation. Bi rd species dependent upon feeding in water (such as diving birds) are therefore much more susceptible to the harmful effects of oil pollutio n than are semi-aquatic species that can feed ashore. It is possible t o restore the water-repelling and insulative properties of the plumage by the process of cleaning if all the oil and soap is removed, and if the plumage is completely dry. Chemical treatment of oil has been sug gested as a way to reduce the impact of oil spills on avian life. Howe ver, very few reports seem to have addressed the effects of chemically treated oil on the thermal balance of birds, and the results from one study actually indicate that oil treated with dispersants may be more harmful to birds than oil. The urgent need for more information about the effects of chemically treated oil on aquatic birds is therefore s tressed.