Observation of an Encounter between Birds and Floating Oil

Abstract

ALTHOUGH oil pollution has been a growing hazard to water birds for half a century1, little information is available about how it occurs. Curry-Lindahl2 has remarked that in the Baltic flocks of long-tailed duck, Clangula hyemalis, “very often swoop down just on the patches of oil where the deep sea roll is less heavy; consequently these oil spots serve as veritable death traps”, whereas Casement3 has reported that where Manx shearwaters, Puffinus puffinus, were flying up the Bosphorus the passage of a patch of oil “caused birds to rise a few feet as flocks passed over it and then swoop down again to within a few feet of the sea”. Otherwise widely repeated 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 speculation. There has therefore been a need for critical observations of how birds actually do behave when they encounter oil.