244
A. NELSON-SMITH
water surface; gulls (Larus spp.), gannets (Sula spp.) and their relatives
are far more aerial, whereas waders feed on slioras and mudbanks.
Auks and divers swim for some distance underwater and if they surface
in an oil-slick their backs and wings become covered. Bourne (1 968b)
observed that their immediate raaction to oil was to dive again, but in
any large-scale pollution this would almost certainly rasult in further
oiling. Gulls, swimming into oil on the surface, flew off. I n contrast,
long-tailed duck CZanguEa hyemdis (L.) in the Baltic are reported to
settle preferentially in oil patches (International Committee for Bird
Preservation, 1960 ; Lemmetyinen, 1966).
The primary effect of oil on sea-birds is t o penetrate or cling t o their
plumage, which mats the feather structura. I n a lightly-oiled bird,
water can then fill the spaces in which air is usually trapped, eliminating
heat-insulation and reducing buoyancy (Portier and Raffy, 1934 ;
T h i n g , 1952; Hartung, 1967; Goethe, 1968). A mora heavily oiled
bird is physically weighted down so that its swimrniiig movements are
impeded and flight becomes impossible (Figs. 5 and 6). It has been
stated repeatedly (Dennis, 1959; Tuck, 1960; Hawkes, 1961) that a
spot of oil 2-3 cm in diameter on the breast of a bird is enough to
bring about death, at least in the colder seas. On the other hand,
Erickson (1962) reports that up t o one-half the coastal ducks shot by
hunters in the north-eastern United States showed “ oil-burn ” and
many had tainted flesh, although they were otherwise healthy. Even
a light oiling causes birds to come ashore if possible, whera they preen
incessantly. This further damages their feather structure. They are
disinclined to feed, but are certain to ingest quantities of the oil
(Hawkes, 1961 ; Goethe, 1968). Hartung (1963) extracted an average
of 3.6 g oil from the plumage of medium-sized scaup (Aythya sp.) found
dead and ‘‘ moderately ” oiled. His experiments showed that a single
dose of one-third this quantity had marked effects on mobility, although it was not fatal. A later sample (Hartung, 1965a) had plumage
soaked with an average of 7 g oil. Ducks preen approximately half the
polluting oil from their feathers within a week, most of it on the first
day of oiling. The oils fed to ducks (Anas pzatyrhynchos L. and A .
rubripes Brewster) by Hartung and Hunt (1 966) caused lipid pnedmonia, severe intestinal irritation, fatty changes in the liver, necrosis
and adrenal enlargement. Nervous abnormalities, suggesting inhibition
of anti-cholinesterase activity, also reported, were probably due to
organic phosphate additives in the samples of diesel and cutting oils.
Amongst birds kept in optimal conditions, the amounts fed were
relatively non-toxic ; all survived doses of up to 20 ml/kg body-weight
of lubricating and 24 ml/kg of diesel oil. The toxicity was greatly
A. NELSON-SMITH
water surface; gulls (Larus spp.), gannets (Sula spp.) and their relatives
are far more aerial, whereas waders feed on slioras and mudbanks.
Auks and divers swim for some distance underwater and if they surface
in an oil-slick their backs and wings become covered. Bourne (1 968b)
observed that their immediate raaction to oil was to dive again, but in
any large-scale pollution this would almost certainly rasult in further
oiling. Gulls, swimming into oil on the surface, flew off. I n contrast,
long-tailed duck CZanguEa hyemdis (L.) in the Baltic are reported to
settle preferentially in oil patches (International Committee for Bird
Preservation, 1960 ; Lemmetyinen, 1966).
The primary effect of oil on sea-birds is t o penetrate or cling t o their
plumage, which mats the feather structura. I n a lightly-oiled bird,
water can then fill the spaces in which air is usually trapped, eliminating
heat-insulation and reducing buoyancy (Portier and Raffy, 1934 ;
T h i n g , 1952; Hartung, 1967; Goethe, 1968). A mora heavily oiled
bird is physically weighted down so that its swimrniiig movements are
impeded and flight becomes impossible (Figs. 5 and 6). It has been
stated repeatedly (Dennis, 1959; Tuck, 1960; Hawkes, 1961) that a
spot of oil 2-3 cm in diameter on the breast of a bird is enough to
bring about death, at least in the colder seas. On the other hand,
Erickson (1962) reports that up t o one-half the coastal ducks shot by
hunters in the north-eastern United States showed “ oil-burn ” and
many had tainted flesh, although they were otherwise healthy. Even
a light oiling causes birds to come ashore if possible, whera they preen
incessantly. This further damages their feather structure. They are
disinclined to feed, but are certain to ingest quantities of the oil
(Hawkes, 1961 ; Goethe, 1968). Hartung (1963) extracted an average
of 3.6 g oil from the plumage of medium-sized scaup (Aythya sp.) found
dead and ‘‘ moderately ” oiled. His experiments showed that a single
dose of one-third this quantity had marked effects on mobility, although it was not fatal. A later sample (Hartung, 1965a) had plumage
soaked with an average of 7 g oil. Ducks preen approximately half the
polluting oil from their feathers within a week, most of it on the first
day of oiling. The oils fed to ducks (Anas pzatyrhynchos L. and A .
rubripes Brewster) by Hartung and Hunt (1 966) caused lipid pnedmonia, severe intestinal irritation, fatty changes in the liver, necrosis
and adrenal enlargement. Nervous abnormalities, suggesting inhibition
of anti-cholinesterase activity, also reported, were probably due to
organic phosphate additives in the samples of diesel and cutting oils.
Amongst birds kept in optimal conditions, the amounts fed were
relatively non-toxic ; all survived doses of up to 20 ml/kg body-weight
of lubricating and 24 ml/kg of diesel oil. The toxicity was greatly