172
B. STONEHOUSE
live in the same restricted locality as the entirely flightless cormorant
Nannopterum harrisi (LBveque, 1964, pp. 10, 25), suggesting that any
large vertebrate carnivores in the area must have other and more profitable sources of food, or are for some reason excluded from the waters
close to the two breeding islands.
On land man is a serious predator of some species and a source of
dangerous interference to others. LBv6que (1963, p. 417) regards fishermen and yachtsmen as the greatest enemies of the Galapagos penguin,
in spite of the species' remoteness and retiring habit. With the removal
of consolidated guano from islands in the Peruvian and Benguela current,
stocks of Peruvian and Blackfooted penguins have suffered permanent
reduction. Hunting, for oil and plumage, devastated colonial species of
the cold temperate and sub-antarctic zones in the 19th and early 20th
centuries, and egg collecting under license has devastated many colonies
on the Falkland Islands. Antarctic colonies, raided spasmodically for
food by earlier exploring parties, now suffer more continuous interference
from humans, sledge dogs and low flying aircraft. The Ad6lie penguin
colony at Cape Royds, McMurdo Sound (78"S), declined from about
2 000 pairs in 1956 to a little over 1 000 pairs in 1963, due to serious interference by helicopters and visitors from a large expedition base nearby.
Disturbance affected recruitment by young birds rather than breeding
success, and was reduced by supervision and more effective flying
regulations (Stonehouse, 1963, p. 766, 1965, pp. 5-6). Bush clearance,
agriculture, road building and settlement have displaced penguins in
Patagonia, southern Chile, Australia and New Zealand, and introduced
mammals (foxes, pigs, goats, rats, sheep, cats, mustelids, dogs) and other
alien species have been credited with the devastation of many breeding
areas by direct predation or destruction of habitat.
Natural land predators include skua gulls, which take eggs and chicks
of many Antarctic, sub-Antarctic and temperate species. Their role was
perhaps overemphasized by earlier writers: recent studies have shown
that a strong territorial system keeps all but a few resident skuas away
from penguin colonies, that the residents are scavengers as much as
predators, and that most skuas - including many resident on penguin
colonies -take much of their food directly from the sea (Stonehouse,
1953, pp. 10-11; Young, 1963). Sheathbills Chionis a h , Lesser sheathbills Chionis minor and Dominican gulls Larus dominicanus also scavenge
on penguin colonies, taking unguarded eggs and chicks. Giant petrels
Macronectes giganteus attack small chicks of King and Emperor penguins
(Stonehouse, 1960, p. 53; PrBvost, 1061, p. 167), especially in winter and
early spring when the sea is frozen or planktonic foods scarce. At Gough
Island they kill freshly moulted Rockhoppers which, entering the water
after five weeks of starvation, are too weak to escape (Swales, 1965, p. 31).
B. STONEHOUSE
live in the same restricted locality as the entirely flightless cormorant
Nannopterum harrisi (LBveque, 1964, pp. 10, 25), suggesting that any
large vertebrate carnivores in the area must have other and more profitable sources of food, or are for some reason excluded from the waters
close to the two breeding islands.
On land man is a serious predator of some species and a source of
dangerous interference to others. LBv6que (1963, p. 417) regards fishermen and yachtsmen as the greatest enemies of the Galapagos penguin,
in spite of the species' remoteness and retiring habit. With the removal
of consolidated guano from islands in the Peruvian and Benguela current,
stocks of Peruvian and Blackfooted penguins have suffered permanent
reduction. Hunting, for oil and plumage, devastated colonial species of
the cold temperate and sub-antarctic zones in the 19th and early 20th
centuries, and egg collecting under license has devastated many colonies
on the Falkland Islands. Antarctic colonies, raided spasmodically for
food by earlier exploring parties, now suffer more continuous interference
from humans, sledge dogs and low flying aircraft. The Ad6lie penguin
colony at Cape Royds, McMurdo Sound (78"S), declined from about
2 000 pairs in 1956 to a little over 1 000 pairs in 1963, due to serious interference by helicopters and visitors from a large expedition base nearby.
Disturbance affected recruitment by young birds rather than breeding
success, and was reduced by supervision and more effective flying
regulations (Stonehouse, 1963, p. 766, 1965, pp. 5-6). Bush clearance,
agriculture, road building and settlement have displaced penguins in
Patagonia, southern Chile, Australia and New Zealand, and introduced
mammals (foxes, pigs, goats, rats, sheep, cats, mustelids, dogs) and other
alien species have been credited with the devastation of many breeding
areas by direct predation or destruction of habitat.
Natural land predators include skua gulls, which take eggs and chicks
of many Antarctic, sub-Antarctic and temperate species. Their role was
perhaps overemphasized by earlier writers: recent studies have shown
that a strong territorial system keeps all but a few resident skuas away
from penguin colonies, that the residents are scavengers as much as
predators, and that most skuas - including many resident on penguin
colonies -take much of their food directly from the sea (Stonehouse,
1953, pp. 10-11; Young, 1963). Sheathbills Chionis a h , Lesser sheathbills Chionis minor and Dominican gulls Larus dominicanus also scavenge
on penguin colonies, taking unguarded eggs and chicks. Giant petrels
Macronectes giganteus attack small chicks of King and Emperor penguins
(Stonehouse, 1960, p. 53; PrBvost, 1061, p. 167), especially in winter and
early spring when the sea is frozen or planktonic foods scarce. At Gough
Island they kill freshly moulted Rockhoppers which, entering the water
after five weeks of starvation, are too weak to escape (Swales, 1965, p. 31).