170
B. STONEHOUSE
south-western New Zealand) come down to the shore, penguins would find
it difficult to avoid nesting under cover. In the tropics, warm temperate
regions, and possibly even farther south, at least partial shade may be
essential to birds which not only expose a large black surface to the sun
(e.g. while incubating) but are also heavily insulated over most of their
surface as protection against heat losses in water. Most penguins in this
geographical range feed at sea during the day and are active on land
mainly a t night, a way of life which would further protect them from
excessive sun and heat.
Both undercover nesting and the nocturnal habit offer protection
against diurnal predators, a factor important in open situations (e.g.
the Chatham Islands where both skuas Catharacta skua and dogs attack;
Fleming, 1939, p. 390), but probably less so on most temperate and
tropical islands where aerial or terrestrial predators are few. Falla (1935,
p. 323) has suggested that Fjordland penguins avoid the bites of simuliid
flies by nesting in dense shade. Protection against intense light may also
be important; the White-flippered penguin, which nests in holes, spends
its days at sea, but also feeds a t night, has a fundus occuli characteristic
of nocturnal birds (O’Brien, 1940, p. 320) and may be at a disadvantage
on land during the day. Burrowing avoids interspecific competition for
nest sites on guano islands where penguins would otherwise compete
with pelicans, boobies and cormorants. In higher latitudes penguins are
able to hold their own in competition for burrows with some of the smaller
petrels (e.g. Chatham Islands and southern Chile).
The distinction between social and solitary nesting breaks down in
many situations. Solitary pairs of Emperor penguins would almost certainly fail to breed, because of excessive heat losses in adults and chicks.
Solitary pairs of pygoscelid and eudyptid penguins nearly always lose
their eggs or chicks to skuas (usually Brown skuas in the sub-Antarctic);
however, such birds are often if not always inexperienced breeders,
possibly inadequately motivated and likely in any case to fail their first
nesting trial. Gentoos on South Georgia are more colonial than those on
Macquarie, where denser tussock may provide better cover and warmth
for individual chicks. King penguins, usually breeding in large colonies
and seldom seen alone, occasionally breed successfully as solitary pairs
on South Georgia, and at the Falkland Islands (Cawkell and Hamilton,
1961, p. 5). Thus Emperors are necessarily social breeders; birds of other
social species are usually but not always unsuccessful when breeding
alone.
Among the less social species, some Galapagos penguins nest in caverns
several hundreds of metres from neighbouring pairs; others nest in small
groups, where a single cave or overhang provides accommodation for
more than one pair. Yellow-eyed penguins may breed entirely on their
B. STONEHOUSE
south-western New Zealand) come down to the shore, penguins would find
it difficult to avoid nesting under cover. In the tropics, warm temperate
regions, and possibly even farther south, at least partial shade may be
essential to birds which not only expose a large black surface to the sun
(e.g. while incubating) but are also heavily insulated over most of their
surface as protection against heat losses in water. Most penguins in this
geographical range feed at sea during the day and are active on land
mainly a t night, a way of life which would further protect them from
excessive sun and heat.
Both undercover nesting and the nocturnal habit offer protection
against diurnal predators, a factor important in open situations (e.g.
the Chatham Islands where both skuas Catharacta skua and dogs attack;
Fleming, 1939, p. 390), but probably less so on most temperate and
tropical islands where aerial or terrestrial predators are few. Falla (1935,
p. 323) has suggested that Fjordland penguins avoid the bites of simuliid
flies by nesting in dense shade. Protection against intense light may also
be important; the White-flippered penguin, which nests in holes, spends
its days at sea, but also feeds a t night, has a fundus occuli characteristic
of nocturnal birds (O’Brien, 1940, p. 320) and may be at a disadvantage
on land during the day. Burrowing avoids interspecific competition for
nest sites on guano islands where penguins would otherwise compete
with pelicans, boobies and cormorants. In higher latitudes penguins are
able to hold their own in competition for burrows with some of the smaller
petrels (e.g. Chatham Islands and southern Chile).
The distinction between social and solitary nesting breaks down in
many situations. Solitary pairs of Emperor penguins would almost certainly fail to breed, because of excessive heat losses in adults and chicks.
Solitary pairs of pygoscelid and eudyptid penguins nearly always lose
their eggs or chicks to skuas (usually Brown skuas in the sub-Antarctic);
however, such birds are often if not always inexperienced breeders,
possibly inadequately motivated and likely in any case to fail their first
nesting trial. Gentoos on South Georgia are more colonial than those on
Macquarie, where denser tussock may provide better cover and warmth
for individual chicks. King penguins, usually breeding in large colonies
and seldom seen alone, occasionally breed successfully as solitary pairs
on South Georgia, and at the Falkland Islands (Cawkell and Hamilton,
1961, p. 5). Thus Emperors are necessarily social breeders; birds of other
social species are usually but not always unsuccessful when breeding
alone.
Among the less social species, some Galapagos penguins nest in caverns
several hundreds of metres from neighbouring pairs; others nest in small
groups, where a single cave or overhang provides accommodation for
more than one pair. Yellow-eyed penguins may breed entirely on their