190
B. STONEHOUSE
Southern Gentoos are also negative in both respects, almost meriting
double symbols (Figs. 10a and lOc), and are clearly a well-adapted form
of their species. They share only the northern breeding grounds of
Addies in the Antarctic Peninsula-Scotia Arc area, and are probably
able to penetrate so far south only because of the remarkably mild
summers in this sector (Stonehouse, 1964, p. 228). Chinstraps also are
negative on both counts but lack the extreme specializations of either
Addies or Southern Gentoos; they too reach high latitudes only on the
warm western coast of the Antarctic Peninsula. Macaroni penguins,
which penetrate Antarctic fringes to breed among the northernmost
stocks of Antarctic pygoscelids, seem remarkably little adapted. They
possess the rather long plumage characteristic of their genus, and usually
nest in the protection of rocks on warm, sunny slopes. Otherwise they
seem barely specialized for polar life even on the edge of Antarctica.
Among tropical species, Peruvian and Blackfooted penguins seem
most obviously adapted for shedding body heat, scoring respectively
four and three positive marks. The thin plumage characteristic of their
genus is shared to varying degrees by Galapagos and Magellanic penguins, but Peruvian and Blackfooted penguins have the large flippers of
bare island populations, while their congeners have proportionately
smaller extremities consistent with their more cryptic habit on land.
The special facial areas, prominent in Peruvian penguins, are also important in this context. Galapagos penguins, seemingly less specialized
although living in the warmest environment (Fig. 7), probably score
from their smaller body size with its comparatively larger surface area.
Among eudyptulid penguins the Chatham Island sub-species has B
strong positive score, distinguishing it sharply from its parent Southern
Blue stock. Northern Blue penguins follow closely, with plumage only
moderately short for their size but a comparatively large flipper. Like
Galapagos penguins, all the eudyptulids may be expected to lose heat
at a considerable rate through their relatively large surface; it is possibly
surprising that the Southern Blue and White-flippered penguins have
such short plumage, although their comparatively stocky build, perhaps
with rather more subcutaneous fat, may help them to conserve heat in
cool southern waters.
The remaining species are less clearly modified for extreme heat or
cold. All the eudyptid penguins have plumage on the long side, possibly
suggesting a cool temperate origin for the genus; their flippers tend to
be large, markedly so in the Erect-crested, but also in the Royal and
(surprisingly) the Macaroni. In contrast, King and Yellow-eyed penguins
tend to have short plumage and rather small flippers. Fjordland,
Northern Gentoo and Southern Blue penguins most closely approach
neutrality on both scores.
B. STONEHOUSE
Southern Gentoos are also negative in both respects, almost meriting
double symbols (Figs. 10a and lOc), and are clearly a well-adapted form
of their species. They share only the northern breeding grounds of
Addies in the Antarctic Peninsula-Scotia Arc area, and are probably
able to penetrate so far south only because of the remarkably mild
summers in this sector (Stonehouse, 1964, p. 228). Chinstraps also are
negative on both counts but lack the extreme specializations of either
Addies or Southern Gentoos; they too reach high latitudes only on the
warm western coast of the Antarctic Peninsula. Macaroni penguins,
which penetrate Antarctic fringes to breed among the northernmost
stocks of Antarctic pygoscelids, seem remarkably little adapted. They
possess the rather long plumage characteristic of their genus, and usually
nest in the protection of rocks on warm, sunny slopes. Otherwise they
seem barely specialized for polar life even on the edge of Antarctica.
Among tropical species, Peruvian and Blackfooted penguins seem
most obviously adapted for shedding body heat, scoring respectively
four and three positive marks. The thin plumage characteristic of their
genus is shared to varying degrees by Galapagos and Magellanic penguins, but Peruvian and Blackfooted penguins have the large flippers of
bare island populations, while their congeners have proportionately
smaller extremities consistent with their more cryptic habit on land.
The special facial areas, prominent in Peruvian penguins, are also important in this context. Galapagos penguins, seemingly less specialized
although living in the warmest environment (Fig. 7), probably score
from their smaller body size with its comparatively larger surface area.
Among eudyptulid penguins the Chatham Island sub-species has B
strong positive score, distinguishing it sharply from its parent Southern
Blue stock. Northern Blue penguins follow closely, with plumage only
moderately short for their size but a comparatively large flipper. Like
Galapagos penguins, all the eudyptulids may be expected to lose heat
at a considerable rate through their relatively large surface; it is possibly
surprising that the Southern Blue and White-flippered penguins have
such short plumage, although their comparatively stocky build, perhaps
with rather more subcutaneous fat, may help them to conserve heat in
cool southern waters.
The remaining species are less clearly modified for extreme heat or
cold. All the eudyptid penguins have plumage on the long side, possibly
suggesting a cool temperate origin for the genus; their flippers tend to
be large, markedly so in the Erect-crested, but also in the Royal and
(surprisingly) the Macaroni. In contrast, King and Yellow-eyed penguins
tend to have short plumage and rather small flippers. Fjordland,
Northern Gentoo and Southern Blue penguins most closely approach
neutrality on both scores.