THE GENERAL BIOLOGY O F PENGUINS
163
expect to find them in local stocks of any species which, over its geographical breeding range, appears to span sea temperature ranges of
more than 4-6°C.
Strikingly few penguins are recorded as vagrants on the southern or
colder side of their breeding ranges. Unlike whales and young elephant
seals, penguins of temperate latitudes do not seem to be tempted southward in summer by the abundance of food in Antarctic waters. Rowan
(in Swales, 1965, p. 31) assumes that Tristan and Gough Island birds
migrate southward in winter. Peruvian penguins, with a southern
breeding limit in 33"20'S, range a further 550 miles (880 km) southward
to Corral, Chile, presumably as juvenile or non-breeding birds (Murphy,
1936, p. 452; Housse, 1941, p. 105). Some interesting southern recoveries
include that of a Chinstrap penguin at Cape Royds (77"s; Murray in
Shackleton, 1909, p. 258), a Macaroni, reported off Thurston Island
(72"s; Polar Record, 1960, p. 289), and a Royal penguin from Macquarie
Island on the Balleny Islands (68"s; Kinksy, personal communication).
However, the southerly movement of warm-water homiotherms into
Antarctic water may be restricted to very much larger animals, whose
smaller surface-to-volume ratio makes them more independent of major
shifts in sea-water temperature.
2. Terrestrial Climates
The terrestrial habitats of penguins are more varied than their marine
aquatic habitats, and subject to wide temperature fluctuations, precipitation and wind which could seriously affect thermal balance. On bare
sunbaked islands off the African, dustralian and South American coasts,
tropical penguins frequently encounter air a t or near their own blood
temperature. Polar species spend their summers in air close to freezing
point, and cannot avoid sub-zero air temperatures even when wintering
at the northern edges of their range. Emperor penguins breeding through
the Antarctic winter may incubate at -40°C or less, often in gales and
drifting snow. The sub-Antarctic and cold temperate islands, where
many species breed, tend to be cold and wet, with persistent chilling
winds and overcast skies. Although in snow-covered areas summer
temperatures seldom rise far a.bove freezing point, because of the
buffering absorption of latent heat by melting snow, they may fall
rapidly with an influx of cold air and rise only a few moments later with
the advent of a fohn wind or sea-warmed airstream from the north.
Abrupt changes of 10-20°C are not uncommon in Antarctica (Lamb,
1964, p. 280) and changes of more than 23°C in an hour have been
recorded (personal observations).
The seasonal temperature characteristics of some island and southern
continental climatic stations are shown in Fig. 8a-e: for derivations see
163
expect to find them in local stocks of any species which, over its geographical breeding range, appears to span sea temperature ranges of
more than 4-6°C.
Strikingly few penguins are recorded as vagrants on the southern or
colder side of their breeding ranges. Unlike whales and young elephant
seals, penguins of temperate latitudes do not seem to be tempted southward in summer by the abundance of food in Antarctic waters. Rowan
(in Swales, 1965, p. 31) assumes that Tristan and Gough Island birds
migrate southward in winter. Peruvian penguins, with a southern
breeding limit in 33"20'S, range a further 550 miles (880 km) southward
to Corral, Chile, presumably as juvenile or non-breeding birds (Murphy,
1936, p. 452; Housse, 1941, p. 105). Some interesting southern recoveries
include that of a Chinstrap penguin at Cape Royds (77"s; Murray in
Shackleton, 1909, p. 258), a Macaroni, reported off Thurston Island
(72"s; Polar Record, 1960, p. 289), and a Royal penguin from Macquarie
Island on the Balleny Islands (68"s; Kinksy, personal communication).
However, the southerly movement of warm-water homiotherms into
Antarctic water may be restricted to very much larger animals, whose
smaller surface-to-volume ratio makes them more independent of major
shifts in sea-water temperature.
2. Terrestrial Climates
The terrestrial habitats of penguins are more varied than their marine
aquatic habitats, and subject to wide temperature fluctuations, precipitation and wind which could seriously affect thermal balance. On bare
sunbaked islands off the African, dustralian and South American coasts,
tropical penguins frequently encounter air a t or near their own blood
temperature. Polar species spend their summers in air close to freezing
point, and cannot avoid sub-zero air temperatures even when wintering
at the northern edges of their range. Emperor penguins breeding through
the Antarctic winter may incubate at -40°C or less, often in gales and
drifting snow. The sub-Antarctic and cold temperate islands, where
many species breed, tend to be cold and wet, with persistent chilling
winds and overcast skies. Although in snow-covered areas summer
temperatures seldom rise far a.bove freezing point, because of the
buffering absorption of latent heat by melting snow, they may fall
rapidly with an influx of cold air and rise only a few moments later with
the advent of a fohn wind or sea-warmed airstream from the north.
Abrupt changes of 10-20°C are not uncommon in Antarctica (Lamb,
1964, p. 280) and changes of more than 23°C in an hour have been
recorded (personal observations).
The seasonal temperature characteristics of some island and southern
continental climatic stations are shown in Fig. 8a-e: for derivations see