THE GENERAL BIOLOGY OF PENGUINS
147
depressions bring a variety of air temperatures from freezing point to
23°C. At sea level rainfall is about 200 cm annually on Tristan, 50%
more on Gough (Swales, 1965, p. 21). Dominant vegetation is maritime
tussock grass up to 3.5 m tall (Moseley, 1879, p. 117; Wace, 1960, p. 479
and pl. 35), where Rockhoppers nest in soft humus and gain protection
from wind, rain and aerial predators. They return from migration to
Tristanin mid-August, and to Gough about three weekslater; two eggs are
the rule at Gough, but Elliott (1957, p. 555) reported many three-egg
clutches at Tristan (Swales, 1965, p. 31). Only one chick normally
survives from each clutch.
St. Paul and New Amsterdam. These lie close to the sub-tropical convergence in the Indian Ocean, in the westerly wind zone for most of the
year. Similar in size to the Atlantic warm temperate islands, they have
suffered greater devastation from goats and other introduced animals
but are otherwise a close match. Rockhopper penguins are plentiful in
large colonies (Jeannel, 1941, p. 122; Paulian, 1953, p. 147), among
tussock and in caverns and tunnels of the lava rock. They return from
migration in early September and lay three weeks later.
e. Cold temperate islands
Five island groups provide important penguin breeding grounds between the sub-tropical and sub-Antarctic convergences.
Falkland Islands. The Falkland archipelago includes two large and
many small islands, low-lying and totalling over 4 500 square miles. The
Falkland current brings cold water ( 6 9 ° C ) from south and west; west
and northwest winds predominate, and temperatures are mild with only
slight seasonal variation (Fig. 8a). The two main islands are cropped by
sheep; native vegetation appears on the islets, which bear dense tussock
grass, merging into low heathland. Magellanic penguins burrow in sand
dunes and clay banks close to the sea, Gentoos nest on flat ground
among the tussock, and Rockhoppers nest in longer tussock on the cliffs
and steep hillsides. A few Macaronis are found among the Rockhoppers,
and single pairs of King penguins have attempted to breed, with indifferent success, on coastal flats during the past 20 years (Cawkell and
Hamilton, 1961, p. 5). All species breed in spring; only Gentoos (and
possible Kings) are resident throughout the year.
Marion and Prince Edward Isslands. Marion Island, roughly circular
with diameter about 12 miles (19 km), rises to over 4 000 ft ( 1 200 m)
and is permanently snow-capped. Prince Edward Island, 19 miles (24
km) to the north, is smaller and steeper but otherwise similar. Both have
coastal cliffs alternating with beaches, and extensive swampy tussock
meadows inland. They stand squarely in the West Wind Drift, close t o
the Antarctic convergence. Prevailing northwesterly winds are cooled
147
depressions bring a variety of air temperatures from freezing point to
23°C. At sea level rainfall is about 200 cm annually on Tristan, 50%
more on Gough (Swales, 1965, p. 21). Dominant vegetation is maritime
tussock grass up to 3.5 m tall (Moseley, 1879, p. 117; Wace, 1960, p. 479
and pl. 35), where Rockhoppers nest in soft humus and gain protection
from wind, rain and aerial predators. They return from migration to
Tristanin mid-August, and to Gough about three weekslater; two eggs are
the rule at Gough, but Elliott (1957, p. 555) reported many three-egg
clutches at Tristan (Swales, 1965, p. 31). Only one chick normally
survives from each clutch.
St. Paul and New Amsterdam. These lie close to the sub-tropical convergence in the Indian Ocean, in the westerly wind zone for most of the
year. Similar in size to the Atlantic warm temperate islands, they have
suffered greater devastation from goats and other introduced animals
but are otherwise a close match. Rockhopper penguins are plentiful in
large colonies (Jeannel, 1941, p. 122; Paulian, 1953, p. 147), among
tussock and in caverns and tunnels of the lava rock. They return from
migration in early September and lay three weeks later.
e. Cold temperate islands
Five island groups provide important penguin breeding grounds between the sub-tropical and sub-Antarctic convergences.
Falkland Islands. The Falkland archipelago includes two large and
many small islands, low-lying and totalling over 4 500 square miles. The
Falkland current brings cold water ( 6 9 ° C ) from south and west; west
and northwest winds predominate, and temperatures are mild with only
slight seasonal variation (Fig. 8a). The two main islands are cropped by
sheep; native vegetation appears on the islets, which bear dense tussock
grass, merging into low heathland. Magellanic penguins burrow in sand
dunes and clay banks close to the sea, Gentoos nest on flat ground
among the tussock, and Rockhoppers nest in longer tussock on the cliffs
and steep hillsides. A few Macaronis are found among the Rockhoppers,
and single pairs of King penguins have attempted to breed, with indifferent success, on coastal flats during the past 20 years (Cawkell and
Hamilton, 1961, p. 5). All species breed in spring; only Gentoos (and
possible Kings) are resident throughout the year.
Marion and Prince Edward Isslands. Marion Island, roughly circular
with diameter about 12 miles (19 km), rises to over 4 000 ft ( 1 200 m)
and is permanently snow-capped. Prince Edward Island, 19 miles (24
km) to the north, is smaller and steeper but otherwise similar. Both have
coastal cliffs alternating with beaches, and extensive swampy tussock
meadows inland. They stand squarely in the West Wind Drift, close t o
the Antarctic convergence. Prevailing northwesterly winds are cooled