I42
B. STONEHOUSE
eastern seaboards are dominated respectively by the Peruvian and
Falkland cold currents.
Galapagos Islands. Sea conditions about the Galapagos archipelago
have been described by Schott (1935, p. 308-313) and Murphy (1936,
p. 296-303). The islands stand a t the junction of oceanic currents from
north, west and south-east. The southern and western islands Albemarle
and Narborough, where Galapagos penguins breed, lie in the northern
extension of the Peruvian current (see below) a t sea temperatures of
20-25"C, some 5°C lower than the equatorial mean (Fig. 7). LBv6que's
climatic summary (1964, p. 6) for the coast of Chatham, based on data
from Blandin Landivar (1959), shows a marked seasonal shift of air
temperature from approximately 17°C (September) to 32°C (March).
Most penguins breed in May-July when mean sea and air temperatures
are falling from 25°C to 22°C or lower. Insolation is usually intense, but
the penguins nest in caves or cavities among rocks close to the sea -
probably the coolest and least variable terrestrial environment available
a t sea level.
Peru and north Chile. The marine environment is entirely dominated
by the Peruvian current. Cold sub-dntarctic water sweeps up the coast
of southern Chile from the West Wind Drift, a t a rate approaching 12
miles (19 km) per day. About latitude 30"s it joins northward-moving
masses of upwelled water, cool (14-18°C) and rich in oxygen and mineral
salts. Upwelling is continuous along the coast to 5'5, so that the current
remains anomalously cool ; deflected westward from the coast just south
of the equator, it, carries cool water past the Galapagos to join the South
Equatorial Current. Coastal air temperatures are controlled by water
temperatures (Fig. 7 - Callao and Valparaiso), and cool air forced up
the steep coastral terraces produces cloudy conditions which temper
insolation.
Peruvian penguins breed on offshore islands from 6'30% to approximately 33"S, entirely within the Peruvian current but extending farther
south than the major upwelling regions. They nest in caverns and
burrows in shingle or firm sand; originally they burrowed mainly in vast
banks of consolidated guano, which has now been stripped from the
islands (Murphy, 1936, p. 453). They probably breed throughout the
year. The small shoaling fish which are their main food (see below) are
apparently abundant throughout the year.
Juan Fernandez. Mas a Tierra, 420 miles (660 Itm) west of Valparaiso,
lies a t the western boundary of the Peruvian current. Small numbers of
Magellanic penguins make it the most northerly breeding station of the
species (Lonnberg, 1921, p. 16; Murphy, 1936, p. 444). Ranges of Magellanic and Peruvian penguins overlap between the 30th and 40th parallels:
the success of the former in colonizing this island may be due to their
B. STONEHOUSE
eastern seaboards are dominated respectively by the Peruvian and
Falkland cold currents.
Galapagos Islands. Sea conditions about the Galapagos archipelago
have been described by Schott (1935, p. 308-313) and Murphy (1936,
p. 296-303). The islands stand a t the junction of oceanic currents from
north, west and south-east. The southern and western islands Albemarle
and Narborough, where Galapagos penguins breed, lie in the northern
extension of the Peruvian current (see below) a t sea temperatures of
20-25"C, some 5°C lower than the equatorial mean (Fig. 7). LBv6que's
climatic summary (1964, p. 6) for the coast of Chatham, based on data
from Blandin Landivar (1959), shows a marked seasonal shift of air
temperature from approximately 17°C (September) to 32°C (March).
Most penguins breed in May-July when mean sea and air temperatures
are falling from 25°C to 22°C or lower. Insolation is usually intense, but
the penguins nest in caves or cavities among rocks close to the sea -
probably the coolest and least variable terrestrial environment available
a t sea level.
Peru and north Chile. The marine environment is entirely dominated
by the Peruvian current. Cold sub-dntarctic water sweeps up the coast
of southern Chile from the West Wind Drift, a t a rate approaching 12
miles (19 km) per day. About latitude 30"s it joins northward-moving
masses of upwelled water, cool (14-18°C) and rich in oxygen and mineral
salts. Upwelling is continuous along the coast to 5'5, so that the current
remains anomalously cool ; deflected westward from the coast just south
of the equator, it, carries cool water past the Galapagos to join the South
Equatorial Current. Coastal air temperatures are controlled by water
temperatures (Fig. 7 - Callao and Valparaiso), and cool air forced up
the steep coastral terraces produces cloudy conditions which temper
insolation.
Peruvian penguins breed on offshore islands from 6'30% to approximately 33"S, entirely within the Peruvian current but extending farther
south than the major upwelling regions. They nest in caverns and
burrows in shingle or firm sand; originally they burrowed mainly in vast
banks of consolidated guano, which has now been stripped from the
islands (Murphy, 1936, p. 453). They probably breed throughout the
year. The small shoaling fish which are their main food (see below) are
apparently abundant throughout the year.
Juan Fernandez. Mas a Tierra, 420 miles (660 Itm) west of Valparaiso,
lies a t the western boundary of the Peruvian current. Small numbers of
Magellanic penguins make it the most northerly breeding station of the
species (Lonnberg, 1921, p. 16; Murphy, 1936, p. 444). Ranges of Magellanic and Peruvian penguins overlap between the 30th and 40th parallels:
the success of the former in colonizing this island may be due to their