One of the six species of crested penguin, the rockhopper is circumpolar
in distribution. Adults often have white stripes on the cheeks, juveiles
have a shorter crest and pale cheeks. One of the smallest of the crested
penguins, the rockhopper stands at approx 40cm and weighs up to 4kg.
Easily distinguished as adults by their prominent yellow crest and
bright red eyes - all other crested penguins have darker eyes. Sexes
alike, although males are larger with more robust bills. Juveniles
have only a faint crest and have white mottling on the chin and throat.
Inhabitants of the sun-antarctic oceans, the rockhoppers breed in
colonies on rocky coasts, often climbing very steep faces to breed
under overhangs or caves. Will often breed alongside erect-crested
penguins. In the New Zealand region, the rockhopper can be found on
the sub-antarctic islands Campbell, Auckland and Antipodes. Juveniles
occasionally straggle to the New Zealand mainland.
The males return to their breeding colonies in October, the females
following two weeks later. Competition for nest sites can be fierce
and fighting is common. A simple nest of stones and vegetation is
made and two eggs are laid, however only the second and larger egg
is incubated. The chicks fledge in March and the adults return to
sea for the winter after moulting in April/May.
Little is known of the rockhoppers diet, but it is thought that they
are pelagic feeders, dining on fish and krill near the surface.
A study published in 2009 showed that the world population of the
Northern Rockhopper had declined by 30% since the 1950s, possibly
because of climate change, changes in marine ecosystems and overfishing
for squid and octopus by humans. Other possible factors in the decline
include disturbance and pollution from ecotourism and fishing, egg-harvesting,
predation from introduced House Mice and predation and competition
from Subantarctic Fur Seals.