The Rockhopper penguin is a group of penguins that are
closely related and share the same love of jumping over rocks to get about,
rather sliding around on their bellies in the normal penguin fashion. There are
three different species of rockhopper penguin which are the western rockhopper
penguin, the eastern rockhopper penguin and the northern rockhopper penguin.
Rockhopper penguins are found throughout the sub-Antarctic
and in regions of the southern Indian and Pacific Oceans. The regions occupied
by the rockhopper penguin depend on the species. The western rockhopper is
found around the tip of the South America; the eastern rockhopper breeds on
sub-Antarctic islands of the Indian and western Pacific oceans and the northern
rockhopper penguin breeds on islands of Tristan da Cunha as well as on
Amsterdam and St Paul Islands.
Identification
Rockhoppers are distinguished from other crested penguins by
their smaller size and by having only a thin yellow superscilium. The feather
plumes are yellow, not orange as in Macaroni Penguin, and thinner than in the
remaining Eudyptes species. The red eye is distinctive. Southern Rockhopper
Penguins differ from their Northern counterparts in having a narrower
supercilium and shorter plumes, which reach just over the black throat. Their
vocalisations are also different. The Southern Rockhopper actually comprises
two subspecies that have been described and can be identified in the field: the
nominate form from South America and the Falkland Islands and the eastern subspecies
filholi from the New Zealand sub-Antarctic islands. The eastern form mainly
differs from the nominate subspecies in having a pink line of fleshy skin along
the lower mandible which is black in the nominate subspecies. Immature birds
have only a narrow supercilium and a pale mottled grey chin. Identification of
juveniles is difficult. Shape of the supercilium, bill shape, body size and
underwing pattern can aid identification. Separation of juvenile Southern and
Northern Rockhopper Penguins in the field is probably impossible.
Feeding
The diet and foraging strategies of Rockhopper penguins have
been studied at a wide variety of sites. This has revealed broadly similar
foraging strategies with certain adaptations to the local environment. Diet
varies not only with location but also temporally due to seasonal changes in
relative and total prey availability. Further, significant interannual changes
in diet have been recorded at several sites, correlating to yearly fluctuations
in prey biomass. Rockhopper foraging patterns can be studied in a variety of
ways. Dietary studies are performed on breeding birds returning to colonies and
generally involve flushing the stomach contents of birds and analysing their
composition. Further, depth-loggers or satellite-tracking devices can be
attached to the backs of penguins to provide data on diving behaviour and
foraging ranges.
Characteristics
Rockhopper Penguins are named after the way they hop from
rock to rock when moving around their colonies. They reach heights up to 55 cms
(21 inches) and they weigh between 2 and 3 kgs (4.5 - 6.5 lbs).
Their head and back are blue/black in colour and they have a
white coloured front. They have a yellow line along their brow which extends to
a feathery crest. They have small red eyes and a orange coloured beak.
Rockhopper Penguins are loud, aggressive birds and they use
a call known as "ecstatic vocalization" to attract mates. As well as
vocalizing they also communicate by head shaking, bowing, preening, and head
and flipper waving.
Behaviour
Rockhopper Penguin colonies are often relatively small
compared with other penguin species but what they lack in size they make up for
in noise. Fierce competition for nesting materials, mating partners and
territory all contribute to the cacophony of sound at these sites. As well as
vocalizing, these birds communicate by head shaking, head and flipper waving,
bowing, gesturing and preening.
Physical Features
Adults of both species are small in stature compared with
other penguins. Most adults stand under 52–55 cm (about 20–22 inches) tall and
weigh 2.5–3 kg (5.5–6.6 pounds). Although males are slightly larger than
females, adult members of both sexes have red eyes, a red-brown beak, and
prominent superciliary stripes, in addition to black feathers on their head,
throat, and back that contrast with their white underside. Juveniles resemble
adults in most respects. Some juveniles have lighter-coloured superciliary
stripes, whereas other juveniles have no stripes at all. All juveniles possess mottled
gray plumage underneath the chin. Rockhopper chicks, however, have a black
bill, gray plumage on the head and back, and a white underside. The outward
appearance of northern rockhopper penguins is distinguished from that of
southern rockhopper penguins by the presence of a slightly thicker superciliary
stripe.
Diet
Rockhopper penguins are carnivores (meat-eaters) that catch
their prey in the ocean. Their diet consists mostly of crustaceans and small
fish.
Reproduction
The breeding season varies according to the range. The
Southern Rockhopper Penguin breeds in colonies from sea-level to cliff-tops,
and sometimes inland. The nest is a scrape in the ground, often lined with
dried grasses, but other materials can be found, such as stones or bones.
The female lays two eggs and the incubation lasts 32-34
days, shared by both adults. They take turns with stints of 7 to 17 days. The
chick is brooded by the male while the female brings the food, but the male is
able to provide “milk” which is regurgitated for the chicks.
When the young are 3 weeks old, they gather at crèches with
other chicks, where they are protected and reared. They moult and leave the
nesting grounds for the open sea about 65-72 days after hatching. They can live
about ten years.
How many Rockhopper Penguins are there today?
A rough estimate places the worldwide Rockhopper Penguin population at over 7,000,000, but they’ve suffered a drastic 30% population drop over the last 30 years due to pollution and other man-made examples of interference.
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