The crested penguin (Eudyptes sclateri) is a penguin species with a limited distribution, breeding predominantly on the Antipodes and Bounty Islands, which belong to New Zealand. It depends on the rich fish and krill stocks of sub-Antarctic waters for food. Its population, estimated to have numbered hundreds of thousands of pairs in the mid-20th century, has declined sharply, particularly due to changes in marine ecosystems, the climate crisis, competition from fishing, oil pollution and the scarcity of breeding areas. Today, fewer than 80,000 pairs remain, leading to the species being listed as ‘Endangered’ (EN) on the IUCN Red List.

Morphological Characteristics and Systematic Position

Physical Description

The crested penguin (Eudyptes sclateri) is a medium-large bird, approximately 60–70 cm in length and reaching 3.5–6.5 kg in weight before breeding. It is notable for its dark back and upper side feathers and bright yellow crest band, which it shares with other crested penguins. The upper body is bluish-black, while the belly and underbreast are white; the colour transition on the chest and sides is distinct. A yellow superciliary stripe, starting at eye level on the face, extends to both sides of the head, forming prominent crests. Its beak is large and brownish-orange in colour, with a pale blue-white bare skin ring at the base of the beak. Its legs and feet are pinkish-pale in colour.

There is no obvious sexual dimorphism (differences between the sexes of the species) in the external appearance of adult females and males, but males are generally slightly larger and heavier. Individual differences are also seen in characteristics such as crest length or brightness. The feathers are dense, thick and water-resistant; the wings are flipper-shaped, adapted for swimming. The body shape is suited to efficient movement in water and maintaining thermoregulation (the ability to keep the body within certain limits regardless of the ambient temperature).

Taxonomy and Evolution

Taxonomically, the crested penguin (Eudyptes sclateri) belongs to the genus Eudyptes. Molecular phylogenetic studies indicate that this species diverged from other crested penguin species at an early stage.

Fossil records also support this evolutionary process. The Eudyptes atatu species found in New Zealand dates back to the Pliocene epoch (the final stage of the third geological era, which began approximately 5.3 million years ago and ended 2.5 million years ago), approximately 3.3–3.0 million years ago, and has a thinner beak compared to living crested penguin species.

Furthermore, it has been determined that the divergence of the Eudyptes genus from Megadyptes occurred approximately 15 million years ago during the Middle Miocene epoch, based on mtDNA and nuclear DNA analyses. From the Pliocene onwards, rising sea surface temperatures, wind-driven upwelling events and changes in the marine food web have been linked to changes in the beaks and feeding strategies of crested penguins.

^{Three-banded penguins on the Antipodes Islands (Flickr)}

Ecology, Behaviour and Life Cycle

Habitat and Distribution

The species forms large colonies on rocky and narrow coastal areas, primarily on the sub-Antarctic islands of the Antipodes and Bounty Islands, which belong to New Zealand. Colonies are typically located on rocks that are very low to the ground or slightly sloped, with minimal soil cover and sheltered from the wind.

During the breeding season, crested penguins use coastal waters near the colonies to feed their chicks. Observations indicate that individuals feed in areas up to several tens of kilometers from the coast during this period, with most dives occurring in shallow waters between 10 and 40 metres. Deeper dives are rarely recorded.

Nutritional Ecology

Information on the nutritional ecology of the crested penguin (Eudyptes sclateri) is limited, with existing sources revealing the main components of its diet. The diet of this species consists primarily of marine crustaceans (e.g. krill) and squid; small fish are less common.

Foraging behaviour is not fully understood, but reports indicate that the species typically forages in open seas and hunts at shallow depths near the surface, sometimes traveling hundreds of kilometers. The species hunts using a typical predatory diving (capture diving) technique. Furthermore, outside the breeding season, they live entirely in a marine environment.

Reproductive Biology

Erect-crested penguins are monogamous, and mated pairs return to the same breeding grounds each breeding season. The breeding season on the Antipodes Islands begins in October, with males arriving at the colonies before the females to defend their nesting sites, and the females joining them a few days later.

Pairs lay two eggs; the first egg is quite small and often (approximately 98%) fails due to egg loss or being displaced from the nest, while the second egg is larger and decisive for development.

The incubation period is approximately 35 days, and incubation duties are shared between the male and female. After hatching, the female remains in the nest for the first few days, while the male acts as a guard for a certain period to protect the chick. This protection period lasts approximately three to four weeks.

The chicks leave the nest after an average of 75 days, having acquired adult-like plumage (fledging period), and then enter the juvenile/migratory period. During the post-breeding moulting period, individuals generally remain in the colony area or near colonies, and food intake decreases during this period; this process results in the renewal of adult plumage.

Conservation Status

The crested penguin (Eudyptes sclateri) was last assessed on 21 August 2020 and is listed as Endangered (EN) on the IUCN Red List; reasons include its limited distribution range and a significant decline in breeding pairs over the last few decades.

Population trends, particularly in censuses conducted from the 1970s to the 1990s and beyond on Antipodes and Bounty Islands, show a marked decline in the number of active nests in breeding colonies; this is a significant warning in terms of the ‘decline per generation’ criterion. Although the current population size is not precisely known, past estimates suggested hundreds of thousands of breeding pairs, whereas current estimates are well below these figures, indicating that the species is at risk in terms of population size criteria.