The Fiordland penguin (Eudyptes pachyrhynchus) is a species with a limited distribution, breeding only on the western and southern coasts of New Zealand's South Island, and on Stewart and Solander Islands. It is strictly dependent on rocky caves and coastal shelters within dense forested areas. The breeding population, estimated at 5,000–10,000 pairs in the late 20th century, has now fallen below 3,000 pairs due to predation by marine mammals, fishing by-catch, fluctuations in marine food sources, disturbance from tourism, and habitat degradation. As a result of this continuous decline, the species has been listed as Vulnerable (VU) on the IUCN Red List, and measures to control predators and protect breeding areas are critical to the Fiordland penguin's survival.

Morphological Characteristics and Systematic Position

Physical Description

The Fiordland penguin (Eudyptes pachyrhynchus) is a medium-sized penguin, averaging 55–61 cm in height and reaching approximately 3.4–5 kg in weight during the pre-breeding period. Its plumage is dark blue-black on the back and head, while the belly is bright white. Bright yellow crest feathers extending from the beak to above the eye along both sides of the head characterize the species’ appearance Its beak is short and thick (slightly larger in males than in females), its feet are pinkish in colour, its flipper-like wings are strong enough to provide powerful propulsion in the water, and its feathers are dense and specialised for waterproofing and thermal insulation. There is no obvious sexual dimorphism in Fiordland penguins in terms of external appearance; that is, males and females look very similar in terms of plumage and colour, but males generally have a slightly larger beak, slightly longer legs, and slightly larger overall body measurements.

Taxonomy and Evolution

The Fiordland penguin within the genus Eudyptes is most closely related to its relatives the Macaroni (Eudyptes chrysolophus), Royal (E. schlegeli) and other ‘crested penguins’; fossil and molecular data indicate relatively recent divergences among the various members of the genus. For example, Bayesian total-evidence approaches suggest that the vast majority of modern penguin species diverged from one another within the last 2 million years; most species within Eudyptes were shaped by processes of dispersal into new habitats, isolation, and local adaptation in response to marine climate changes during the Pliocene and Pleistocene epochs. The fossil record contains examples of species such as Eudyptes calauina from the Pliocene period, indicating that crested penguins have long been diversified in the Southern Ocean and southern hemisphere coasts. Furthermore, studies on the genetic structure of modern populations indicate relatively high gene flow between colony boundaries among Fiordland penguins, suggesting that the species' distribution and population structure have persisted over the last thousand to several hundred years without major migrations or genetic divisions.

^{Fiordland Penguin (Flickr)}

Ecology, Behaviour and Life Cycle

Habitat and Distribution

Fiordland penguins (Eudyptes pachyrhynchus) establish colonies in sheltered breeding areas such as rocky shores, fjord mouths, and islands with dense forest cover; for example, the west coast of New Zealand's South Island, Stewart Island, and several nearby islands are the main areas where these colonies are found. During the breeding season, particularly during incubation and chick-rearing stages, they prefer to forage in waters within easy reach of their chicks; while some colonies use waters less than 500 metres inland from the shore, individuals have been observed venturing up to 80–100 km offshore into open sea and shelf areas. The dives of these penguins are mostly shallow to medium depth (e.g. some mid-fjord individuals ≤ 20 m, while individuals in outer fjord areas can dive deeper and longer), and are generally limited to dives lasting no more than a few minutes. Among marine food sources, cephalopods, krill, and crustaceans are prominent; fish species are less dominant.

Feeding Ecology

During the post-guard period after breeding, stomach content analyses of Fiordland penguins during the chick-feeding period revealed a significant proportion of cephalopods (up to 85% by weight), along with considerable amounts of crustaceans (such as krill) and very small fish larvae fragments. For example, in a study conducted in the Jackson's Bay and Martin's Bay colonies, fish only entered the diet at the small larval/post-hatch stage but accounted for a low proportion of the total mass.

Furthermore, penguins' prey preferences may vary across different regions: in some colonies, fish (especially larval fish) are dominant, while in others, cephalopods and krill are more important.

On the other hand, complex foraging behaviours such as ‘cooperative network patterns with synchronised dives in flocks’ or ‘tube-shaped fish school raids’ have not been clearly defined in the literature for Fiordland penguins. Current studies mostly focus on the feeding behaviour, prey composition, and diving depths of individual birds or those near colonies.

Reproductive Biology

The species is monogamous; pairs return to the same old nest in the same area (often the same cave or plant shelter) each year during the breeding season. Males usually arrive at the colonies in early July, with females joining a few weeks later; the female lays two pale greenish eggs between July and August. The eggs are incubated alternately by the parents for approximately 30–36 days. After hatching, the male protects the young in the nest for the first 2–3 weeks while the female focuses on bringing food; thereafter, both parents forage, and the young either remain alone or join loose “nursery” groups. When the chicks are approximately 75 days old, they moult (juvenile feathers) and leave the nest to take to the sea. Following the breeding season, adults enter a moulting period immediately after the chicks have fledged; the moulting process lasts approximately three weeks, during which time it is critical that they avoid entering the water, remain distant from food sources, and manage their fat reserves effectively.

Conservation Status

The species is classified as Vulnerable on the IUCN Red List as of 2020. During the assessment, it was emphasised that the population size is likely to decline significantly over three generations due to threats such as the relatively limited breeding range of the species, potential habitat fragmentation, and, in particular, declines in marine food resources. Current population estimates range between 2,500 and 3,000 breeding pairs, indicating that the number of mature individuals is in the order of several thousand. Although the estimated rate and magnitude of decline do not yet place the species in a higher threat category in terms of population trend criteria, the uncertainty and potential risks for the future warrant careful monitoring.