The Royal Penguin (Eudyptes schlegeli) is an endemic species that breeds only on Macquarie Island and the surrounding islets, distinguished from other yellow-crested penguins by its white face. The population size is currently estimated at approximately 850,000 breeding pairs. Historically, intensive hunting for oil production in the 19th and early 20th centuries led to significant losses. However, with the cessation of hunting, the population began to increase. Today, it is considered sensitive to changes in marine ecosystems due to its diet consisting of krill, small fish and squid. Due to the fact that its breeding area is limited to a single, restricted region, individual threats such as oil spills, climate change, or the re-emergence of invasive species have the potential to impact the population. For these reasons, the species is classified as ‘Least Concern’ (LC) on the IUCN Red List.

Morphological Characteristics and Systematic Position

Physical Description

The royal penguin (Eudyptes schlegeli) is approximately 65–75 cm tall, and adult individuals are estimated to weigh between 4–6 kg; males tend to be slightly larger. Its back is covered with dark black/blue-black feathers; its belly and sides are bright white. On its face, there is a ‘crest’ formed by yellow-orange feathers that merge along the forehead, and this characteristic feather pattern distinguishes it from other yellow-crested penguins. Around the eyes, areas of pink, exposed skin extending to the upper beak are observed, which may play a role in swimming and thermoregulation (affecting heat exchange through the regulation of blood flow). The wing bones are flattened and adapted for swimming, while the feathers are densely packed and coated with oil — these features provide both waterproofing and thermal insulation. There is no obvious visible dimorphism between the sexes; males may tend to be slightly larger in weight.

Taxonomy and Evolution

Molecular phylogenetic and palaeontological data regarding the taxonomic position of the royal penguin indicate that this species is part of the evolutionary radiation of the genus Eudyptes; The origin of the genus Eudyptes likely dates back to the late Miocene–early Pliocene periods (approximately 8–5 million years ago), during which speciation tendencies became apparent due to cooling marine conditions and the influence of oceanic frontiers (such as the Antarctic Polar Frontier and Subtropical Frontier). Molecular analyses reveal a genetic affinity between the macaroni penguin (Eudyptes chrysolophus) and the royal penguins in particular, suggesting that these two forms may have diverged from each other approximately 1.5 million years ago.

^{Royal penguin and its chick (Flickr)}

Ecology, Behaviour and Life Cycle

Habitat and Distribution

The royal penguin (Eudyptes schlegeli) establishes dense colonies only on Macquarie Island and nearby islets; colonies are located between coastal areas and sloping rocky surfaces, intermingled with the sea. During the breeding season, this species favours coastal areas that are advantageous in terms of distance from the nest to the sea and have low wave energy. In terms of feeding, king penguins mostly dive at depths of 6–32 m, but can dive deeper (e.g. to depths exceeding 100 m) when necessary. According to study data, their average diving depth is around 32.9 metres. The species carries out most of its foraging activities in the surrounding sea areas during the breeding season, particularly in the layers where the water column is active.

Nutritional Ecology

When examining the dietary profile of royal penguins, it is evident that their primary food source consists of euphausiid (krill) crustaceans; for example, studies conducted on Macquarie Island have determined that over 50% of the total food mass comprises the species Euphausia valentini and Thysanoessa gregaria. Additionally, myctophid fish (particularly Krefftichthys anderssoni) constitute a significant portion of the diet; these fish are typically in their juvenile stages. Other contributing sources include squid and other small cephalopods; however, their proportion is generally lower compared to krill and myctophid fish. Food selection varies seasonally: krill predominates during different stages of the breeding cycle, while the food range broadens somewhat during the chick-rearing period. In terms of foraging behaviour, king penguins target prey groups that roam the middle layers of the water column, preying predominantly on krill swarms and small fish shoals. This predation is usually carried out in groups; individuals attempt to drive their prey to the surface collectively by synchronised dives. This cooperative hunting strategy is particularly important for achieving high yields.

Reproductive Biology

The royal penguin (Eudyptes schlegeli) is a monogamous species; mates tend to return to the same breeding grounds each year. Males usually arrive at the breeding grounds in late September or early October, with females joining slightly later, and the egg-laying period peaks in October–November. Usually two eggs are laid; the interval between these eggs is 4–6 days, and in most cases the first egg is either small or disappears over time (obligate brood reduction). The eggs are incubated for 32–37 days; during this period, both parents take turns incubating. After hatching, chicks remain in the nest for the first 10–20 days, during which time the male parent in particular protects the chick. The chicks then join groups called “crèches” and leave the nest after approximately 5–6 weeks (≈ 35–42 days). After the breeding cycle, king penguins remain on land for several weeks during the moulting period and do not feed during this time; accumulated fat reserves are vital during this period.

Conservation Status

The species is listed as Least Concern (LC) on the IUCN Red List; this assessment was made in 2021 and is based on the assumption that the species maintains a large population and that the population trend is stable or possibly increasing. In terms of distribution criteria, although the royal penguin's breeding areas are limited to Macquarie Island and the surrounding small islets, no critical thresholds have been exceeded as there is currently no evidence of habitat shrinkage or widespread loss. Furthermore, according to scientific sources, it is not expected to fall into the threatened category in terms of population size; although the species has experienced excessive hunting pressure in the past, it does not currently show a significant population decline trend.