By st20113 
Introduction
The nene, known scientifically as Branta sandvicensis and commonly called the Hawaiian goose, holds the unique distinction of being both the official state bird of Hawaii and the rarest goose species on Earth. Evolved from ancestral Canada geese that reached the Hawaiian Islands millions of years ago — likely carried by storms or oceanic currents — the nene underwent dramatic transformations in its physiology and behaviour to become a fully terrestrial bird, uniquely adapted to Hawaii’s diverse landscapes from volcanic lava fields to upland grasslands. The species was brought back from fewer than 30 wild individuals in the 1950s through one of the most successful captive breeding programs in ornithological history.
Taxonomy
The nene belongs to the genus Branta, which comprises all dark-coloured goose species, and is placed within the family Anatidae alongside ducks, swans, and other geese. Molecular phylogenetic studies confirm that it evolved from an ancestral population of Canada geese (Branta canadensis) that colonized Hawaii, making it the closest living relative of that species. The two species can still interbreed in captivity, producing viable hybrid offspring. The nene was formally described by the German naturalist Johann Friedrich Gmelin in 1789. No subspecies are currently recognized, although some morphological variation exists between island populations.
Physical Characteristics
Adult nene geese stand approximately 56 to 71 centimetres tall and weigh between 1.7 and 3.1 kilograms, with males slightly larger than females. Their plumage is primarily greyish-brown on the body, contrasting sharply with the distinctive black head and neck. A creamy-buff to white band separates the black neck from the brown body, creating a visually striking appearance unique among the world’s goose species. Their legs and feet are dark grey to black, and critically, the feet are only partially webbed — unlike fully webbed waterfowl feet — an adaptation that facilitates efficient walking across rough lava terrain and grasslands rather than swimming. The bill is relatively short and black, adapted for grazing rather than the more specialized bills of other Branta geese.
Habitat
Nene geese inhabit a variety of open landscapes across the Hawaiian islands, including native shrubland, grassland, and volcanic lava fields, from sea level to elevations above 2,000 metres on the slopes of Mauna Kea and Mauna Loa. They show a particular preference for areas with short, palatable grass for grazing and gentle to moderate slopes suitable for nesting. Preferred habitats also include pastureland, golf courses, and other modified landscapes where introduced grazing animals have altered the vegetation structure. The reduction of native habitat has been partially offset by the bird’s adaptability to agricultural and semi-urban landscapes, though such environments carry increased risks from vehicle strikes and introduced predators.
Diet
The nene is primarily a grazer, feeding on the leaves, stems, seeds, and flowers of a wide variety of Hawaiian grasses and herbaceous plants. They also consume the leaves and fruits of introduced species including koa haole, lantana, and various berry-producing shrubs, which often constitute a significant portion of their diet in areas where native food plants have been displaced. During the breeding season, protein-rich foods including insects and small invertebrates become more important, particularly for growing goslings. The geese feed primarily during morning and late afternoon hours, resting in shaded areas during the heat of midday.
Reproduction
Nene geese form monogamous pair bonds that endure for life, with nesting from August through April. The female builds a shallow nest of grasses on gentle slopes, laying two to five eggs incubated for about 30 days. Goslings are precocial and remain with their parents for up to one year.
Conservation
The nene was saved from extinction through one of the most remarkable captive breeding achievements in ornithology. Starting with just 16 individuals captured from the wild in 1949 and 1950, breeding programmes across Hawaiian and international zoos produced thousands of goslings for release. Today’s wild population exceeds 3,000 individuals, yet the species remains classified as Vulnerable due to its extremely restricted range confined to a single archipelago and its vulnerability to introduced mammalian predators including mongoose, rats, and feral cats. Conservation efforts now focus on expanding habitat protection and reducing predation pressure on established populations.
Fun Facts
The nene is the world’s rarest goose species, with its entire global population descended from a founding population of just 16 birds. Unlike most other goose species, nene are non-migratory and spend their entire lives within the Hawaiian Islands. Their calls, often described as a nasal “nay-nay” and “ka-ha,” bear little resemblance to the honking calls of their Canada goose relatives, reflecting the significant vocal evolution that accompanied their island colonization. Interestingly, nene populations on the island of Kauai show slightly different morphology and behaviour from those on Hawaii and Maui, suggesting ongoing ecological differentiation.