Hawaiian Goose Life History

Habitat

Hawaiian Geese are very adaptable in the habitats they use, ranging from sea level to alpine areas over 6,500 feet. They feed on both native and introduced plants, which allows them to use golf courses and pastures as well as native shrub-grasslands. On Kauai, where most Hawaiian Geese now occur, they primarily live year-round below 1,000 feet in pastures, golf courses, and other human-altered areas. On Hawaii and Maui, many Hawaiian Geese nest and forage in grassy shrublands or lava flows with limited vegetation. During the nonbreeding season, many geese on Hawaii occur in an area of Hawaii Volcanoes National Park where native shrubs such as mamaki are common in volcanic ash.

Food

Hawaiian Geese are plant eaters, feeding on the leaves, seeds, fruits, and flowers of grasses, herbs, and shrubs. They do not forage in water, instead focusing on terrestrial plants, both native and introduced. These geese graze on grasses and other plants on the ground, but also extend their necks and even climb into shrubs to reach hanging fruits. When pulling up plants, Hawaiian Geese eat only the succulent parts, discarding other parts that are less digestible.

Nesting

Nest Placement

Placed on the ground, typically under shrubs and trees. On Hawaii and Maui, these shrubs and trees are usually native species, but on Kauai, introduced species are more commonly used.

Nest Description

Females dig a shallow scrape in the ground, creating a round nest bowl that they first line with vegetation, and later, with downy feathers. They surround the bowl with an above-ground rim composed of soil, leaves, twigs, and feathers.

Nesting Facts

Behavior

Hawaiian Geese spend most of their time on the ground and have several adaptions for a terrestrial lifestyle. They stand upright on strong legs, allowing them to reach up for fruits, seeds, and foliage. They have less foot webbing than other geese, which together with long toes and large nails helps them walk over lava and other rugged terrain. Hawaiian Geese have small wings for their size and are weak fliers compared to Canada Geese. And while they can swim and use water for taking off and landing, they are adept at taking flight from, and landing on, the ground.

Hawaiian Geese are monogamous, forming lifelong pair bonds when they are a year old. Courtship displays and copulation are on the ground, rather than in water. Females select the nest site and build the nest, while males guard the nest from an elevated viewpoint. Hawaiian Geese lay very large eggs and have the longest incubation period of any geese—typically 30 days. Young geese leave the nest 1–2 days after hatching and can immediately feed themselves, but they stay with their parents until the start of the next breeding season. Pairs and families stay close together, but otherwise, Hawaiian Geese are less social than other geese. Flocks are usually smaller than 30 birds (perhaps due to small overall population sizes), and when birds do flock, unrelated individuals keep some distance between themselves.

Conservation

Hawaiian Geese nearly went extinct in the 20th century, with the wild population dropping to an estimated 30 individuals by 1957 as a result of habitat destruction, introduced predators, and historic hunting pressure. The U.S. government listed this goose as Endangered in 1967 and reclassified it as Threatened in 2019. The IUCN Red List of Threatened Species lists Hawaiian Goose’s conservation status as Near Threatened. The IUCN assessment notes that while Hawaiian Goose’s population is increasing, it remains small (an estimated 1,700–2,200 mature individuals) and occurs in a small number of sites in a small geographic area. Although the species was downlisted to Threatened in 2019, it still requires active human management—invasive predator control, habitat and vegetation management, and predator-proof fences for nesting birds—to sustain population growth.

The reintroduction of captive-raised Hawaiian Geese—more than 2,000 were released between 1960 and 1997—played a major role in the recovery of this species, but mongoose and other introduced predators killed many of the released birds. In 1982, 12 captive geese on Kauai, an island without a mongoose population, escaped and bred in the wild. In 1991, these birds were augmented with a planned release of additional birds. Without mongoose present, Hawaiian Geese have flourished on Kauai—over 60% of the global population now occurs on this one island.

Credits

Banko, P. C., J. M. Black, and W. E. Banko (2020). Hawaiian Goose (Branta sandvicensis), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.hawgoo.01

International Union for Conservation of Nature (2022). The IUCN Red List of Threatened Species. Version 2022-2. https://www.iucnredlist.org.

National Park Service. Nēnē, the Hawaiian Goose.

Sandoval, Cindy (2022). Hawai‘i's State Bird Recovering With Support From U.S. Fish and Wildlife Service Grants. U.S. Fish & Wildlife Service.

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