The nene, also known as the Hawaiian goose, is a species of goose endemic to the Hawaiian Islands. With an estimated population of just 2,500 individuals in the wild, the nene is Hawaii’s state bird and one of the world’s rarest geese.
Overview of the Nene Goose
The nene is a medium-sized goose, standing around 25 inches tall and weighing 4-7 pounds as an adult. Both sexes have similar plumage, with buff-colored feathers on the head, neck, and breast contrasting with black feathers on the face, crown, wings, and tail. The nene’s legs and feet are also black and its short bill is black with pale tomia (cutting edges).
Some key identifying features of the nene include:
- Small head and short, thick neck compared to other geese
- Partially webbed feet adapted for terrestrial living
- High-pitched, whistling call
The nene is endemic to the Hawaiian Islands, where it occupies a variety of habitats from coastal dunes to alpine grasslands and lava flows. Evolution in isolation has made the nene different from other geese in several respects. Unlike migratory geese, the nene does not undertake long seasonal movements. It has also adapted to utilize terrestrial foods and nest in the ground rather than migrate and rely on aquatic foods and habitats.
Taxonomy and Evolution
The nene is classified as follows:
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Anseriformes
Family: Anatidae
Genus: Branta
Species: B. sandvicensis
The specific name sandvicensis refers to the former name of the Hawaiian Islands, the Sandwich Islands, after the English explorer James Cook named them in 1778.
The nene belongs to the waterfowl family Anatidae, which includes ducks, geese, and swans. It is believed that ancestral nene populations originated from North America, descending from the Canada goose (Branta canadensis). Several million years ago, a few Canada geese likely arrived on the Hawaiian Islands, probably blown off course during migration. In the isolation of the remote Hawaiian Islands, these geese evolved into the distinct species known today as the nene.
Compared to its Canada goose ancestors, the nene displays a number of unique adaptations to the Hawaiian environment, including reduced webbing on its feet, an altered diet, and changes in breeding behavior and molting patterns. Without predators or the need to migrate long distances, the nene also evolved to be less wary, flighty, and aggressive than other geese.
Physical Description
The nene is a medium-sized goose, weighing 4-7 pounds as an adult, with males averaging slightly larger than females. Total length ranges from 21-27 inches and wingspan is up to 1.5 feet.
The nene’s plumage consists of buff-colored feathers on the head, neck, and breast. This contrasts with black feathers on the face, crown, back of the neck, wings, and tail. The buff chest feathers have variable dark spots and barring. The rump is white. The bill is short and stout, black with pale tomia (cutting edges). The eyes are dark brown. The legs and feet are long and black.
A unique feature of the nene is its partially webbed feet, an adaptation to terrestrial living. The feet have reduced webbing compared to other geese and expanded hind toes to improve walking ability. The middle front toes are the most webbed.
Male and female nene are similar in appearance, although males average 10-15% larger in size. Juveniles have a grayish plumage overall and lack the definitive black and buff coloration of adults. The adult plumage is acquired with the first complete molt at around one year old.
Distribution and Habitat
The nene is endemic to the Hawaiian Islands in the central Pacific Ocean. Scientists estimate that at least 25,000 nene once occupied all the Main Hawaiian Islands before human arrival, from Ni’ihau and Kaua’i in the northwest to Hawai’i Island in the southeast.
Today, wild nene populations exist on Hawai’i, Maui, Kaua’i, and Moloka’i. Reintroduced populations have also been established on Oahu and Kauai. Total wild population is estimated at only 2,500 birds.
Nene adapt to a wide variety of habitats on the islands, including:
- Coastal dunes and beaches: nesting and raising young.
- Lowland grasslands and shrublands: feeding on grasses, sedges, native berries.
- High-elevation alpine grasslands and lava flows: breeding, feeding on lichens and montane vegetation.
- Montane cloud forests: utilize mossy forests for shelter, nesting, feeding.
This flexibility allows nene to utilize habitats from sea level to 8,200 feet in elevation. They tend to avoid dense wet forests. Nene descend to lower elevations in winter to avoid deep snow at higher elevations.
Diet and Feeding Behavior
The nene is primarily herbivorous, feeding on a wide variety of plant material. Their diet consists mainly of leaves, seeds, fruits, flowers, and roots of grasses, sedges, ferns, shrubs, and other native and introduced vegetation.
Important food plants include pili grass, flowering ryegrass, jungle rice, glandular pili, and various native and non-native berries including blackberry, thimbleberry, and strawberry guava. On high lava flows with little vegetation, nene rely heavily on scant mosses and lichens for food. They also occasionally graze on aquatic vegetation near ponds and coastal shores.
Nene feed by walking along the ground and grazing, pulling and plucking vegetation with their small bills. They do not exhibit the tearing and digging feeding behaviors typical of many geese. Nene are non-migratory but may locally migrate seasonally between elevations to utilize the best food sources.
Nene chicks are precocial and able to feed themselves soon after hatching, but are brooded under the wings of parents for warmth and protection. Adults and young often feed together in small flocks or family groups.
Unique Adaptations
Evolution in isolation in the remote Hawaiian Islands has shaped a number of distinctive traits and behaviors in the nene:
- Flightlessness – Nene wings are 15-20% smaller than their Canada goose ancestors. Nene rarely fly and some populations are essentially flightless. This correlates with reduced predation.
- Non-migratory – Without needing to migrate long distances, the nene’s pectoral muscles and heart mass are reduced compared to other geese. Their wing bones are more fragile as well.
- Terrestrial living – The nene’s partially webbed feet provide better walking ability in the Hawaiian Islands’ rugged and dry lava landscapes.
- Generalized diet – With a diverse plant diet and ability to live across elevations, nene are less dependent on specific food resources.
- Tame and curious – Without mainland predators, nene did not evolve a strong wariness of other animals and can be very approachable. Parents aggressively defend young though.
- Unique molt – Nene undergo a simultaneous wing molt once per year, leaving them flightless for 4-6 weeks. Other geese molt gradually to avoid this.
- Nesting habits – Unlike most geese, nene nest in concealed locations like lava tubes and vegetated depressions. Nesting in the open makes them more vulnerable to predators.
Breeding and Life Cycle
The nene is a highly social goose yet also exhibits strong long-term pair bonds between breeding adults. Breeding pairs undertake elaborate courtship displays, especially during the autumn breeding season. These include honking calls, head bobbing and posturing, and ritualized aggression between competing males.
Nesting starts in October, with pairs building a well-concealed nest on the ground lined with feathers and vegetation. Unlike most geese, the nene does not nest in the open and seeks cover in depressions, lava tubes, rock crevices, or under dense bushes. The female lays 2-5 eggs that hatch after 29-32 days of incubation.
Nene chicks are precocial, able to feed themselves soon after hatching. Both parents protect and brood the young, especially for the first 2 weeks until they can fully thermoregulate. Parents are very defensive of young and will hiss, chase, and even attack potential threats.
The chicks fledge at 10-12 weeks old but stay with their parents as a family group for up to a year, learning feeding and social behaviors. Juveniles start acquiring adult plumage around 6 months old.
Young nene start breeding at one to two years old and typically form long-term pair bonds with a single mate. The oldest known nene in the wild survived at least 22 years. Major threats to survival include introduced predators, habitat loss, vehicular collisions, and disease outbreaks.
Conservation Status and Threats
Due to severe population declines primarily caused by introduced predators and habitat alteration, the nene is listed as an endangered species under both Hawaiian state law and the U.S. Endangered Species Act.
Current population is estimated at only 2,500 individuals in the wild, about 10% of historical numbers. Major threats to survival include:
- Predation: Mongooses, feral cats, dogs, pigs, and rats consume eggs and young and attack nesting adult nene.
- Habitat degradation: Invasive plant species, deforestation, urbanization, habitat fragmentation.
- Vehicular collisions: Nene feeding along roads are prone to strikes by vehicles.
- Overgrazing: Impacts from introduced large mammals like goats and deer.
- Disease: Avian botulism and avian cholera outbreaks have decimated populations. West Nile virus is an emerging threat.
- Inbreeding depression: Small, fragmented populations have low genetic diversity.
Intensive conservation actions by wildlife agencies and nonprofits aim to boost nene populations. These include captive breeding programs, predator control, habitat protection and restoration, raising public awareness, and wing-tagging studies to understand nene movements and survival. If conservation efforts continue, scientists estimate nene populations could potentially recover to over 10,000 birds within decades.
Interesting Facts about Nene
The unique Hawaiian goose displays a number of unusual traits and behaviors compared to other geese:
- Nene mate for life, with pairs often staying together for over 15 years. Both parents raise young together.
- Their partially webbed feet allow them to walk over rough lava flows, unlike most waterfowl.
- Nene undergo an annual simultaneous wing molt, leaving them flightless for 1-2 months each summer.
- They have evolved to be quite tame and approachable due to lack of mainland predators.
- Nene nest in concealed locations like lava tubes, unlike other geese that nest in the open.
- With no migration, nene pectoral muscles are much smaller than other geese. Their hearts are also smaller.
- Hawaii’s isolation allowed nene to occupy both aquatic and terrestrial habitats, unlike mainland geese more adapted for water.
- Nene evolved a diverse plant diet including many native Hawaiian fruits and berries unavailable to ancestral Canada geese.
- Hawaii’s state wildlife agency conducts annual nene breeding counts during the peak nesting season each fall.
- There are estimated to be over 1,300 nene in managed breeding programs and wildlife refuges across Hawaii.
Frequently Asked Questions about Nene
Q: What does the nene look like?
The nene is a medium-sized goose with buff-colored plumage on the head, neck, and breast contrasting with black feathers on the face, crown, wings, and tail. They have partially webbed feet and a short black bill.
Q: Why is the nene endangered?
The main reasons nene populations declined are predation by introduced species like feral cats and pigs, loss of habitat to development and invasive plants, vehicle collisions, and disease outbreaks. There are now only about 2,500 birds left in the wild.
Q: Where do nene live?
Nene are endemic to Hawaii, found only on the islands of Maui, Kauai, Hawaii, Molokai, and Oahu thanks to reintroduction efforts. They can inhabit elevations from sea level to over 8,000 feet.
Q: What do nene eat?
Nene are herbivores that graze mainly on grasses, sedges, ferns, leaves, seeds, berries, and flowers. Their diverse plant diet includes many native Hawaiian plant species.
Q: How do nene nest?
Unlike most geese, nene nest on the ground in concealed locations like lava tubes and dense vegetation rather than exposed areas. The female lays 2-5 eggs in a nest lined with plant material.
Q: How long do nene live?
The oldest known nene in the wild was at least 22 years old. In captivity, nene may live over 30 years. They reach breeding age at 1-2 years old and form lifelong pair bonds.
Q: Why can’t nene fly well?
As an island species without mainland predators, nene did not need strong flying abilities and their wings evolved to be smaller. They are essentially flightless on some islands.
Q: Are nene territorial?
Nene pairs aggressively defend small breeding and nesting territories but otherwise are social and tolerant of other birds outside the breeding season. Groups may congregate at good food sources.
Q: How many nene are left in the world?
The total world population of wild nene is estimated to be only around 2,500 birds as of 2022. There are also over 1,300 nene in managed captive breeding colonies and wildlife refuges.
Conclusion
The unique nene goose is a highly endangered Hawaiian endemic facing threats from invasive species and habitat loss. As Hawaii’s state bird, the nene represents an important cultural symbol and efforts to preserve it also help protect other native Hawaiian plants and animals. With intensive conservation actions, scientists are hopeful nene populations can recover to sustainable levels and these unique island geese can thrive once again in their island home.