Branta sandvicensis

Geographic Range

The Hawaiian Goose, or nene, is endemic to the Hawaiian Islands.

• Biogeographic Regions
• pacific ocean pacific ocean
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

Nenes inhabit a variety of habitats, including grasslands, scrub forests, and sparsely vegetated volcanic slopes.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• scrub forest scrub forest
• mountains mountains

Physical Description

Adult nenes are either sepia or dark brown, with no difference in plumage between males and females. The face and crown are black, while the cheeks are cream-colored and the neck is buff with black streaks. The body is brown to grey, the wings are brown to gray, with white tips and the bottom side of the tail is black. The eyes, beak, and feet are black as well. Nenes have longer legs and less toe webbing than other geese, adaptations which aid walking on lava flows.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Nenes form life-long pair bonds. The male attempts to court the female by stiffly walking in front of her and showing her the white area under his tail. After the female has accepted the male, the two engage in a triumph ceremony in which the male aggressively pushes away rivals and then calls loudly. This is followed by calling into each other's ears. The display before copulation is comparable to other geese, except done on land instead of water. The head and neck are mutually dipped onto the ground, more and more synchronously. Finally the female becomes ready and the male mounts the female. Afterwards, the male raises his wings, pulls his mate's head back and touches her nape with his beak. This is followed by simultaneous calling by both birds, followed by the female flapping its wings and the male strutting.

• Mating System
• monogamous monogamous

Nenes have an extended breeding season ranging from August through April. However, the majority of nesting occurs between the months of October and March, and eggs are usually laid during the winter months between October and January. Nesting occurs on the ground in areas of dense vegetation. Nests are lined with plants and soft down. The female incubates and the male guards the female on the nest. Clutches consist of between 1 and 5 eggs, with an average of 3. Chicks are precocial, stop following parents within one year, and are sexually mature within 2 to 3 years.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

The female selects the nesting site, usually near her own natal site. Females dig a shallow scrape, usually under a bush or tree, and line the scrape with vegetation. Males rarely contribute to nest building. Females incubate the eggs, while the male guards her, though not constantly. The female spends roughly four hours of each day away from the nest, when she eats and rests. During hatching, the female spends more time on the nest, and stays on top of the young until their down dries. The young do not need to be fed by parents. Young readily forage within the first day. However, they remain close to their parents until roughly one year old.

• Parental Investment
• precocial precocial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • male
    • female
• pre-weaning/fledging
  • protecting
    • male
    • female
• pre-independence
  • protecting
    • male
    • female

Lifespan/Longevity

Annual mortality varies greatly from study to study, depending on whether the animal is wild or in captivity, locality, elevation, etc. The range is from 0 to 87% annual mortality, with slightly lower mortality rates for males than females. In the wild the main causes of mortality include exposure (from low temperatures in high nesting locations), predation (from several indigenous and introduced raptor species, as well as rats, pigs, dogs and mongoose), competition with other species (due to an overlap in diet with game birds and grazing mammals), and starvation or dehydration due to drought. In captivity, 84% of deaths resulted from parasites and diseases while the remaining 16% resulted from trauma. Males die evenly throughout the year. Female mortality occurs mainly in the breeding season when they are most vulnerable to exposure, trauma, and stress from egg laying and predation.

Behavior

Having longer and stronger legs, as well as less webbed feet than other geese, Nenes walk and run very swiftly on volcanic lava flows. Alternatively, since their wings are 16% smaller than their closest relative, the Canada Geese, they are not the best fliers. However, they can fly from island to island, usually taking off from land. They can also swim, usually in ponds and lakes. Similar to other water fowl, they also use their beak to spread oil from their oil gland along their feathers for water proofing.

Nenes are diurnal and sleep on the ground with feet beneath their bodies. The most tight nit social unit is the immediate family (mating pair and children). Nenes also live in flocks of up to 30 birds, some of which are more loosely constructed than others. Nesting ranges from as close as 45 meters to very far away. Dominance ranks come from the size of the family unit. Large families are dominant to small ones which are dominant to pairs which are dominant to individuals. Males defend the territory immediately surrounding nests and families from other Nenes.

Threat displays are numerous. The most common display is the bent-neck threat, which includes facing rivals with head and neck pointed downward, while the neck feathers vibrate. The most intense display is the forward threat, in which neck feathers are erect, the mouth is open and the bird is calling loudly, and the head and neck are up facing the opponent. This is often followed by charging of one bird towards another, in which case the subordinate usually runs off. Physical confrontation rarely occurs, and involve grabbing the neck of an opponent with one's beak, pulling, and beating the opponent with the wing.

• Key Behaviors
• cursorial
• terricolous
• flies
• natatorial natatorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• daily torpor
• social social
• dominance hierarchies dominance hierarchies

Home Range

Nene home ranges are roughly 200 square kilometers in size.

Communication and Perception

Other than threat and mating displays and sounds described previously, vocalizations are used to communicate with family members, solidify territory, send alarm calls, and threaten predators. Nenes also murmur when foraging as a way of maintaining foraging distance between family members. Chicks can send pleasure calls, distress calls, sleepy calls and greeting calls. Calls are louder during and close to breeding season.

In addition to auditory cues, vision is key in foraging and recognizing family members, predators, and opponents.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic

• Other Communication Modes
• duets duets

• Perception Channels
• visual visual
• ultraviolet
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Nenes are herbivores and forage solely on land. They eat leaves, grasses, flowers, berries, flowers, and seeds. Nenes usually eat the more nutrient rich bottom part of grasses, and grab and pull food with their beaks. Several important grasses on the Hawaiian islands that are eaten by nenes include Digitaria violascens , Andropogon virginicus , Sporobolus africanus , Carex wahuensis and some others.

• Primary Diet
• herbivore herbivore
  • folivore folivore

• Plant Foods
• leaves
• seeds, grains, and nuts
• fruit
• flowers

Predation

Males defend their brood and nest most often, while females also engage in defense sometimes. Threat displays such as the bent neck and forward threat are used to scare off predators. When defending themselves from aerial attack, nenes produce alarm calls, huddle in groups and spread wings, or they simply fly away. Chicks usually hide behind parents, leaving defense to them.

• Anti-predator Adaptations
• aposematic aposematic

Ecosystem Roles

Nenes are important at spreading seeds for many of the plants on which they feed. They are also important food sources for many of the predators mentioned in the previous predation section.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Nenes are the state bird of Hawaii and are thus a state symbol.

• Positive Impacts
• ecotourism ecotourism

Economic Importance for Humans: Negative

Since they fly low, nenes often collide with fences and automobiles. Otherwise, there are no known adverse effects of nens on humans.

Conservation Status

Early Hawaiian settlers used nenes as a food source and hunted the birds to near extinction. In 1907, a hunting ban was placed on these birds, but still approached extinction by 1940 due to predation by introduced species as well as degradation of habitat and other human related destruction. In 1957, nenes were named the state bird in Hawaii and efforts to rescue the almost extinct population, including breeding in captivity and protecting nesting areas began. Though early programs for reintroducing birds into the wild failed, later ones have been very successful and the wild nene population is recovering at around 800 individuals. Currently the greatest threat to nenes is predation of eggs by introduced Indian mongooses ( Herpestes javanicus ).

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Ali Batouli (author), Stanford University, Terry Root (editor, instructor), Stanford University.

References

Banko, P., J. Black, W. Banko. 1999. Hawaiian Goose (Nene) (Branta sandvicensis). Pp. 434 in The Birds of North America , Vol. 434. Philadelphia, PA: The Birds of North America, Inc.. Accessed May 15, 2007 at http://bna.birds.cornell.edu/BNA/account/Hawaiian_Goose/ .

National Audubon Society, 2002. "Hawaiian Goose (Branta sandvicensis)" (On-line). Audubon. Accessed May 15, 2007 at http://audubon2.org/webapp/watchlist/viewSpecies.jsp?id=100 .

US Fish and Wildlife Service. Nene or Hawaiian Goose. USFWS 2004. Portland, OR: US Fish and Wildlife Service. 2005. Accessed May 15, 2007 at http://72.14.253.104/search?q=cache:wKjqX5JnkEwJ:www.state.hi.us/dlnr/dofaw/cwcs/files/NAAT%2520final%2520CWCS/Chapters/Terrestrial%2520Fact%2520Sheets/Waterbirds/Nene%2520NAAT%2520final%2520!.pdf+hawaiian+goose+seeds&hl=en&ct=clnk&cd=4&gl=us .