Iiwi (Vestiaria coccinea)

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Adult iiwi on branch
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Iiwi fact file

Iiwi description

KingdomAnimalia
PhylumChordata
ClassAves
OrderPasseriformes
FamilyFringillidae
GenusVestiaria (1)

The iiwi is one of the most spectacular of Hawaiian honeycreepers (2) (4) (5), a group that represents an impressive example of evolutionary radiation (6). Believed to have evolved from a single ancestor species, the honeycreepers spread throughout the Hawaiian Archipelago, and now show a remarkable variety of beak shapes, thought to be adaptations to different feeding habits (6) (7). A medium-sized honeycreeper, the adult iiwi is vivid scarlet in colour, with black wings and tail, a yellow eye ring, and a long, salmon-pink, distinctly downcurved beak (2) (3) (4) (5) (7). The wing linings are whitish, tinged scarlet, and there is a white patch at the top of the wings. The legs are pink, with brown toes (2) (3).

The male iiwi is larger than the female, but otherwise similar in appearance, while the juvenile is dull yellowish, with black streaks and sometimes a few reddish feathers, and has a dusky brown beak (2) (3) (4). The iiwi is similar in appearance to the ‘apapane (Himatione sanguinea), but the latter is distinguished by a white abdomen and undertail, a shorter, less curved, black beak, and deeper red plumage. The calls of the iiwi include a clear, distinct whistle and a flutelike ta-weet, ta-weet, ta-wee-ah, as well as a rather discordant song, ii-wii, which is produced by both sexes, and which gives the species its common name. The iiwi also often mimics other bird calls, and the wings produce a distinctive whirring noise during flight (2) (3).

Also known as
'i'iwi, scarlet Hawaiian honeycreeper, scarlet honeycreeper.
Synonyms
Certhia coccinea, Drepanis coccinea.
Size
Length: 15 cm (2) (3)
Weight
16 - 20 g (2)
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Iiwi biology

The iiwi’s distinctive beak appears to be adapted to exploit the nectar of the similarly-shaped flowers of lobelioid plants (Campanulaceae) (2) (4) (9), although, with a decline in these species, it now feeds more on the nectar of other plants such as ‘ohi’a (Metrosideros polymorpha) and the introduced banana poka (Passiflora mollissima). Individuals often undertake long flights over the forest in search of flowering trees, and the species is believed to be an important plant pollinator (2) (3) (4) (5). When feeding on a lobelioid flower, the iiwi uses a peculiar technique, perching above the flower before quickly swinging upside down, twisting the body, and probing the beak upwards, where it fits well into the long, downcurved flower (2) (9). A tubular tongue with a brushy tip aids in collecting the nectar. The iiwi will also obtain nectar by piercing or tearing a hole in the base of a flower, and supplements the diet with insects and spiders (2) (3) (4) (5). Interestingly, with a decline in lobelioids on Hawaii, the iiwi’s unique beak is thought to be undergoing an evolutionary change, gradually becoming shorter and less curved (6).

The iiwi has an extended breeding season, although peak breeding occurs between February and June, usually coinciding with the peak flowering of ‘ohi’a (2) (3) (4) (7) (10). The breeding pair remains together throughout the breeding season, defending a small territory around the nest, which is built by both sexes, usually in an ‘ohi’a tree, and is constructed from twigs, bark and lichens. Two eggs are normally laid, and are incubated by the female for around 14 days (2) (3) (4) (5). The young, which initially have a short, straight beak, leave the nest at about 21 to 22 days (2) (3) (4). Outside of the breeding season, the iiwis usually disperse from the breeding area, and may form small flocks, sometimes with other species (2) (3).

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Iiwi range

Once occurring on all the main islands of the Hawaiian Archipelago, the iiwi is now extinct on Lana’i Island, and only tiny populations, of fewer than 50 birds, remain on O’ahu and Moloka’i. The species’ main strongholds are now Hawai’i, Maui and Kaua’i islands, where it is still relatively common (2) (3) (4) (5) (8).

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Iiwi habitat

The iiwi was formerly found in native forests at all elevations, but forest clearance and the introduction of malaria-carrying mosquitoes has now mainly confined the species to wet or moderately wet forest above 1,250 metres, with reduced numbers occurring at lower elevations (2) (3) (4) (5) (8). It may also use dry forest, but does not often breed in this habitat (2) (4).

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Iiwi status

The iiwi is classified as Vulnerable (VU) on the IUCN Red List (1).

IUCN Red List species status – Vulnerable

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Iiwi threats

The native birds of Hawaii are facing a major extinction crisis, with many species already having gone extinct (2) (11). Once collected by native Hawaiians to make feather capes (2) (5) (12), the iiwi, like many other Hawaiian species, is now under threat from a combination of habitat loss, competition with and predation by introduced species, and disease (2) (4) (5) (8) (12). In particular, the iiwi is known to be highly susceptible to avian pox and avian malaria, introduced by humans with cage birds, and transmitted by introduced mosquitoes (2) (4) (5) (8) (11). The presence of malaria-carrying mosquitoes at low elevations has largely restricted the iiwi to higher elevations, but the species’ wide-ranging habits put it at risk of contracting malaria when moving to lower areas to feed, and the possible introduction of cold-tolerant mosquitoes, together with global warming, may allow malaria to spread to higher levels, which could prove disastrous to the iiwi. Although the iiwi is still relatively abundant, and was formerly one of the most common forest birds in Hawaii, the species is believed to be undergoing a continuing decline in both numbers and range, with the tiny populations on O’ahu and Moloka’i being at particular risk (2) (4) (5) (8) (12).

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Iiwi conservation

Conservation efforts for the iiwi are focused mainly on habitat restoration and disease control. A number of protected areas have been established in the native highland forests, and many are fenced to exclude or control introduced species such as goats, deer and pigs, which may damage the forest understorey and create breeding sites for mosquitoes. Efforts have also been underway to eliminate introduced mammalian predators, to control alien plants, and to restore native forest (2) (4) (5) (12), and the iiwi is also likely to benefit from a range of conservation actions aimed at other, more endangered forest birds (4) (5). Continued population monitoring will also be needed, along with efforts to control malaria and avian pox (2) (5) (8), and further research into the iiwi’s reproductive biology, together with the identification of disease-resistant individuals, may allow a captive breeding programme to be developed to aid the recovery of this striking native bird (2) (5).

View information on this species at the UNEP World Conservation Monitoring Centre.
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Find out more

To find out more about Hawaiian honeycreepers and about conservation in Hawaii, see:

 For more information on this and other bird species please see:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Incubate
To keep eggs warm so that development is possible.
Lichen
A composite organism made up of a fungus in a co-operative partnership with an alga. Owing to this partnership, lichens can thrive in harsh environments such as mountaintops and polar regions. Characteristically forms a crustlike or branching growth on rocks or tree trunks.
Pollinator
An animal that in the act of visiting a plant’s flowers transfers pollen grains from the stamen (male part of a flower) to the stigma (female part of a flower) of a flowering plant. This usually leads to fertilisation, the development of seeds and, eventually, a new plant.
Territory
An area occupied and defended by an animal, a pair of animals or a colony.
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References

  1. IUCN Red List (December, 2009)
    http://www.iucnredlist.org
  2. Fancy, S.G. and Ralph, C.J. (1998) Iiwi (Vestiaria coccinea). In: Poole, A. (Ed.) The Birds of North America Online. Cornell Lab of Ornithology, Ithaca. Available at:
    http://bna.birds.cornell.edu/bna/species/327/
  3. Pratt, H.D. (2005) The Hawaiian Honeycreepers: Drepanidinae. Oxford University Press, Oxford.
  4. National Audubon Society - Iiwi (December, 2009)
    http://audubon2.org/watchlist/viewSpecies.jsp?id=108
  5. Mitchell, C., Ogura, C., Meadows, D., Kane, A., Strommer, L., Fretz, S., Leonard, D. and McClung, A. (2005) Hawaii's Comprehensive Wildlife Conservation Strategy. Department of Land and Natural Resources, Honolulu, Hawai’i. Available at:
    http://www.state.hi.us/dlnr/dofaw/cwcs/index.html
  6. Smith, T.B., Freed, L.A., Lepson, J.K. and Carothers, J.H. (1995) Evolutionary consequences of extinctions in populations of a Hawaiian honeycreeper. Conservation Biology, 9: 107-113.
  7. Burnie, D. (2001) Animal. Dorling Kindersley, London.
  8. BirdLife International (December, 2009)
    http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=8921&m=0
  9. Spieth, H.T. (1966) Hawaiian honeycreeper, Vestiaria coccinea (Forster), feeding on lobeliad flowers, Clermontia arborescens (Mann) Hillbr. The American Naturalist, 100(914): 470-473.
  10. Ralph, C.J. and Fancy, S.G. (1994) Timing of breeding and molting in six species of Hawaiian honeycreepers. The Condor, 96: 151-161.
  11. Atkinson, C.T., Woods, K.L., Dusek, R.J., Sileo, L.S. and Iko, W.M. (1995) Wildlife disease and conservation in Hawaii: pathogenicity of avian malaria (Plasmodium relictum) in experimentally infected iiwi (Vestiaria coccinea). Parasitology, 111: S59-S69.
  12. The Nature Conservancy: Species Spotlight - 'I'iwi (Vestiaria coccinea) (December, 2009)
    http://www.nature.org/
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Image credit

Adult iiwi on branch  
Adult iiwi on branch

© Bill Coster / www.ardea.com

Ardea wildlife pets environment
59 Tranquil Vale
London
SE3 0BS
United Kingdom
Tel: +44 (0) 208 318 1401
ardea@ardea.co.uk
http://www.ardea.com

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