Anianiau (Hemignathus parvus)

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Anianiau standing on leaf, feeding on native kanawao flower
IUCN Red List species status – Vulnerable VULNERABLE

Top facts

  • The anianiau is the smallest of the Hawaiian honeycreeper species.
  • The anianiau has quite uniform yellow plumage, with males being brighter in colour than females.
  • Found only on the Hawaiian island of Kaua'i, the anianiau is restricted to upland forests where disease-carrying mosquitoes are scarce.
  • As well as eating arthropods, the anianiau drinks nectar from flowers, rolling its brush-tipped tongue into a tube to reach it.
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Anianiau fact file

Anianiau description

KingdomAnimalia
PhylumChordata
ClassAves
OrderPasseriformes
FamilyFringillidae
GenusHemignathus (1)

A strikingly yellow bird, the anianiau (Hemignathus parvus) is the smallest of the Hawaiian honeycreepers (2) (4) (5). The male anianiau has distinctively uniform colouring, with beautiful yellow plumage on its back, head and chest. The only exceptions to this are the feathers on its wings and on its tail, which are dark with broad yellow edging (3). The female and juvenile of this species are similar in appearance to the male, but are duller in colour (2) (3) (4) (5). The female anianiau is also slightly smaller than the male (2).

The bill of the anianiau is short and slightly curved (2) (3), although the common name of this species comes from a Hawaiian word meaning ‘straight-beaked’ (2) (6). The bill is pale brown to yellowish, as are the anianiau’s legs and feet. The scientific name of the anianiau, parvus, comes from the Latin for ‘small’, in reference to this bird’s tiny size (2).

The anianiau typically calls with a two-note ‘tew-weet’, with the second note being higher in pitch than the first. The male anianiau also sings with a high-pitched, sweet-sounding trill of repeated notes, described as ‘weesee-weesee-weesee­’ or ‘weesity-weesity-weesity(2) (3).

Also known as
'anianiau, lesser 'amakihi.
Synonyms
Himatione parva, Magumma parva, Viridonia parva.
Size
Length: 10 cm (2) (3)
Weight
9 - 10 g (2) (4)
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Anianiau biology

The anianiau feeds largely on nectar from the flowers of native and non-native trees (2) (4) (5), rolling its brush-tipped tongue into a tube to reach this sugar-rich food. This bird may also use its bill to pierce flowers at the base and take the nectar (2). In addition, the anianiau gleans arthropods such as caterpillars and spiders from trees and other foliage (2) (3) (4) (5).

Constantly on the move, the anianiau spends most of its time in the outer foliage of the trees, rarely visiting the trunk or larger branches and very rarely, if ever, coming to the ground (2) (4). It may sometimes forage in small flocks, particularly at rich nectar sources (2) (5).

The male anianiau defends the breeding territory, which can be as small as nine metres in diameter (2) (5), and sings from dawn until dusk during the breeding season (2). This species is socially monogamous, and its breeding season is from February to June. Both the male and female anianiau construct the open-cup nest from plant fibres such as leaves, twigs, grass and bark. They spend four to five days building the outer lining, and two to three days making a fleecy, warm inner layer (2).

The female anianiau incubates the clutch of about 3 eggs for 14 days (2), and during this period the male forages for food, bringing it back to the nest for the female (2) (5). Both sexes look after the young (2) (4), which leave the nest about 18 days after hatching (2). This tiny bird has been known to live for nine and a half years in captivity (2).

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Anianiau range

Endemic to the Hawaiian island of Kaua'i (2) (3) (4) (5), the anianiau currently occupies only about 15 percent of its previous range. It is now restricted to higher elevation forests in the Kōke'e, Alaka'i, and Waimea regions of Kaua'i Island, at elevations of 600 metres and above (2) (4) (5). This species is presently uncommon to rare in lowland areas (3), although it may range below elevations of 100 metres in isolated valleys on the northwest coast of the island (2) (3).

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Anianiau habitat

This tiny bird inhabits montane rainforests on Kaua'i (2) (3) (7). This elevated forest includes native and introduced trees, including 'ōhi'a (Metrosideros polymorpha), koa (Acacia koa), 'ōlapa (Cheirodendron trigynum) and lapalapa (Cheirodendron platyphyllum) (2) (4) (5).The anianiau typically builds its nest in the 'ōhi'a tree (3).

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Anianiau status

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

IUCN Red List species status – Vulnerable

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Anianiau threats

The degradation of native forest on Kaua'i means a loss of habitat for the anianiau that threatens its continued existence on the island. The clearing of forest for timber, agriculture and urban development contributes to this, as does browsing by introduced species such as goats, while the spread of exotic plants is causing further habitat degradation (3) (4). Although the anianiau is relatively tolerant of habitat disturbance, it is more common in undisturbed native forest (2) (3) (5).

Another major threat to the anianiau is the introduced southern house mosquito, Culex quinquefasciatus. This mosquito is a vector for diseases that affect the anianiau, particularly avian pox and avian malaria. As a result, the anianiau is now largely confined to upland forests where there are fewer mosquitoes (4) (7). However, the increase in temperature expected as a result of climate change is likely to cause a corresponding increase in the range of the mosquito on the island, spreading these diseases to higher elevations (3) (4).

Other introduced species also have negative effects on the anianiau. Feral pigs exacerbate the spread of disease by creating wallows in which mosquitoes can breed, and also destroy understorey plants as well as spreading the seeds of invasive plants (2) (3) (4). Introduced predators such as cats, barn owls and rats are another very real threat to the survival of the anianiau (2) (3) (4) (5), and introduced birds can serve as reservoirs of disease (2) (4).

The anianiau also suffers from competition for food resources with introduced wasps and ants, and particularly with the Japanese white-eye (Zosterops japonicus) (2) (3) (5). In other native Hawaiian birds, this competition causes lower body mass that makes juveniles less able to resist disease. The lack of nutrition in early life also causes these birds to have stunted bill growth, which impairs their foraging ability (8).

Its restricted distribution makes the anianiau more vulnerable to any catastrophic events, such as hurricanes (3) (4). However, since its drastic reduction after the destruction of forest areas by Hurricane Iniki in 1992, the anianiau population seems to be on the increase (2), and this species is currently thought to be stable in its remaining habitat (2) (4) (5).

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Anianiau conservation

There are no conservation programmes in place that specifically target the anianiau. However, there are protected areas on Kaua'i Island that preserve its habitat, including the Alaka'i Wilderness Preserve and Kôke'e State Park (2) (3). There are plans to fence part of the Alaka'i Wilderness Preserve and remove feral animals from the area (3).

An existing programme that promotes awareness and preservation of the island’s native birds is the Kaua'i Forest Bird Recovery Project. Although the anianiau is not the project’s primary focus, it will benefit from research into factors threatening other native birds in this habitat (4). The Kaua'i Watershed Alliance also targets the maintenance of healthy elevated forest areas. The control of exotic weeds and of ungulates such as feral pigs is a major part of its ongoing activity, which will benefit the anianiau (9).

Proposed conservation measures for this small bird include surveys to monitor its population trends, continued protection and management of its habitat, control of non-native species, and further research into its biology (2) (3) (5). Investigations are also underway to better understand the threat posed to the anianiau and other Hawaiian birds by disease (7), and if disease-resistant individuals can be identified it may be possible to breed them in captivity or reintroduce them to parts of this species’ former range (2) (3).

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

Find out more about the anianiau and its conservation:

Find out more about conservation on Kaua'i:

More information on conservation in Hawaii:

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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

This species information was authored as part of the ARKive and Universities Scheme.
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Glossary

Arthropods
A major grouping of animals that includes crustaceans, insects and arachnids. All arthropods have paired jointed limbs and a hard external skeleton (exoskeleton).
Endemic
A species or taxonomic group that is only found in one particular country or geographic area.
Feral
Previously domesticated animals that have returned to a wild state.
Gleaning
The catching of prey by plucking it from or within foliage.
Incubate
To keep eggs warm so that development is possible.
Monogamous
Having only one mate during a breeding season, or throughout the breeding life of a pair.
Montane forest
Forest occurring in mountains.
Territory
An area occupied and defended by an animal, a pair of animals or a colony.
Ungulates
A general term for a mammal with hooves. Includes the artiodactyls or ‘even-toed ungulates’ (pigs, deer, sheep, antelopes and cattle) and perissodactyls or ‘odd-toed ungulates’ (horses, tapirs and rhinoceroses).
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References

  1. IUCN Red List (November, 2011)
    http://www.iucnredlist.org/
  2. Lepson, K.K. (1997) Anianiau (Hemignathus parvus). In: Poole, A. (Ed.) The Birds of North America Online. Cornell Lab of Ornithology, Ithaca. Available at:
    http://bna.birds.cornell.edu/bna/species/312/
  3. BirdLife International - Anianiau (November, 2011)
    http://www.birdlife.org/datazone/speciesfactsheet.php?id=8908
  4. Kaua'i Forest Bird Recovery Project (November, 2011)
    http://kauaiforestbirds.org/
  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/files/NAAT%20final%20CWCS/Full%20document%20Hawaii%20CWCS.pdf
  6. Pyle, R.L. and Pyle, P. (2009) 'Anianiau. In: The Birds of the Hawaiian Islands: Occurrence, History, Distribution, and Status. B.P. Bishop Museum, Honolulu, Hawaii. Available at:
    http://hbs.bishopmuseum.org/birds/rlp-monograph/pdfs/08-DREP/ANIA.pdf
  7. USGS (1999) Impacts of Introduced Avian Diseases on Native Honeycreepers. USGS Fact Sheet 012-99, USGS, Reston, Virginia. Available at:
    http://pubs.usgs.gov/fs/FS-012-99/pdf/fs-012-99.pdf
  8. Freed, L.A. and Cann, R.L. (2009) Negative effects of an introduced bird species on growth and survival in a native bird community. Current Biology, 19(20): 1736-1740.
  9. Kaua'i Watershed Alliance (November, 2011)
    http://hawp.org/partnerships/kauai-watershed/
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Image credit

Anianiau standing on leaf, feeding on native kanawao flower  
Anianiau standing on leaf, feeding on native kanawao flower

© Jack Jeffrey Photography

Jack Jeffrey
P.O. Box 40
Pepeekeo
Hawaii
96783
United States of America
Tel: +1 (808) 933 6915 (Ex28)
Fax: +1 (808) 933 6917
jjphoto@hawaii.rr.com
http://www.jackjeffreyphoto.com

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