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< >  Anas wyvilliana - Hawaiian duck (Click photographs/illustrations: full picture & further details)
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INFORMATION AVAILABLE

GENERAL & REFERENCES

EXTERNAL APPEARANCES

REPRODUCTION

BEHAVIOUR

NATURAL DIET

RANGE & HABITAT

CONSERVATION

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General and References

Alternative Names (Synonyms)

Koloa
Anas platyrhynchos wyvilliana

Names for newly-hatched

Duckling, downy.

Names for non-breeding males or other colour-phases

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References

Species Author

Debra Bourne

Major References

B1, B3, B5, B8, B19, B25, B26.

Aviculture references:
B7, B29, B30, B40, B94, B128.w1
D1, D8

Other References

B44.9.w1
W2
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TAXA Group (where information has been collated for an entire group on a modular basis)

Parent Group

Specific Needs Group referenced in Management Techniques

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Aviculture Information

Notes

General Information:
  • Dabbling Ducks are generally hardy, easy to maintain and easy to breed. Shelter may be required by some of the smaller species in winter. They should be provided with cover (including marginal pond cover) and loafing areas as well as water. A pen which is 50% water is suggested. The water may be shallow (i.e. no more than two feet deep is required), and muddy areas for dabbling in are also appreciated. These ducks are generally good in mixed collections, although the smaller and quieter species may be bullied. Territorial disputes between ducks of the same species may be avoided by keeping only one pair of each species in an enclosure, unless the area is very large. For a single pair of ducks a pen are of 50 to 100 square metres, depending on the size of duck, should be provided.
  • A diet based on wheat and pellets is suggested, with maintenance pellets changed to breeders pellets for the breeding season. Bread and greenfood are also appreciated. Grit should always be available, with soluble grit (e.g. oystershell grit) as a calcium source when breeding.
  • Most species are ground nesters and both close ground cover and ground level nest boxes should be provided. Hand-rearing is generally preferred, as these ducks are generally poor parents in captive conditions, particularly in enclosures shared with other waterfowl. These ducks are prone to hybridization, particularly with closely related species, which should be kept apart from one another.

(B7, B29, B30, B40, B94, B128.w1, D1)

Species-specific information:

  • Hawaiian ducks are not difficult to keep; cover and loafing areas should be provided as well as water.
  • These ducks are easy to breed. They usually lay from April to June, in close ground cover or ground-level nest boxes.
  • This duck readily hybridises with Anas laysanensis - Laysan duck. Should be kept separate from this species and other closely-related (mallard-type) species to avoid hybridisation.

(B29, B30, B94)

Aviornis UK Ringing Scheme recommended average closed ring size: J 9.0mm (D8).

Management Techniques

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External Appearance (Morphology)

Measurement & Weight

Length 44-49cm, 17-19 inches (B25).
Adult weight General --
Male Mean 670g (B25); mean 1.5 lbs. (B8).
Female Mean 573g (B25); mean 1.3 lbs. (B8).
Newly-hatched weight --
Growth rate --

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Head

Adult Bill Male Grey/olive, with black nail and culmen patch.
Variations (If present) Female: dusky, becoming orange near the tip.
Eyes (Iris) Male Brown.
Variations(If present) --
Juvenile Bill Dusky.
Eyes (Iris) Brown.

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Legs

Adult Male Orange, with dusky webs.
Variations (If present) Female: duller orange, with dusky webs.
Juvenile Orange, with dusky webs.

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Plumage

Adult Male Head and neck brown with dark speckling, N.B. individually variable green/black particularly on crown, narrow pale eyering. Breast deep chestnut-brown with darker markings, body warm brown with darker markings. Tertials dark grey, central tail feathers variably slightly upcurling and black, rump and upper tail-coverts black.

Wing has coverts and primaries brown, greater coverts white-tipped, secondaries iridescent green to blue with black subterminal band and white tips: speculum with narrow black and white boundaries.

Variations (If present) Female: Similar to female mallard. Head and neck pale with darker crest and hindneck, eyeline indistinct, breast reddish-brown, mottled. Body mottled warm brown. Wings as male.

Eclipse, and duller males in breeding season: Similar to female.

Juvenile Similar to female, but duller with markings on feathers less visible.

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Newly-hatched Characteristics

General: -- Upperparts olive-brown with buff-yellow markings, underparts buff-yellow. Brown eyeline and ear spot.
Bill: Grey.
Feet: Grey.

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Reproduction

Reproductive Season

Time of year Irregular: may lay all year but mainly March-June.
No. of Clutches --

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Nest placement and structure

On the ground, well hidden in vegetation.

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Egg clutches

No. of Eggs Average 8-10 (B8).
Range 6-13 (B8); 6-12 (B5).
Egg Description Greenish-white.

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Incubation

26-28 days (B5, B8).

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Hatching

Synchronous.

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Fledging

50-60 days (B8).

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Sexual Maturity

Males One year old.
Females One year old.

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Behaviour

Feeding Behaviour

Adults Dabbles while swimming or wading, also feeds on land while walking, on crops or pasture.
Newly-hatched --

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Parental Behaviour

Nest-building Solitary nests, or in loose groups. Built by female.
Incubation By female only.
Newly-hatched Tended by female only.
Juveniles

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Social Behaviour

Intra-specific Gregarious except while breeding. Found in sizeable groups in winter.
Inter-specific --

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Sexual Behaviour

Pair bonds formed between November and May.

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Predation in Wild

Particularly introduced mongooses, also dogs, cats and rats. Introduced bullfrogs also take ducklings.

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Activity Patterns

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Circadian --

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Natural Diet

Adults

Seeds of grasses, rice, molluscs, dragonfly larvae.

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Newly-hatched

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Range and Habitat

Distribution and Movement (Migration etc.)

Normal

Hawaiian islands: Kauai.

Sedentary.

Occasional and Accidental

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Introduced

Re-introduced to Hawaii and Oahu.

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Habitat

Any freshwater area – mountain streams, lowland marshes, ditches, wet fields, reservoirs, boggy forests.

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Conservation

Intraspecific variation

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Conservation Status

Wild Population -
(Importance)

Rare, low numbers (B1, B44.9.w1).

CITES listing --
Red-data book listing Vulnerable (W2).
Threats Habitat loss, hunting and introduce species. (B44.9.w1)

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Captive Populations

Relatively abundant in collections (B8).

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Trade

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