Christmas imperial-pigeon (Ducula whartoni)
|Also known as:||Christmas imperial pigeon, Christmas Island imperial pigeon|
|Size||Head-body length: 42 - 45 cm (2)|
|Weight||450 - 700 g (2)|
Classified as Near Threatened (NT) on the IUCN Red List (1).
With dark purple and green, iridescent plumage, the Christmas imperial-pigeon can be seen perched conspicuously amongst the foliage of the Christmas Island rainforest. A mid-sized pigeon, with a distinctive bronzy green neck, the striking orange irises contrast sharply with a dark purplish grey head and a black bill. The underparts are dark sooty grey, with chestnut undertail-coverts, reddish brown legs and feet, and grey under the wings (2). In common with most pigeons, the sexes are very similar, but juveniles have a duller plumage, particularly around the chin and forehead, with darker and browner feathers on the underparts, and grey-brown legs (2) (3).
The Christmas imperial-pigeon is endemic to Christmas Island in the Indian Ocean. The species was unsuccessfully introduced to the Cocos-Keeling Islands at the end of the 19thcentury (3).
The Christmas imperial-pigeon is found in broadleaved rainforest. It is particularly abundant in plateau primary evergreen forest, and to a lesser extent, in secondary re-growth dominated by the introduced Japanese cherry (Muntingia calabura) (4). It may also be found in coastal forest when food trees are in fruit (2).
Foraging amongst the forest canopy for ripe fruits, the frugivorous Christmas imperial-pigeon will also eat buds and leaves, occasionally congregating in large groups on trees where food is abundant (2). The bird’s gizzard is adapted to strip off fruit’s pulp, leaving the seed intact, and making the Christmas imperial-pigeon an important seed disperser on the island. Like other pigeons, the Christmas imperial-pigeon is monogamous, mating with the same partner each season. The elaborate iridescent plumage may be used in courtship displays, which reinforce the bond between partners (5). Breeding takes place between August and February, with nests of loosely arranged twigs, constructed in the crown of large trees, often in loose colonies. In common with other tropical fruit eating pigeons, a single egg is laid. When hatched the young chick is naked, with feathers appearing after four to five days, and the chick fledging several weeks later (2).
Restricted to just a single island, the population of the Christmas imperial-pigeon is extremely small, with around 1,000 breeding individuals (3). Due to the destruction of a third of its habitat from phosphorous mining, and the introduction of the invasive ant species, Anoploepis gracilipes, which preys on nestlings and farms scale insects that cause canopy die-back, the Christmas imperial-pigeon received a Critically Endangered status on the IUCN Red List of Threatened Species in 2000 (4). However, the successful control of A. gracilipes using toxic bait between 2000 and 2006, eradicated the ant from around 95 percent of its former range, allowing the Christmas imperial-pigeon population to stabilise. The species also benefited from the introduction of the Japanese cherry, as it grows in areas that were formerly mined, thus increasing the area of suitable habitat (2) (3). Consequently, the species’ status has since been downgraded to Near Threatened (3).
Unfortunately, the A. gracilipes population has now partially recovered, and continues to threaten the Christmas imperial-pigeon, while plans for further mining have been proposed, within the species’ range (3). Other threats that may have an impact on the population include hunting and predation by introduced feral cats, while its restricted distribution makes it vulnerable to the effects of chance natural events, such as disease and drought (3) (6). The introduced population on the Cocos-Keeling Islands is believed to have gone extinct around 1900, due to hunting and a lack of food sources (4).
With the introduction of a hunting ban in 1970, the Christmas imperial-pigeon finally received full legal protection after decades of hunting pressure (2). Today, Environment Australia are currently undertaking several conservation measures aiming to preserve the Christmas imperial-pigeon population. This includes, the establishment of a control programme for A. gracilipes, and the monitoring of the ant’s impact on the ecosystem. It has also been proposed that a captive breeding programme on mainland Australia should be established to facilitate future reintroductions of the Christmas imperial-pigeon (7). Furthermore, a large proportion of Christmas imperial-pigeon habitat is protected by the Christmas Island National Park which was established in 1980, and covers around 63 percent of the island (2) (4).
For more information on the Christmas imperial-pigeon, see:
Birdlife International’s Data Zone:
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- Coverts: small feathers concealing the bases of larger flight feathers, usually on the wings or tail.
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Evergreen forest: forest consisting mainly of evergreen trees, which retain leaves all year round. This is in contrast to deciduous trees, which completely lose their leaves for part of the year.
- Frugivorous: fruit eating/ fruit eater.
- Gizzard: in birds, a thick-walled muscular chamber in which tough food is ground up, sometimes with the aid of ingested pebbles or grit.
- Monogamous: having only one mate during a breeding season, or throughout the breeding life of a pair.
IUCN Red List (August, 2012)
- del Hoyo, J., Elliott, A. and Sargatal, J. (1994) Handbook of the Birds of the World. Volume 4: Sandgrouse to Cuckoos. Lynx Edicions, Barcelona.
BirdLife International (August, 2012)
- BirdLife International. (2000) Threatened Birds of the World. Lynx Edicions and BirdLife International, Barcelona and Cambridge.
- Perrins, C. (2009) The Encyclopedia of Birds. Oxford University Press, Oxford.
- Tidemann, C.R., Yorkston, H.D. and Russack, A.J. (1994) The diets of cats, Felis catus, on Christmas Island, Indian Ocean. Wildlife Research, 21: 279 – 285.
- Garnett, S.T. (2000) The Action Plan for Australian Birds 2000. Environment Australia, Australia.