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Polynesian Imperial-pigeon Ducula aurorae
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Justification
This species qualifies as Endangered because it has a very small population, and almost certainly only now occurs on only one very small island. Although it may currently be increasing there owing to a cessation of mining activities and hunting, it has a very small population and could decline rapidly in the near future owing to habitat destruction, or if Swamp Harrier Circus approximans colonises the island. Confirmation that the population is larger than previously thought, and further clarification of future potential threats, may show that the species warrants downlisting to a lower category of threat.

Taxonomic source(s)
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.

Identification
51 cm. Large, knob-billed pigeon with broad rounded wings. Silver-grey head and most of underparts, dark bronzy-green upperparts, black undertail-coverts. Similar spp. Feral pigeon Columba livia much smaller and does not live in forests. Voice Gruff, hoarse rouw-rouw-rouw and variety of quieter notes.

Distribution and population
Ducula aurorae is known from Tahiti in the Society Islands and Makatea in the Tuamotu Archipelago, French Polynesia. On Tahiti, it may already be extinct, it was restricted to the Papeno`o and Hitia`a valleys in 1986-1990 (Monnet et al. 1993b), but none were reported in 1998 and in 2006 it was considered unlikely to persist (Thibault and Cibois 2006). On Makatea, the population was judged to lie between 100 and 500 individuals in 1986-1987, but have since increased following a reduction in hunting (Thibault and Guyot 1987, Thibault and Cibois 2006). A survey on Makatea in 2009 estimated the total population size at 1,206 individuals (95% C. I., 867-1,677) (Albar et al. 2009, 2010). Further clarification of this estimate is needed. It is unclear whether this represents a genuine population increase, however the cessation of mining activities and reduction of the human population inhabiting the island represent prospects for population recovery of many of the native birds on Makatea. There are also fossil records indicating that it was once more widespread, including in the Southern Cook Islands (Steadman 1989).


Population justification
A survey on Makatea in 2009 (Albar et al. 2009, 2010) estimated the total population size at 1,206 individuals (with a 95% confidence interval of 867-1,677 individuals, roughly equating to 570-1,200 mature individuals). Further clarification of this estimate is needed, and the previous estimate of 100-500 mature individuals is precautionarily retained until higher numbers can be confirmed.

Trend justification
Population estimates are too inaccurate to detect trends, although hunting has been much reduced and the species may be increasing on Makatea where forest is regenerating. An overall increase of 1-9% is suspected to have taken place over the last ten years. However, a future decline is very possible given the plans for infrastructure development and the distinct possibility that C. approximans could colonise the island.

Ecology
Though the species was formerly found only in dense forest, where it feeds on fruit from a variety of native and introduced trees, it has recently spread into secondary habitats and even gardens (Holyoak and Thibault 1984, Pratt et al. 1987, Thibault and Guyot 1987, Te Manu 1998, Thibault and Cibois 2006). It is now an important seed disperser on Makatea, accelerating the spread of native forest into areas which had been mined (Thibault and Cibois 2006).

Threats
On Makatea, much of its habitat was destroyed during the period 1917-1964 as a result of phosphate mining, however it is now spreading as vegetation recovers and hunting is reduced (Thibault and Guyot 1987, P. Raust in litt. 1999, Thibault and Cibois 2006, Albar et al. 2009, 2010). However, Makatea is being considered for new mining activities, which may further affect the birds (Albar et al. 2010). The proposed mining project is now dormant but may be resurrected in future (P. Raust and C. Blanvillain in litt. 2013). A proposed runway and associated road and infrastructure development is likely to lead to renewed deforestation (Thibault and Cibois 2006). Predation by introduced cats and rats (particularly black rat Rattus rattus) may be a problem (Monnet et al. 1993b), although the species has coexisted with rats for several decades (J.-C. Thibault in litt. 2000). On Moorea, Tahiti and other formerly inhabited islands, its extinction may have been the consequence of the spread through the Society Islands of the Swamp Harrier Circus approximans (Holyoak and Thibault 1984, Thibault 1988, Seitre and Seitre 1991, Thibault and Cibois 2006). This species continues to spread throughout the region, and its arrival on Makatea would be disastrous for D. aurorae (Thibault and Cibois 2006).


Conservation Actions Underway
On Tahiti, a year-long study in 1998 collected information from the inhabitants of the valleys where it was last recorded (J.-C. Thibault in litt. 2000). Work was carried out in 2009 by Société d’Ornithologie de Polynésie Manu to determine the population size of the species through distance sampling (Albar et al. 2009, 2010). Conservation Actions Proposed
On Makatea, resurvey the population (P. Raust in litt. 1999) in order to assess both numbers and distribution within primary and regenerating forest.

On Tahiti, conduct field surveys to confirm its extirpation. Ensure C. approximans does not become established on Makeata by developing a reporting system for residents. Eradicate C. approximans from Tahiti and the Society Islands to prevent it spreading to Makatea. Oppose plans for a large runway on Makatea, support instead plans for a smaller runway. Continue to oppose plans for phosphate mining on Makatea. Consider captive breeding and reintroduction to Tahiti.

References
Albar, G.; Dylan C. Kesler, D. C.; Gouni, A. 2010. Observations and status of birds of Makatea and Niau Islands, Tuamotu Archipelago, French Polynesia..

Albar, G.; Gouni, A.; Kesler, D.; Autai, T.; Serra, C.; Faulquier, L. 2009. Etude de l'avifaune endémique de l'île de Makatea (archipel des Tuamotu, Polynésie française).

Holyoak, D. T.; Thibault, J. -C. 1984. Contribution à l'étude des oiseaux de Polynésie orientale. Memoires du Museum National d'Histoire Naturelle - Serie A: Zoologie 127: 1-209.

Monnet, C.; Thibault, J.; Varney, A. 1993. Stability and changes during the twentieth century in the breeding landbirds of Tahiti (Polynesia). Bird Conservation International 3: 261-280.

Pratt, H. D.; Bruner, P. L.; Berrett, D. G. 1987. A field guide to the birds of Hawaii and the tropical Pacific. Princeton University Press, Princeton.

Seitre, R.; Seitre, J. 1991. Causes de disparition des oiseaux terrestres de Polynésie Française. South Pacific Regional Environment Programme, Nouméa.

Steadman, D. W. 1989. Extinctions of birds in Eastern Polynesia: a review of the records and comparisons with other Pacific Island Groups. Journal of Archaeological Science 16: 177-205.

Thibault, J. -C. 1988. Menaces et conservation des oiseaux de Polynésie Française. In: Thibault, J.-C.; Guyot, I. (ed.), Livre rouge des oiseaux menacés des régions françaises d'outre-mer, pp. 87-124. Conseil International pour la Protection des Oiseaux, Saint-Cloud.

Thibault, J. -C.; Guyot, I. 1987. Recent changes in the avifauna of Makatea Island (Tuamotus, Central Pacific). Atoll Research Bulletin 300: 1-13.

Thibault, J.-C.; Cibois, A. 2006. Une situation favorable pour le Rupe de Makatea. Te Manu 54: 2-3.

Further web sources of information
Alliance for Zero Extinction (AZE) species/site profile. This species has been identified as an AZE trigger due to its IUCN Red List status and limited range.

Click here for more information about the Alliance for Zero Extinction (AZE)

Explore HBW Alive for further information on this species

Search for photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Derhé, M., Mahood, S., O'Brien, A., Shutes, S., Stattersfield, A. & Symes, A.

Contributors
Raust, P., Thibault, J., Kesler, D. & Blanvillain, C.

Recommended citation
BirdLife International (2014) Species factsheet: Ducula aurorae. Downloaded from http://www.birdlife.org on 18/09/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 18/09/2014.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Key facts
Current IUCN Red List category Endangered
Family Columbidae (Pigeons, Doves)
Species name author (Peale, 1848)
Population size 100-500 mature individuals
Population trend Increasing
Distribution size (breeding/resident) 25 km2
Country endemic? Yes
Links to further information
- Additional Information on this species