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Waterfall Swift Hydrochous gigas

Justification
This poorly known species has a disjunct and probably small population, which is thought to be in decline owing to the loss and degradation of forests within its range. It is currently considered Near Threatened, although more detailed surveys are urgently needed to clarify its status.

Taxonomic source(s)
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.

Synonym(s)
Hydrochrous gigas BirdLife International (2004), Hydrochrous gigas Collar et al. (1994), Hydrochrous gigas gigas BirdLife International (2004), Hydrochrous gigas gigas Collar et al. (1994)

Distribution and population
Hydrochous gigas occurs highly sporadically in the Main Range, Peninsular Malaysia, and the mountains of Sumatra and West Java, Indonesia (Collar et al. 2000). Records from Borneo, in Sarawak and Sabah, Malaysia, and Brunei, involve no specimen evidence and are thus treated provisionally here. All individual populations appear to be small, although one, at Gede-Pangrango, Java, was once fairly large but has seemingly now vanished.

Population justification
The global population size has not been quantified, but the species is described as rare and local (del Hoyo et al. 1999).

Trend justification
This species is extremely poorly known, but several colonies have apparently declined or disappeared in recent years, suggesting that population size may be falling. This is likely to be related to forest loss in areas surrounding breeding colonies. A slow decline is suspected overall.

Ecology
This species occurs over steeply mountainous rainforest, being largely dependent on waterfalls as breeding sites. Altitudinal limits are poorly known, but there are records from 800 m in Peninsular Malaysia, 440 m on Sumatra and 300-1500 m on Java (del Hoyo et al. 1999). Although this species lacks echolocation, it has acute poor-light vision and may be a crepuscular feeder, potentially contributing to the paucity of records.

Threats
This species may be dependent on areas of forest cover surrounding breeding sites, and therefore be susceptible to the effects of logging and landscape conversion for agriculture. The restricted nature of their waterfall breeding sites may pose an inherent limitation to population size, increasing their susceptibility to disturbance.

Conservation Actions Underway
No targeted conservation actions are known for this species.

Conservation Actions Proposed
Conduct surveys throughout the known range in order to determine current status and population size. In particular, clarify its presence, abundance and distribution on Borneo. Conduct ecological studies to explore habitat requirements, particularly the link to rainforest cover surrounding breeding sites. Protect areas of suitable habitat from clearance, degradation and disturbance.

References
del Hoyo, J.; Elliott, A.; Sargatal, J. 1999. Handbook of the Birds of the World, vol. 5: Barn-owls to Hummingbirds. Lynx Edicions, Barcelona, Spain.

Further web sources of information
Detailed species accounts from the Threatened birds of Asia: the BirdLife International Red Data Book (BirdLife International 2001).

Text account compilers
Benstead, P., Gilroy, J., Taylor, J.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2014) Species factsheet: Hydrochous gigas. Downloaded from http://www.birdlife.org on 13/07/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 13/07/2014.

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 Near Threatened
Family Apodidae (Swifts)
Species name author (Hartert & Butler, 1901)
Population size Unknown mature individuals
Population trend Decreasing
Distribution size (breeding/resident) 108,000 km2
Country endemic? No
Links to further information
- Additional Information on this species