|Wing-clipped cockatoo at Guangzhou Zoo|
( Gmelin, 1788)
|Native (blue) and introduced (red) ranges of C. sulphurea|
The yellow-crested cockatoo (Cacatua sulphurea) also known as the lesser sulphur-crested cockatoo, is a medium-sized (about 34-cm-long) cockatoo with white plumage, bluish-white bare orbital skin, grey feet, a black bill, and a retractile yellow or orange crest. The sexes are similar.
The yellow-crested cockatoo is found in wooded and cultivated areas of East Timor and Indonesia's islands of Sulawesi and the Lesser Sundas. It is easily confused with the larger   and more common sulphur-crested cockatoo, which has a more easterly distribution and can be distinguished by the lack of pale yellow coloring on its cheeks (although some sulphur-cresteds develop yellowish patches). Also, the yellow-crested cockatoo's crest is a brighter color, closer to orange.  The citron-crested cockatoo, which is a subspecies of the yellow-crested cockatoo, is similar, but its crest is clearly orange. 
Traditionally, four subspecies have been recognized:
- C. s. abbotti (Abbott's lesser sulphur-crested cockatoo) – Masalembu Islands
- C. s. citrinocristata ( citron-crested cockatoo) – Sumba
- C. s. parvula (Timor sulphur-crested cockatoo) – Sumbawa, Komodo, Flores, Timor, and various other islands in the Lesser Sundas
- C. s. sulphurea ( nominate subspecies) – Sulawesi and nearby smaller islands
Based on recent evidence, three additional subspecies should be recognized (bringing the total to seven): 
- C. s. djampeana – Tanah Jampea
- C. s. occidentalis – Lesser Sundas from Lombok to Alor (thereby restricting C. p. parvula to Timor)
- C. s. paulandrewi – Tukangbesi Islands
The yellow-crested cockatoo nests in tree cavities. The eggs are white and usually two in a clutch. The incubation is shared by both parents. The eggs are incubated for about 28 days and the chicks leave the nest about 75 days after hatching. 
The yellow-crested cockatoo is critically endangered.  Numbers have declined dramatically due to illegal trapping for the cage-bird trade. Between 1980 and 1992, over 100,000 of these birds were legally exported from Indonesia, yet a German proposal submitted to CITES to move it to Appendix I  was not approved. It has since been moved to Appendix I.  The current population is estimated at fewer than 2,500 individuals and is thought to be declining in number. 
The subspecies C. s. abbotti is found only on the island of Masakambing. Its population on this tiny island (about 5 km2 or 1.9 mi2) had fallen to 10 as of June and July 2008. The decline results from trapping and logging, especially of mangrove ( Avicennia apiculata) and kapok trees. 
Several national parks provide protection of their habitat, including Rawa Aopa Watumohai National Park on Sulawesi, Komodo National Park on Komodo Island, the national parks of Manupeu Tanah Daru and Laiwangi Wanggameti on Sumba, and the Nino Konis Santana National Park in East Timor (Timor-Leste). 
An introduced population of these birds is found in Hong Kong.  They are a common sight across the densely populated area on both sides of the harbour, easily spotted in the woods and public parks in the north and west of Hong Kong Island. The large group has apparently developed from a number of caged birds that have been released into the Hong Kong area over many years.  An often repeated story is that Hong Kong Governor Sir Mark Aitchison Young released the Government House's entire bird collection – including a large number of yellow-crested cockatoos – hours before surrendering Hong Kong to Japanese troops in December 1941. 
- BirdLife International (2018). "Cacatua sulphurea". IUCN Red List of Threatened Species. 2018: e.T22684777A131874695. doi: 10.2305/IUCN.UK.2018-2.RLTS.T22684777A131874695.en. Retrieved 13 November 2021.
- BirdLife Species Factsheet, retrieved 10 February 2010
- Birds in backyards factsheets: Sulphur-crested Cockatoo
- Yellow-crested and sulphur-crested cockatoo on Flickr - Photo Sharing!
- Alderton, David (2003). The Ultimate Encyclopedia of Caged and Aviary Birds. London, England: Hermes House. p. 204. ISBN 1-84309-164-X.
- N.J. Collar, N.J.; and Marsden, S.J. (2014). The subspecies of Yellow-crested Cockatoo (Cacatua sulphurea). Forktail 30.
- CITES proposal
- "Project Bird Watch / Indonesian Parrot Project - How You Can Help". October 1, 2008. Retrieved 2008-10-24.
- Wu, Venus. "How an endangered cockatoo took over Hong Kong". Goldthread. South China Morning Post. Retrieved 20 May 2020.
- Zabrina Lo (3 July 2019). "The foreign origins and uncertain future of Hong Kong's cockatoos". Zolima Citymag. Retrieved 15 August 2021.
- HK Magazine Friday, February 18th 2005, pp6-7
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