The Sulphur-crested Cockatoo, Cacutua galerita, was first recorded in Sentosa on 4 November 1987. It has now become a fairly common escapee with an established population on the island. They have been seen across from Sentosa at Mount Faber, as far as Loyang and inland at Bukit Batok. They are often seen in the company of the Tanimbar Corella, C. goffiniana and the Yellow-crested Cockatoo, C. sulphurea.
The many large old trees at Sentosa like this Heritage Angsana (left) and Ficuses, make ideal roosting and nesting holes for these gregarious birds. I went over in May 2015 to check on a family of cockatoos that was seen roosting inside a tree cavity when a main branch broke off most probably during a thunder storm. I wanted to see if they are breeding there. A pair of Oriental Pied Hornbills, Anthracoceros albirostris came by to check if there are any more cavities for them to nest. I suppose they will try to take over the cavity from the Cockatoos if it is suitable.
When I arrived I found one cockatoo perched outside the cavity. It looked and behaved like a young adult. It just stayed around the entrance, moving in and out of the cavity. It did not mind my close presence at all. If it had just fledged, then I must have missed documenting its breeding. So far we do not have any records of this species breeding, but judging from the number of these cockatoos in Sentosa, they must be reproducing here.
After a while a pair of Cockatoos flew in, started screaming and then preening each other. I can only assume that this family group is sharing the same cavity. The younger bird did at one time flew off with the others to a nearby tree but returned shortly and hang around the cavity. They also had a habit of chewing off young branches of the Angsana and let it dropped down to the ground. I have no idea why they do that. I had seen this behavior at Dempsey Hill when an adult chewed on a Pong Pong fruit and letting the pulp and fruit dropped away.
If these cockatoos are confined to Sentosa within a small population, their presence and that of the Peacocks and Hornbills will at the very least give visitors an introduction to nature in Sentosa.
Reference: The Avifauna of Singapore. Lim Kim Seng, 2009.