Thursday, 23 February 2017

The Yellow-crested or Lesser Sulphur-crested Cockatoo. Part 3. History of the Feral Population in Hong Kong

This is the third of a series of articles on this once common but now critically-endangered species from the islands of Indonesia and of Timor Leste.

The feral population of Yellow-crested Cockatoos in Hong Kong has recently hit the headlines. The population is healthier than any of those in their native islands of Indonesia and East Timor. A paper by Like Gibson of the University of Hong Kong and Ding Li Yong of the Australian National University* suggested that such feral populations could be used to repopulate habitats from which they have been extirpated or severely depleted. Science and the Hong Kong newspapers followed up the story. The latter though repeated the canard that the original founders of the introduced population may have been released in 1941 from an aviary at Government House or Flagstaff House just before the surrender to the Japanese.

Anybody with any knowledge of bird watching in Hong Kong in the early 1960s would be aware that the story is a load of old codswallop. Unfortunately, it is perpetuated by the standard book on Hong Kong birds, Birds of Hong Kong, by Clive Viney and Karen Phillipps. Thus my fourth edition (February 1988):

Detailed records have been kept since 1961 but the first introduction if this species is not known for certain. However, one story is that the original birds were released from Flagstaff House (where they were kept in an aviary) in 1941 just prior to the Japanese Occupation.

Virtually the same wording is in the 8th edition of 2005 (retitled The Birds of Hong Kong and South China).

It is not true to say that detailed records have been kept since 1961. The Hong Kong Bird Watching Society was formed in 1957 with a few but very enthusiastic and in some cases very experienced members, including a number with ready access to places like Victoria Barracks in which cockatoos were later seen. Sightings of unusual birds were reported and indeed the first sighting of an individual bird which had escaped was made in 1959.

A photograph I found in Amateur Photographer indicates that Yellow-crested Cockatoos were being imported and kept in Hong Kong in the 1950s:

Photograph by Kwok-Kwan Tam (Hong Kong)
Amateur Photographer 4 May 1955

It seems clear that the accidental introduction of Yellow-crested Cockatoos in sufficient numbers to form viable breeding flocks occurred during the 1960s when large numbers were being imported and kept in Hong Kong (see previous post on exports from Indonesia). It is not surprising that a number escaped, or kept as ‘homing’ birds, or simply released into the wild. Parrot stands, as opposed to secure cages, were popular and it is not difficult to imagine birds managing to escape from the short, light chains and rings that held them close to the perch. An example of one escaping—from a cage in this case—is on Gwulo here.

The story starts in the Hong Kong Bird Report for 1961. John (‘Jack’) Launcelot Cranmer-Byng reported under the heading ‘Escaped Birds’ and the sub-heading ‘Sulphur-crested Cockatoo’:

     There are at present several birds which have recently escaped from captivity. The most striking are the Sulphur-crested cockatoos. Early in 1959 one escaped from a private aviary and established itself in the Shouson Hill area, though it visited the University grounds several times in August and September of that year. It has been seen at intervals at Shouson Hill ever since, and it clearly thrives there. It has been observed on about twenty occasions and has been seen tearing the seeds out of fir cones as well as eating the shoots of a small bush while perched on the ground…While in flight the Cockatoo generally utters loud harsh cries. Its wing beats are laboured and hurried.
      In November 1961 two white Cockatoos were seen together in the Colonial Cemetery at Happy Valley. In January 1962 two Cockatoos were seen together in the University grounds on several occasions when they were observed cracking seeds in various trees. One was a large bird with a fine lemon-coloured crest, and a short length of chain dangling from one leg. This, however, did not appear to impede it in flight or when climbing about in the branches of trees. Its method of feeding was peculiar. It walked along branches very agilely and when it came to some seeds it would bend the twig over with its strong curved beak, hold it firmly with a claw and then proceed to crack the seeds one by one in its beak. The second Cockatoo was much smaller and although it had a small crest it did not appear to be lemon-coloured. 
     Since the bird at Shouson Hill (nicknamed Alexander for reference) does not sport a length of chain from his leg these two birds seen in the University grounds in January 1962 must be two further escapees. From records kept so far it would appear that an escaped cockatoo is quite capable of feeding itself on seeds and shoots and probably fruit, according to the season, while at large in the Colony. It would also seem that when the food supply is insufficient in one area it will fly to another part of the island where it will remain temporarily. No Cockatoos have been seen in the University area since the end of January 1962 though at the time of writing (end of April 1962) a pair have been reported regularly near the Central Government Offices and in the Colonial Cemetery. 
Any evidence of mating among escaped Cockatoos would be of considerable interest, as would any further information on their food supply and which other parts of the Colony they visit. Have they been observed in Kowloon or the New Territories? Have three Cockatoos been seen together at any time?

Jack Cranmer-Byng MC, MA (1919-1999) was Senior Lecturer in History at the University of Hong Kong and one of the two compilers of the 1961 Report. His Military Cross was awarded for gallantry at Arnhem in Operation Market Garden. His unit in the 250 (Airborne) Light Composite Company Royal Army Service Corps had the job not only of organising the supplies but also of defending the perimeter when necessary. The latter role at Arnhem was necessary. The history reads:

     …on the 20th September [1944], Captain Cranmer-Byng was ordered to take an RASC party under cover of darkness and to take over a sector of the perimeter at a point where there was danger of infiltration in the houses flanking the 4th Parachute Brigade position. This movement was successfully accomplished and the line was held, and at one time advanced, for four days in spite of heavy fighting and frequent attacks by mortar, self-propelled guns and single tanks.     Captain Cranmer-Byng was in command of the party throughout and was in much of heaviest fighting. On one occasion, despite a slight wound in the hand, he shot an enemy sniper dead. On another occasion he took a party of men out with a PIAT [Projector, Infantry, Anti Tank in army stores speak] and managed to drive off a self-propelled gun which was attacking the position at short range.     Subsequently, Captain Cranmer-Byng successfully disengaged his party, and led them down in the darkness through the enemy lines to cross the river to safety.     It was largely due to the inspiring leadership and coolness displayed by Captain Cranmer-Byng that the RASC sector held out against very considerable pressure, without food or sleep, and that the party was subsequently able to withdraw to safety when ordered to do so.

Cranmer-Byng was a stalwart of the Hong Kong Bird Watching Society and of the newly formed Hong Kong Branch of the Royal Asiatic Society. He left Hong Kong in 1964 to join the University of Toronto where he continued his interest in birds and the natural world into the 1990s. He died on 6 April 1999 in Canada.

In the 1960s, the University Compound and the hillside above was relatively undeveloped and was an important area for resident birds as well as a hotspot for migrants passing though Hong Kong. Cranmer-Byng reported on what he saw there (he lived in the same block of university flats as we did but we did not overlap).

Back to the cockatoos. From these early descriptions, it is not possible to determine if they were C.sulphurea or C. galerita. The smaller one noted in his report may have been Goffin’s Cockatoo (now called the Tanimbar Corella, Cacatua goffininiana). In the 1964 Report they were listed as C.galerita, again under ‘Escapes’:

This bird features in the 1961, 1962 and 1963 Reports as an escape. Records for 1964 indicate that two or three birds frequented Victoria Barracks from April to July, that two were in the neighbourhood of Sookunpoo in July, August and September, increasing to four seen regularly in that district to the end of the year. One was in the University area in early July. One appeared in May Road in October. One was seen at Ping Shan (the first NT’s [New Territories] record) on April 19 (Society Outing).

In an article in the same issue on birds seen on Broadwood Road, C. Dale reported that 3 or 4 cockatoos occasionally passed through with their raucous aggressive screeching.

The 1965 Report was similar in tone:

Two birds were seen together in 1961 and 1962, three in 1963 and now five in 1965, but there is still no evidence of breeding. The situation is now confused by a report that several of these birds are kept as pets and allowed to fly freely by day.

In the 1966 Report, an article on Birds of Government House Garden by Commander E.D. Webb R.N. (who lived in a flat in Government House) states:

…a flock of five Sulphur-crested Cockatoos, released for a fly-round each morning by a lady who lives near the Church Guest House [1 Upper Albert Road and just over the wall from Government House Garden; Han Suyin was once a resident].

By 1967, there were ‘at least six in the area of Victoria Barracks’ and there is a photograph of two of them taken by Major Rose.

We saw small groups of C. sulphurea flying in the Botanic Gardens/Victoria Barracks area (now Hong Kong Park) from late 1966 until we left in May 1968.

Botanic Gardens, Hong Kong ca 1966
Cokatoos were seen flying over and sometimes landingin the taller trees

By the early 1970s  the feral birds were being shown in reports as Lesser i.e. Yellow-crested Cockatoos (C. sulphurea) as opposed to the larger Australian C. galerita. Reported numbers increased: up to 8 in 1970-71, 13 seen together in 1972 (some Citron-crested) while 21 flew over the Ocean Terminal one evening; total population estimated at 30.

There is a curious statement in the 1973 Report to the effect that lemon crested were outnumbering the sulphur crested. Did the author mean citron-crested (C. s. citrinocristata)? 

By the 1970s it was strongly suspected that cockatoos were breeding in Hong Kong since the birds were seen in the vicinity of a suitable nesting hole. Finally in 1976 breeding was confirmed. On 27 March at Victoria Barracks (now Hong Kong Park), cockatoos were found nesting in a hole in a bombax tree 25 feet off the ground.

Since then the population has increased markedly and by the time we were back in Hong Kong in 1997, groups of cockatoos could be seen more or less anywhere in the north of Hong Kong island from Pokfulam in the west to Happy Valley in the west.

Regardless of whether anything comes of the suggestion of using the successful feral population to restock Indonesian islands, Hong Kong does present an opportunity to investigate experimentally the ecological factors that determine the size, structure and distribution of the population, studies that could not be done on the fragile populations in Indonesia and East Timor but which could provide useful, perhaps vital, information on the conservation and protection of native populations and their habitat.

My guess on the initial preference of escaped/released/homing cockatoos for Victoria Barracks, the Botanic Garden and the University Compound is that there were mature trees in those sites. Hong Kong in the 1960s was very different in terms of vegetation. The hills had been denuded of trees for use as firewood during the Japanese Occupation and it took decades for recovery to occur. A walk up Hatton Road to the Peak or along Conduit Path is an entirely different experience to that in, say, 1966.

Can we deduce from the appearance of the feral birds of the Hong Kong population anything about which part of Indonesia they came? That will be the subject of the next article in the series.

*Gibson L, Yong DL. 2016. Saving two birds with one stone: solving the quandary of introduced, threatened species. Frontiers in Ecology and the Environment. DOI: 10.1002/fee.1449

Additional material added 29 March 2017