A Report on the White-Winged Wood Duck in Southern Sumatra
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A report on the White-winged Wood Duck in southern Sumatra D. A. HOLMES The presence of the White-winged Wood primary plains forest (Mackenzie & Kear Duck Cairina scutulata in J ambi province of 1976), in Sumatra they appear to tolerate Central Sumatra, and in Sumatra’s southern very much more open and disturbed forest. most province of Lampung, has previously My own records come mostly from remnant been reported (Holmes 1976). From April patches of woodland in the swamp, or dense 1976 to January 1977 some time was old secondary dryland forest adjacent to the devoted to searching for this bird particular swamp. Sometimes the ducks use quite open ly during the last month. A brief report is woodland with little shade, though probably presented on the findings. suitable tall trees must always be present. At night they feed out in the grasses of the open swamp. In Jambi they were seen in the Habitat weedy stubble of swamp rice and they may The province of Lampung (formerly part of feed in plots of young rice, but presumably the province of South Sumatra) lies between they would not visit the intensive irrigated latitudes 4° and 6° South, and has an ricefields on adjacent dry land. equatorial climate of constant high Many of these habitats are close to quite temperature. There is a wet season between large villages, and indeed the ducks ap November and March and a drier season parently breed within shouting distance of between May and September. In a few years such villages. They are relatively undisturbed there are droughts of up to three months, on their night feeding grounds, but it is im which allow some of the swamps to dry out. portant to know how much interference they The province has extensive low plains, will tolerate in their daytime roost or with ranges of mountains along the western breeding place. In the Jambi locality, the side, and swamps near to the east coast (see ducks were feeding in daylight within 70 Figure 1). Rain forest formerly covered the metres of three occupied farmer’s huts, but whole province, but primary forest is now of course they would fly off at human confined to the most remote mountainous approach. areas. Patches of primary forest and more extensive secondary forest remain in the north and east of the plains, but shifting Diurnal rhythm cultivation has left very extensive grasslands As in Assam, the birds flight just before and scrub. dusk, at around 18.15 local time, when it is Freshwater swamps extend along the main almost too dark to see them. They return just river valleys and broaden out near the coast, before dawn, at about 05.30, or if un where they become somewhat peaty. In an disturbed they may remain on the open area of 24,000 sq km of plains, there are swamp until the middle of the morning. I some 1,400 sq km of open swamp and 730 have flushed a bird at midday, and another sq km of swamp forest (Howard Humphreys in the late afternoon (17.00). They almost in et al. 1977). These figures are based on air variably call in flight and thus readily reveal photographs taken in 1969. They refer to all their presence. They may fly four kilometres the plains area except the Mesuji river basin or more across open and populated terrain in the north. A dominant tree in the swamps between their roost and feeding grounds. All is a form of rengas (probably Melanorrhoea my sightings have been of either one or two sp.), a tall and imposing tree that has an birds. abundance of natural cavities. The open swamps have secondary vegetation of grass and tall scrub, with groves of trees in places. Description The White-winged Wood Duck is a Except for the bird reported previously in familiar bird to many villagers under its In Jambi, I have seen them only in flight and donesian name of ‘Bebek hutan’, meaning have never obtained a full description. I have forest duck, or its Lampungese name of now seen a total of five birds in Sumatra ‘Serati’. In contrast to Assam and elsewhere, (others being only heard), and every one where the ducks require the shelter of heavy showed a considerable degree of albinism so Wildfowl 28 (1977): 61-64 61 62 D. A. Holmes that the impression has been that of a Figure 1), I was shown four reputed nest predominantly white bird with irregular holes, all in rengas trees standing in swamp. black markings. In discussion with Mr Three of these were sites of previous years. Mackenzie and Dr Kear, it was pointed out One was four metres up in a deep hollow in that inbreeding, which is thought to be a the fork of a tree standing in a dense grove of cause of albinism, may be associated with woodland. Villagers reported that this site the greater tolerance to habitat variety and had been visited again in January 1977, but to human disturbance shown by Sumatran there was no sign of breeding. Another birds. Another factor encouraging inbreeding former site, also still visited sometimes, was a may be the perennial nature of many of the hole eight metres up in the straight trunk of a swamps, which only dry up in very dry tree standing in the open in deep swamp. The seasons, thus allowing the birds to be more site used in January 1977 was five metres up, sedentary than they would be in a more in a large hole in the decaying trunk of an old monsoonal climate. tree, standing in the tall grass of an open swamp in which the remaining trees had been burnt in a previous year. This site Breeding would be exposed to sunlight and it is in Around the village of Bujung Tenuk, near teresting that it was chosen when a dense Menggala in North Lampung (site A on and apparently more suitable grove of trees Figure 1. Location of White-winged Wood Duck in Lampung Province, South Sumatra White-winged Wood D u c k 63 was available a hundred metres away. Mackenzie & Kear (1976), suggest that On 15th January the nest contained 8 one pair per 100 ha of ideal environment is eggs, one of which was said to have been laid probably maximal population density in within the last two days. All the eggs were N.E. Assam. In the Menggala area of Lam wet and extremely stained and it was im pung there could have been four pairs pre possible to determine which was the newest sent in an area of 500 ha, though some of the egg. They weighed between 80 and 87 grams villager’s information may have been and measured 66-69 x 48—50 mm. duplicated. In more densely populated areas It is important to stress that I did not ac of the province, or in the more extensive tually see a bird at this nest though I heard coastal swamps, one pair per 500 ha might one near it at night. It is possible that the be a more reasonable estimate, though it is nest had been abandoned a month or so not possible to guess what the total popula previously. There is even a remote chance tion is. that the villagers had deceived me, for finan cial gain, by placing eggs of domestic Factors in conservation Muscovy Duck Cairina moschata in the hole! The White-winged Wood Duck has been ful The ducks are said to breed in the wet ly protected in Indonesia since a decree of season. In mid-January, when the eggs were 1972, although at present the effect of such examined, villagers reported having seen an protection is limited, since there is no adult with two ducklings in the swamp at evidence of direct hunting pressure on this or night, while a family of seven ducklings was any other duck in Sumatra. There are no said to have been captured the previous guns among the general rural population, week. I was unable to confirm these reports. and apart from those birds that are popular The guide to one of the sites said that the as cage birds, hunting is largely restricted to birds would not breed until the level of the big game hunters and local trappers. flooded swamp had risen another metre. Villagers would take casually any duck eggs Probably the species has a fairly extended for food, but these would be mostly the In breeding season lasting from December to dian Whistling Duck D endrocygna javan ica March or April. which is very common. Ducklings are sometimes netted at night using strong lamps. Population Loss of habitat and human overpopula I was able to confirm that birds were present tion are therefore the main threats to the at every piece of suitable habitat which I sur duck in Sumatra. Although tolerant of con veyed, namely the Menggala area on the siderably more disturbance than elsewhere in Tulang Bawang river (A on Figure 1), Rawa its range, it is assumed that birds present in Susuk on the Seputih river north of Rumbia seriously disturbed sites are a remnant pop (B), in the Way K ambas reserve (C) and at ulation, and that numbers have already two sites near Jepara (D), and along the declined considerably in the more densely Ketibung tributary of the lower Sekampung settled lands. Incoming farmers will continue river (E). This was seven sites in all, and to clear all the remaining dryland forests and villagers clearly knew the bird at other sites.