A male Musk lobata swimming (top) and in display (middle) (Klaus Kussmari). (Bottom) The Slimbridge female visiting one of her males (Mary Evans). 113 The

The photographs on the opposite page are of pouch inflated. Whilst holding this attitude the M u s k D u c k Biziura lobata, an inhabitant the feet are kicked outwards and backwards, of southern and . It is a before being returned to the accompaniment member of the tribe of Stifftails, the , of a loud ‘plonk’ as they hit the water. As a group of nine which are not closely m any as 50 Plonk-kicks m ay be performed in related to any other . Their main rapid succession. The climactic display is the characteristics include the long stiff tail Whistle-kick in which the tail is fanned and which give them their name, a broad held right over the back instead ofjust upright bill, high at the base, short stubby wings, and as in the Plonk-kick. The feet again kick out­ rather large feet. The neck, unlike that of wards and backwards and simultaneously the other ducks, is short and thick, and can be in­ emits a sharp clear whistle. The flated in display. photograph shows the posture adopted The sexes of the Musk Duck are alike in between successive kicks of the feet in a series , though the female is considerable of Whistle-kicks. smaller, only one-half to one-third the weight. Johnsgard (1966), who has published by Both sexes have a throat, or guiar, pouch but far the best description of the Musk Duck dis­ only the male’s is inflatable, and is additional play, has suggested that the audible signals to the inflatable air-sac in the throat. The during the display may be of value to the bird name comes from the strong musk odour that in the overgrown swamps where it breeds. the male can emit from its preen gland. The The inflated throat feathers and pouch are purpose of the odour is unknown. thought to be important in sexual selection Musk Ducks breed on deep fresh water, rather than as a species isolating mechanism, preferably with thick emergent vegetation there being no congeners of the Musk Duck in round the margins. In winter they resort to a Australia, and chances of hybridization with wider variety of wetlands including rivers and the much smaller Blue-billed Duck Oxyura estuaries. Their nest is a well concealed cup of australis, the other Australian stifftail, seem reed stems and leaves, usually in the centre of remote. a thick clump. A small amount of down is We have two males and one female Musk plucked to line the nest. The clutch size is Duck in the collection at Slimbridge, the only small, only 2 -3 (mean 2 -8), though up to ones outside Australia. We have already had 10 eggs have been found in one nest, evidence of the extreme aggressiveness of the presumably the product of at least two male, reported by Delacour (1959), when the females. The incubation period is not known. male of our original pair cornered the female Frith (1967), from whom these breeding in the aviary where they were kept and nearly details are taken, reports that unique among killed her. After that incident the were ducks the young are fed by the female. kept in separate though adjacent pens. The upper photograph shows the low-in- However as successful breeding could only be the-water, short-necked profile of the swim­ achieved by keeping them together some ming bird, with the stiff tail feathers flat on the mechanism had to be devised of preventing water where they are clearly acting as a the male from carrying out further attacks on rudder. The pouch is uninflated and hangs the female. The Curator’s ingenious solution down loosely. In the lower picture the male is to this problem was to place a board in the tail-cocking with the pouch fully inflated. The channel of water that separates the two pens courtship of the female by the male is per­ and to cut a number of holes in the board just formed by three main behavioural postures, at water level. Their diameter allows the ready the Paddling-kick, the Plonk-kick, and the passage of the female, but the much larger Whistle-kick. In the first the bird lowers itself male cannot get through. Thus when the along the water and then kicks sharply back female wants to join the male she can, but if he with both feet, splashing water a metre or two becomes too aggressive, she can escape from into the air. A few kicks like this lead into the him. Currently there is one male in each of the Plonk-kick where the head is held upwards pens and the female is free to move from one with the neck and cheeks puffed out and the to the other as the whim or the need arises. References Delacour, J. 1959. The Waterfowl o f the World. Vol. 3. London: Country Life. Frith, H. J. 1967. Waterfowl in Australia. Sydney: Angus and Robertson. Johnsgard, P. A. 1966. Behavior of the Australian Musk Duck and Blue-billed Duck. Auk 83: 98-110. M.A.O.