White-backed Duck Behaviour 71

The behaviour of the White-backed Duck

A. C LARK

Introduction up instantly when a Marsh Harrier Circus These observations on the White-backed ranivorus flies near, or move away from Duck Thalassomis leuconotus were under­ an approaching Coot Fulica cristata. taken to check and extend those which Maccoa, Southern Pochard Netta erythro- Johnsgard (1967) made on captive birds, phthalma and Red-billed Pintail Anas because of the apparent lack o f informa­ erythroryncha have also been seen tion on this species in the wild. They amongst the White-backed Duck. Often were made on ducks which were present when disturbed from their sleep the latter for varying periods at three dams and one push their heads up and will often Wing- natural pan situated in the vicinity of the flap. The sequence, Nibbling - preen, Witwatersrand, Transvaal, South Africa. Shake and Wing-flap is not unusual at The waters were relatively shallow, with this time and Leg-wave, Wing-and-leg- maximum depths varying from two to six stretch and Head-scratch may also be seen. feet. Although sedges and other aquatic The break up of sleeping parties takes plants provided suitable nesting sites, no place gradually. Single birds or small breeding took place during the period of groups will leave and go on their way to observation, i.e. July 1968 to April 1969. feed. Flights just above the water surface The names of the various comfort move­ for distances of ten feet to fifty yards are ments described are taken from M c­ occasionally taken. There are often short Kinney (1965) and for the movements swimming movements with little apparent associated with threat and copulation the purpose. These involve direction changes, names are taken from Johnsgard (1967). movements away as though avoiding, movements towards as though asserting Resting or sleeping and much pausing with head partly raised and held stiffly. The birds rest or sleep on the water in groups, invariably with the beak tucked Feeding into the scapulars, the distances between individual birds varying from one foot to The White-backed Duck feeds by diving two yards. At such times the tail is incon­ to the floor of the water and sifting food spicuous but sometimes it is raised slightly from the mud or debris resting there. off the water. At Spaarwater where the Although Clancey states the birds dive greater portion o f the water surface was with a leaping action and Johnsgard con­ choked with mats of grass stalks and firms this, all the Whiteback under obser­ other aquatic plants, they preferred this vation made a smooth plunge like the area and were never seen very near the Maccoa except that the birds made a shore nor resting in open water. This splash dive when avoiding a Coot. The seems to be the general pattern, but at Fulvous Whistling Duck Dendrocygna Impala Park they had to move very close bicolor lifts part or the whole of its body to the shore to get anchorage of this type clear of the water when diving but may and would sometimes sleep in open water frequently feed by ‘ up-ending.’ The where, like the Maccoa Oxyura maccoa, Whiteback does not move far laterally they would drift in the wind. Although under water when feeding. In water Clancey (1967) states that Whiteback approximately one foot deep I have re­ repair to dry land for rest, I would con­ corded 12-14 seconds under water and sider this exceptional for the study area. 4-6 seconds between dives above. At Frequently a bird may be seen sleeping Spaarwater where the depth was two to with one expanded webbed foot visible, three feet, time under water varied from sometimes with both feet sticking out on 15-20 seconds, time on surface from 5-10 either side like fins, and this habit may seconds. At Tweefontein Dam where the explain their preference for the anchorage water had an estimated depth of six feet, provided by stalks of aquatic plants. I recorded 25-30 seconds under water and During the daytime most birds sleep for 7-12 seconds above. Feeding from the sur­ three to four hours in the late morning face is unusual. The times under water with casual shorter spells at other times. agree closely with those given by Johns­ The greater part o f the day is spent gard but he gives a more extended period sleeping, giving the impression that the on the surface between dives. birds are inactive. Although they are Whilst on the surface between dives I apparently sleeping, they push their heads have seen birds tread water, the feet 72 Wildfowl pushing water downwards, not backwards than exercise, take place at from 5-30 feet as when swimming. This behaviour is and the birds keep over the water. evidenced in the slight rocking movement T w o typical instances of pre-flight be­ of the body and the movement of the haviour were recorded as follows : ‘ Six surrounding water. As a result of the birds swam off in single file. After a short treading action the body is lifted notice- distance they mostly turned to face the ably and the breast prominentiy displayed. wind with heads up. There was a pause The treading continues until the birds and I saw one bird Shake and two Wing- dive again and it is possible that they flap. After another pause I saw one lateral behave in this way when they are feeding Head-shake. There was another brief in rather shallow water, the slight lift of pause and they all flew off and did a the body facilitating the dive. figure-of-eight over the pan.’ ‘ T w o birds As the water level at Spaarwater drop­ with heads up faced the wind. They ped, the birds occasionally fed where the turned and swam with the wind. After a surface water was matted with grass. Here short distance they turned to face the they had to struggle to surface properly wind, hesitated and then swam again with and sometimes the head only came out. the wind. They repeated this movement Before diving again they would lower the a third time before facing the wind to beak on to the breast. Occasionally when take off.’ a bird surfaces it carries a string of weed It is evidently important for the White- in its beak which it makes no attempt to back to have a good stretch of water in swallow. Sometimes the head is blackened front before attempting to fly. I have seen by debris the bird has stirred up in feed­ a bird swim 100 yards with the wind to ing. At Spaarwater Coots frequently fed enable it to get into a position to take off in the wake of a diving bird. into the wind. The Head-shake is not The main observed feeding times are often used and when it is, is not neces­ from dawn to shortly after sunrise and sarily repeated by other birds in the in the late afternoon until sundown. At group. Pre-flight behaviour is mainly Spaarwater they mainly chose the areas recognised by birds gathering, hesitating where the surface water was free of vege­ with their heads up and facing into the tation and the birds joined together in wind. Flight is not always simultaneous. groups of varying sizes. Once feeding Quite frequently after flight I have seen commenced the birds continued steadily birds rest with beak in scapulars. and some fed for 60-80 minutes without a break. Sometimes they would cease for Voice a period and then continue feeding. The main call of the Whiteback consists of a double note which sounds like ‘Tit-weet,’ Flight reed-like, with the second longer note The Whiteback seldom flies during the lower than the first. When on the water day and when it does, like the Maccoa, the bird puts its head right up to call. it has difficulty in getting airborne and Single birds may call between dives, or paddles the surface for 10-20 yards before during a pause in swimming or during a rising clear. For this reason it usually takes break from sleep, but occasionally others off into the wind and prefers windy days. will join in. The call is sometimes given Its wings beat steadily and it appears to during a take-off, during flight or immedi­ have little manoeuvreability. It flies with ately after coming down on water. The legs to the rear protruding beyond the double note is often repeated several tail. Before landing, its legs are lowered times and I have heard one bird repeat and the webs of the feet fanned out, as the call at intervals over a period of 50 if as air brakes, before being moved for­ minutes when it seemed to have no signal ward to take the impact of the water. value. It is also sometimes heard after Even so the bird usually ploughs into the disturbance occasioned by people or an water with its breast. I have not seen them aggressive approach of another bird. The come down on land. ‘ Tit-weet ’ call carries well and can To reach another bird, or to feed, some readily be heard at a distance of 100 take short flights of ten yards just skim­ yards or more. Johnsgard also records a ming the water or longer flights in a ‘ conversational ’ or contact call consisting direct line at a height of approximately of three to five notes uttered on a rising four feet. Protracted flights of a more series of soft whistles. formalised nature, by two or more birds, occur in the afternoon when they rouse Comfort movements themselves prior to feeding. These flights, The Swimming-shake or Shake begins which seem to have no other purpose with the wing feathers being slightly White-backed. Duck Behaviour 73 raised and shuffled, followed by the head the day and at Spaarwater the birds would being lifted and the breast raised off the get on to a Coot’s platform and concen­ water to give a brief shake. In the final trate on cleaning their breast feathers. position the beak is often pointed up­ wards. There is no forward movement. Threat The Swimming-shake may be seen during a break in sleep, following disturbance Threat display seems to take place mostly and during the bathing and preening after pair formation. When swimming one periods which follow feeding. Sometimes member of a pair will drive away another the Tail-wag precedes the shuffling of the bird. The following patterns have been wing feathers but because o f the short observed: (1) One bird would swim to­ tail it is not easy to see. The Tail-wag wards another with its head on its may be performed on its own during shoulders and the other bird would re­ preening or swimming. The lateral Head­ treat sometimes by diving. At times the shake may occur before or after flight but bird approached would not retreat but it can be seen also during preening pushed its head up and slightly back­ periods. wards in the Head-back posture. The The Wing-flap behaviour o f the White- approaching bird would do the same and back differs little from the pattern com­ the two birds would pause for a few mon to dabbling ducks. The body is, seconds side by side often looking in however, often lifted clear o f the water opposite directions. Occasionally they when the treading action of the feet can would remain in this rather statuesque be seen. On these occasions the body is position for more than a minute. (2) One nearly erect and the flapping may be pro­ bird would take a flight of 3-4 yards tracted for ten or more seconds. The towards another, often paddling all the movement may occur during a break in way. The other would dive in retreat or sleep when several birds will perform in push its head up and the two would adopt succession. It also occurs after disturb­ the side by side head-up position. (3) The ance, after flight and during preening. aggressive bird would swim quickly with During sleep on the water the feet are beak open and attempt to grab the other usually hidden under the wings. Occasion­ bird which would retreat quickly. (4) One ally a foot will be brought out and waved bird would swim towards another with before being returned to its resting place; head forward. The other bird would go this Foot-shake is also seen in the Maccoa to meet the threat and as they reached Duck. In the Whiteback, however, the each other they would rear up with head foot may be left exposed. Wing-and-leg- high on extended neck and breast off stretch behaviour may be seen during a water. There would be no contact but break in sleep and also during preening. they would pass over each other’s shoul­ Scratching of the head or neck with the ders and resume their normal swimming foot occurs mainly during preening posture. I have seen the aggressed bird periods. dive after such an encounter. Invariably after an extended feeding period the Whiteback bathes and preens Pair formation often for 10-15 minutes at a time. Bathing The following incident, which I believe begins by the bird dipping its head and to be typical of paired birds, was recorded withdrawing it quickly to throw water in the late afternoon. ‘ T w o birds swam over the back. Shoulder-rubbing is often forward, side by side, with heads partly combined with bathing and performed up and held stiffly. One bird, which I when the head is thrown backwards. think was the drake, seemed bigger than Then follows Wing-thrashing usually with the other and its breast was more prom­ both wings together. On one occasion inent. The smaller bird dived and swam only have I seen a bird do a partial underwater. The other bird swam to join somersault. I have not seen Dashing-and- it as it surfaced. The smaller bird dipped diving. Preening and oiling follows bath­ its beak as if to feed from the surface. ing when much attention is given to the The other did the same and again both breast feathers, tail and underside of the immersed their beaks. Both birds then wings. Shoulder-rubbing is frequently swam off in a dignified way with head seen. During preening the bird may erect and joined other birds to feed.’ On Head-shake, Shake, Wing-flap, Tail-wag, another occasion the birds swam round Scratch head or shake the wings. W ing- in a circle about 5 feet diameter, dipping thrashing may also be seen. Nibbling- their beaks frequently. I have seen no preening may occur at any time during especial male courtship display. 74 Wildfowl

Copulation ing. Then the female was seen to Wing- Copulation was seen at Spaarwater, a flap and Preen. Eventually they swam natural pan, on three occasions in August away side by side with heads erect. These between 16.20 hrs. and 17.10 hrs. and observations confirm those on post- followed feeding. The number of birds copulatory behaviour made on captive present on the pan varied from 20 to 24 birds at Slimbridge by Johnsgard. In one and threat action was most frequently apparently unsuccessful copulation se­ seen at this time. If other birds were near quence he recorded Bill-dipping by the the pair they were threatened and moved male only, so further observations are away. On two occasions the pairs involved necessary to confirm that both birds per­ swam away side by side with heads up form in this way in typical pre-copulatory and breasts slightly raised for a short dis­ behaviour. Once I saw the female White- tance when Bill-dipping commenced. The back Bill-dip twice and stay prone solicit­ female commenced first on one of these ing copulation but the male nearby occasions. Bill-dipping during which the remained with his head up. head is almost completely immersed, was Johnsgard indicates a relationship of repeated once on one occasion and twice the White-backed Duck to the whistling on another, by both birds. On the third ducks. I have seen the complete copula­ occasion copulation was preceded by the tion behaviour in the Fulvous Whistling birds swimming round in a circle with Duck once only. Only the male dipped head and neck on water, and body low. his beak several times without completely Immediately following Bill-dipping be­ immersing his head. Meanwhile the haviour the female swam low in the water female remained with head up on extend­ with head forward. On one occasion she ed neck and moved as though to hinder swam thus round the male. Copulation the male so that his dips alternated from followed with some splashing caused by one side of her to the other. I have seen the beating of the male’s wings. similar behaviour in the White-faced Only two post-copulation displays were Whistling Duck Dendrocygna viduata but seen, one display being interrupted by a copulation did not follow. Coot. On these occasions both birds per­ At the time of these observations the formed the Step-dance, treading water pan was not more than two feet deep at with bodies erect and one wing fully any point and the incidents took place displayed. Observation was made at a more than forty yards from the shore. distance but it would appear that the wing It would seem that the conditions were away from the other bird was raised. On suitable for breeding but it was the dry one occasion, whilst treading water, the season and the pan level was dropping. male bowed forward three times, almost During September the numbers present touching the water with his beak. The dropped steadily and by the middle of female may have done this also. In one October, when the water was not more case both birds remained motionless with than nine inches deep, the Whiteback had heads up for ten seconds following tread­ all left.

Summary The habits and behaviour, characteristic of the White-backed Duck Thtdassomis leuconotus, are described including features associated with resting, feeding, flight, the voice and comfort movements. Types of threat display are described as weÚ as limited observations on copulation.

References c l a n c e y , p. a . 1967. The Game Birds of Southern Africa. Cape Town: Purnell. johnsgard, p. a. 1967. Observations on the behaviour and relationships of the White-backed Duck and Stiff-tailed Ducks. Wildfowl Trust Ann. Rep. 18 : 98-107. McKinney, F. 1965. The comfort movements of Anatidae. Behaviour 25 : 120-220.

A. Clark, 22 Ronketti Circle, Petersfield, Springs, Transvaal, South Africa.