Display Inventory of the Torrent Duck
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Display inventory of the Torrent Duck JAN L. ELDRIDGE Introduction Display inventory The Torrent Duck Merganetta armata is one Male and female Torrent Ducks have a of the least studied species in the family similar display repertoire and, although their Anatidae. Unlike most waterfowl. Torrent vocalizations differ in that the calls of males Ducks are difficult to keep in captivity and are primarily clear-toned and those of consequently little is known about their dis females are harsh, both sexes stress a similar play repertoire. A number of Torrent Duck frequency range (3-5 kHz) which is above displays have been described (Phillips 1953; the background noise of the rapids (0-1-5 Scott 1954; Johnson 1963; Wright 1965; kH z). Johnsgard 1966; Moffett 1970) but no P o in tin g , a series of evenly spaced attempt has been made to study the displays horizontal thrusts of the head and neck is systematically. A basic display description performed commonly by males and females. can serve to illuminate the relations between Both sexes often call just after the peak of individual races of Torrent Ducks and to the head thrust as the head is withdrawn. indicate phylogenetic relationships within the The male whistles a single clear ‘wheet’ family Anatidae (ef. Heinroth 1911; Lorenz (Johnsgard 1966) and the female emits a 1941; Delacour & Mayr 1945; Johnsgard throaty ‘queech’ (Figure 1-2). These were 1960, 1961a, 1965). the most common calls heard during daily In this paper displays are taken to be activities and aggressive interactions. The ritualized behaviour patterns .. ‘those male’s whistle carried well over the rapids peculiarly standardized and often but the female’s call was easily lost in the exaggerated performances including all background roar. vocalizations and many movements and All moves, including flight, swimming, or postures, which have become specialized and position changes, such as jumping off an modified as social signals or releasers' emergent rock, were preceded by Pointing. (Moynihan 1955). The terminology for com The small (minimum neck extension) and fort movements is that of McKinney (1965). irregularly spaced head thrusts appeared to aid in judging distance. Undisturbed, upriver flights were preceded by a long sequence of M ethods Pointing which began with a few, irregularly spaced head thrusts involving little neck The following observations deal primarily extension. The body stance was relaxed and with one pair (M 1/F 1) of the southern sub somewhat hunched (Figure 3a). Gradually, species, Merganetta armata armata , that the bird became more erect and the head resided in the lake district on Rio Nalcus, thrusts evenly spaced and more rapid with Osorno, Chile, in the austral spring of 1975. greater neck extension (Figure 3b—c). Often Additional observations on an upriver pair several minutes elapsed before flight and the (M2/F2) and a pair on Rio Chanleufue have birds moved from rock to rock Pointing as been included. Both rivers had swift, highly they swam. M 1 and F 1 often called while oxygenated, clear, cold water that moved in giving the emphatic head thrusts before flight an area of rapids over a substratum of rock, and both vocalized during flight in a call- stones and gravel with only limited areas of response pattern which probably served to sand and silt, characterized as rhithron in maintain contact (‘queech-wheet’ ... ‘wheet- nature by Hynes (1970). During the study, queech’ ... ‘queech-wheet’). individual males were identified by variations Pointing was also performed by seemingly in the black and white feather pattern of the wary birds. The head thrusts were directed at head and neck. Individual females could be an angle of 30° to 45° above horizontal and identified by missing tail feathers which are each fully extended thrust was held in a molted throughout the year (Weller, 1968). ‘craning’ post with neck, head, and body The drawings are based on super-8 mm feathers sleeked. Points could also be films exposed at 24 frames per second. The associated with rapid, cursory nibble-preens sonograms of vocalizations were made from when a bird was frightened or wary; each cassette recordings. Point alternated with a brief preen, usually of Wildfowl 30 (1979): 5-15 5 6 Jan L. Eldridge TIME IN SECONDS Figure 1. Vocalizations by the territorial pair: male 'wheeow' with an extended Point (a, b), female ‘queech’ followed by male ‘wheeow’ in characteristic call-response pattern (c, d), female ‘queech' followed by male ascending ‘warble’ (e), repeated female ‘queech’ calls followed by her mate's repeated ‘wheet’ calls (I), male ‘warble’ call (g), and male repeated ‘whee’ (h). The calls are redrawn from sonograms with the river noise indicated by horizontal lines. the upper belly. The body was hunched, the interactions calls were so commonly given feathers ruffled, and each Point and preen with Pointing that they formed a background sequence occurred in less than a second. In noise (Point-wheet... Point-queech ... etc.). the water, a wary bird often swam with its During tense confrontations, when rival tail resting on the surface, Pointing with males stood near each other on emergent exaggerated head thrusts and sleeked head rocks, the territorial male often performed and neck plumage. slow, scooping head-thrusts lateral to the Pointing occurred almost continuously rival. Each thrust was angled 45° to 60° during aggressive interactions but the head above horizontal and was held briefly at full thrusts varied in neck extension and thrust neck extension (Figure 4b). Each head thrust rapidity (Figure 4a-d). FI, for example, appeared to be an individual performance averaged 1-4 head thrusts per second during rather than part of a series. Often the scoops 630 filmed seconds of aggressive interaction. alternated first to the left and then to the Most head thrusts were either in the direction right, 10° to 20° off centre. Each scoop was that the bird eventually went or toward a usually associated with a ‘wheeow’ call rival (Figure 4a). For example, a bird might rather than a ‘wheet’ (Figure la-b). The Point toward an emergent rock, then it stressed frequencies (4-5 kHz) were would jump into the stream, swim to the preceded by an ascending slur and ter rock and then Point at the rival. minated by a descending slur. A call- Often a Point by one bird immediately response pattern occurred between mates, followed one by its mate. During aggressive the male giving an extended head thrust and Torrent Duck display i TIME IN SECONDS Figure 2. Vocalizations of the territorial pair: two female ‘queech’ calls and one 'gaga-brr' followed by male’s ‘warble’ (a), male ‘warble’ calls (b, c, d), male ‘warble’ call near nest (e), and male ‘wheet' near nest (f). All calls are redrawn from sonograms with the river noise indicated in horizontal lines. ‘wheeow’ call, the female giving a typical Pointed as it swam thrusting the head head thrust with ‘queech’ call (Figure Ie—d). forward alternately to the right and left 10° In an Upright posture, originally described to 20° off centre causing the bird to progress by Scott (1954), the bird holds its body erect, on a zig-zagging course. feet widely spaced, and bill horizontal. Males The Upright was usually associated with erect their crest and cheek feathers Pointing although the birds called ‘wheet’ or emphasizing the black and white striations ‘queech’ without Pointing while in this on the head and neck and drop their wings stance. In addition, the male whistled revealing the horn grey spur and exposing repeatedly in a series of slightly ascending the specula. The posture was characteristic then descending notes. Each note appeared of aggressive interactions and was assumed similar to the ‘wheet’ vocalization in frequen by territorial owners and intruders of both cy but lacked the trailing finish (Figure sexes. When a bird moved from rock to rock 1 h). Early in an aggressive interaction, just during a confrontation it assumed an after the intruders were discovered, F 1 Upright on each rock and swam in an erect emitted intense, repeated ‘queech’ vocal posture with head and neck held back and izations in an Upright and M l, also in an tail fanned above the water surface. Often it Upright, responded with repeated ‘wheet’ Jan L. Eldridge P t ' p - /r>-ñ - f ? - f f f t f 1 )( Y )í ■ b / 1 - Ü ■ ' ■ 'CV V' ' J X X J. J J J J J J J <1 2 3 4 5 6 7 8 9 10 11 f i (=j s?? T> Figure 3. Three sections from one female pre-flight Pointing sequence that resulted in flight showing (a) % IX A ! :___ preliminary head thrusts, (b) intermediate, and (c) greater neck extension and more erect stance before flight. The numbered line indicates the frame used in Figure 4. Pointing by the territorial pair during each section. aggressive interactions in four film sequences: male Pointing in Upright (a), male extended Pointing in Upright (b), male Pointing while swimming with the calls that matched the rate of the female’s raised tail (c), and female Pointing while B arging(d). call (Figure 10- Drawings in each sequence were made from con When two rival males faced each other secutive frames. during an interaction, the territorial male stood in an Upright and deliberately turned his head, with bill horizontal, so that one (Figure 4d). FI often made short distance cheek was toward the intruder. After less Barges toward the intruder, rising extremely than a minute he would methodically turn his high in the water and Pointing rapidly. M 1 head again to face the intruder directly. often leaped after her and approached the in B arging varies from a relatively fast and truders.