Duck Displays
photographs a Mallard (top) and Northern Pintail (bottom) by Rohan Kamath and photograph of a Northern Shoveler (middle) by Tom Grey Most ducks confine their displays to the water (or land) surface, since their heavy weight relative to their wing area ("high wing loading") dictates continuous flapping and makes complex maneuvers, such as hovering and soaring, difficult or impossible. Aerial communication is thus largely restricted to short, ritualized flights (ordinarily close to the water surface) and vocalizations, including contact calls that help maintain flock coherence in these rapid fliers that often go long distances between landings.

Most people's first observations of duck behavior probably are of Mallard courtship. Mallards perform in the fall and winter as well as the spring, so there is plenty of opportunity to watch their displays. They are also often rather tame, and perform in the open -- this is a good thing since, while frequent, their displays are subtle and brief. Males swimming in the presence of females may be seen shaking their heads (head-shake display) and tails (tail-shake), often doing the former with their breasts held clear of the water and their necks outstretched. They also raise their wingtips, heads and tails briefly and then swim with their necks outstretched and held close to the water (head-up-tail-up). Groups of four to five males may swim around females, arching their necks, whistling, then lowering their bills below the water surface and jerking their bills up to their breasts while spurting water toward the preferred female (water-flick or grunt-whistle). The water-flick may take only a fraction of a second to complete. The drakes in male groups give short, nasal "raeb-raeb" (two-syllable) calls, and short high-pitched whistles.

Female Mallards and other female ducks often demonstrate (inciting displays) and call to provoke males to attack other males or females. In some circumstances these displays may allow the female to observe the performance of males and to evaluate them as potential mates. To elicit displays from a group of males, a female Mallard may swim with her neck outstretched and her head just above the water (nod-swimming). When a strange male approaches a female Mallard, she often will do an inciting display, swimming after her preferred mate while producing a rapid staccato series of quacks and flicking her beak back and downward to the side. As pairs are formed, both sexes may be observed lifting a wing, spreading the feathers to expose

the speculum (the patch of bright color at the trailing edge of the wing), and placing the beak behind the raised wing as if preening. Then just before copulation, the male and female typically float face-to-face and pump their heads up and down.

Similar courtship can be seen in other dabbling or "puddle" ducks (in North America members of the genus Anas -- who are able to spring into the air without running across the water surface). The displays of the Black Duck are, in particular, almost identical with those of the Mallard. Nevertheless, significant differences in patterns of communication exist among members of the genus, differences that have evolved in response to varying ecological situations. Shovelers, for example, are specialized for the time consuming process of sieving plankton from the waters of small, permanent ponds. A male defends a small, discrete territory around his mate, with whom he has a strong, long-lasting relationship; consequently he rarely spends time in "extramarital" pursuits.

Northern Shovelers and their close relatives within the genus Anas (Blue-winged and Cinnamon Teal, Garganey) are known collectively as the "blue-winged ducks" because of their powder-blue or grayish upper-wing coverts. Blue-winged ducks have evolved a conspicuous "hostile pumping" display. The head, with crown feathers depressed and bill slightly elevated, is repeatedly raised high while giving "took" calls out of phase with the pumping. This sequence is used both as a short-distance territorial display ("stay away from my mate/nest") and long-distance territorial threat display ("stay out of my feeding territory").

Unlike relatively sedentary shovelers, pintails (again, a member of the genus Anas) range far and wide to forage in temporary bodies of water, and tend to nest in sparse cover at a great distance from water. In addition, male pintails spend only part of their time with their mates, and devote some of their time trying to copulate with other females; as a result female pintails tend to be frequently harassed. It seems likely that close defense of a territory is profitable for the male shoveler because concentrated food resources allow him to provide an area where his mate can obtain sufficient food free from harassment. No such strategy is feasible for the male pintail because of the dispersed nature of that species' food resources. Therefore Northern Pintails and their relatives (e.g., Green-winged Teal) have not evolved a conspicuous long-range territorial threat display; they need only guard nests and mates, not feeding territories.

This discussion of Mallards, shovelers and pintails only scratches the surface of the complexity and variety of duck displays. For example, Robert Alison studied the displays of Oldsquaw, whose "ahr-ahr-ahroulit" vocalizations are familiar background music to those who have spent time in the northern tundra. He distinguished a dozen distinct displays performed by courting males alone: the lateral head-shaking, bill-tossing, rear end, porpoising, wing-flapping, body-shaking, parachute, breast, turning-the-back-of-the-head, bill-dipping, steaming, and neck-stretching displays. Some of these are accompanied by unique vocalizations. Females, in turn, perform chin-lifting, soliciting, and hunch displays; though the precise functions of these displays are still unclear, they occur with different frequencies in different situations: male-male encounters; male-female encounters; pre- and post-copulation, etc.

The problem of thoroughly analyzing such displays is not trivial. Benjamin Dane (now of Tufts University) and his colleagues studied 22,000 feet of film of displaying Common Goldeneyes. They used a stop-action projector to view each frame individually, counting frames (the film was exposed at a constant 24 frames per second) to determine the duration of a given display. It was thus possible to time each display accurately and to determine the probability of one display following another at each stage of the courtship. The projector was also used to analyze display-response interactions between individuals. One of the most interesting findings was the rather uniform timing of some of the displays -- the head-throw of the Goldeneye took an average of 1.29 seconds to perform, and some 95 percent of head-throws were timed at between 1.13 and 1.44 seconds.

The great complexity of duck courtship displays probably has evolved because ducks tend to concentrate in small areas to breed, and closely related species often give their displays in plain view of each other (and of human observers, which makes them a joy to study). This has created considerable evolutionary pressure for each species to develop distinctive displays, so that hybridization among different species displaying together will be minimized. Thus, for example, the displays of Barrow's Goldeneyes are very different from those of Common Goldeneyes until the precopulatory stage is reached. In spite of this, some hybrids between Barrow's and Common Goldeneyes occur, but with nowhere near the frequency of hybrids between Mallards and Black Ducks, which have very similar displays.

A major problem that needs more investigation is exactly how context affects communication. Does a certain display given by a mated male convey different information from the same display given by a courting male? Does the distance between signaler and receiver influence meaning? How about orientation (face-to-face, side-to-side, etc.)? When and why does consistent alternation of two displays occur?

Recent advances (and price reductions) in portable video cassette recorder systems may open wide the door to advanced analysis of behavior -- all that is needed is the development of appropriate telephoto lenses. With the participation of increasing numbers of birders and ornithologists, the meaning of many of the complex (and often rapidly performed) displays of ducks may be clarified, increasing our understanding of why these displays have evolved.

SEE: Visual Displays; Shorebird Communication; Sexual Selection; Dabblers vs. Divers.
Copyright ® 1988 by Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye.