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.