To continue the thread about skewed sex ratios and forced copulation:

I once watched 10 male American Wigeons chasing a female around and around
Green Lake in rapid, twisting flight. Every once in a while she'd land
(tired?), and males would frantically do courtship displays at her and each
other, then one would attempt to copulate and she'd fly up again, and the
whole thing would be repeated. "Frenzy" was the only word that described
it. Anthropomorphically, I felt sorry for the female, but it is
well-placed sympathy, as their health and even lives are obviously
threatened by this activity.

As Jon wrote, well into the spring or early summer is the time to see a lot
of this. There are always a fair number of unmated male ducks around, as
the sex ratio is skewed, we think because female mortality is higher
because they are taken by predators while incubating. These males become
increasingly motivated to mate, as Kathleen wrote, not because they know
what the consequences of mating are, but because they are genetically
programmed in a way that causes their hormonal levels to rise, which in
turn makes them intensely directed to copulate with a female of their own
species. If they don't have a mate, any accessible female will do.
Presumably the reason ducks pair (and copulate, long before egg-laying
[know any other species that separates copulation from reproduction?]) so
early in the winter compared with most other birds is that males are
attempting to monopolize one of those rare resources, a female. In
migratory ducks (which includes most of them), the male then accompanies
the female back to her breeding grounds.

Because of this winter mating, ducks have to recognize potential mates in
big mixed-species flocks, and this is probably why the males have diverged
so much from one another in both plumage characters and courtship displays.
Beginners who feel good about being to identify all the ducks in the area
should thank the coyotes that cause the female mortality that causes the
skewed sex ratio that causes the winter mating that causes the distinctive
male plumages!

It is really different in Argentina. The ducks down there, many of them
closely related to our species, are nonmigratory and monogamous; everywhere
you see pairs together with their offspring. Most lack sexual dimorphism,
as there aren't the migratory flocks in which pairing takes place. The
interaction among evolution, ecology, and behavior couldn't be more clear.

All this stuff is going on out there, in every wetland, as we write these
notes. "Look and you shall see" should be the first axiom of birdwatching.
A better one for us to emphasize, IMHO, than "call the hot line and you
shall look."

Dennis Paulson phone: (206) 756-3798
Slater Museum of Natural History fax: (206) 756-3352
University of Puget Sound e-mail: dpaulson at ups.edu
Tacoma, WA 98416