Mike Smith wrote:

>Since when are blackbirds 'nice'? Male Red-wingeds seem to 'rape'
>females as well. I saw 2 males chase a female around a marsh until she
>was too tired to get away, they all disappeared into a bush for awhile.
>I don't know if she ended up copulating with both males or not. But it
>seems an amorous-feeling Red-wing will sometimes not take 'no' for an answer.

Nature is a lot more complex than most people realize, and in particular
social behavior can be surprisingly varied. Monogamy is the rule in birds,
but it's a rule meant to be broken. Males of a surprisingly large number
of monogamous species that have been studied well are known to be quite
alert to the presence of a female unguarded by her mate, and a bit of
dallying may ensue (pardon my anthropomorphism; I'm going for spicy
writing). More genes in the next generation is the male's reward.

What makes it less of a one-sided picture is that the females, in some
cases, are more than willing. In this case, *better* genes in the next
generation is the female's reward, assuming the intruding male is really
hot stuff (= more fit in one or more traits). To continue the
anthropomorphic vein, even if he's not more fit per se, if the female
accepts his "playboy" genes and has "playboy" young that her unsuspecting
but dependable mate helps her rear, and if *those* young then go on and
fertilize more than their share of females, guess what? Both the "playboy"
genes of the male and the "playboy-susceptible" genes of the female
increase. See how it works?

In birds that breed in large numbers in a relatively small space, the
interactions get even more intense. A female Red-winged Blackbird flying
to and from her nest has to do it as quickly as she can, as any male the
territory of which she passes through will attempt to copulate with her.
Check out a red-wing colony and see how many "sexual chases" there are.
And it's not always in vain. In one study, some of the males in a marsh
were vasectomized, and a surprisingly large number of their females laid
fertile eggs. You figure it out.

And that's tame compared with Cliff Swallow society. A Cliff Swallow
colony has the complexity of social interactions of a Malibu Beach condo.

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