Over at Death's Door, there is a certain degree of consternation about the possibility that mallard ducks would be gang raping each other.
There is a bunch of confusion wrapped around that so let's start slow.
I also wasn’t aware that duck’s had duck cocks to gangbang with. I never eaten a duck but I’ve eaten a lot of chicken, and when you buy the chicken in the store and pull out that little pouch of giblets and shit, I’ve never seen a tiny chicken cock sittin off in there.
So, what do duck dicks look like, and why don't you see genitalia in chickens from the store?
Most birds copulate without a penis. The male essentially just rubs the sperm over female genitalia, and fertilization ensues. Some species (waterfowl like ducks and swans, ostriches and their relatives, and some South American species) have a structure that penetrates the female cloaca. It isn't really homologous to a penis since it seems just to act as a guide for the sperm. This paper describes a 20 cm (not mm) long duck penis with spines (PDF with images). The spines are not typical, and 50mm is apparently closer to normal for a duck. The 50 mm penis would be a couple inches long in a bird that is about 2 feet long. I'll let you do your own math to a more familiar scale. (updated 12/2/2005: This said 20 mm for over a year before someone caught the error. Oops!)
As for rape, the answer is yes. A couple years back, there was this fascinating article published in the Netherlands, describing homosexual necrophiliac rape in mallards. One duck had been chasing another in an attempt to rape it, when the chasee flew into a window and died. For over an hour after that, the other duck engaged in near constant copulation before a scientist could recover the remains for science.
The article notes that people who pay more attention to ducks than I do see groups as large as a dozen ducks chasing one female and then serially raping her.
It also points out that wild populations of ducks find 2-19% of mallard pairs are same sex. I've found no data on whether homosexual ducks are more common in red states or blue states, but I'd watch for new laws about aberrant ducks in time for the next election.