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This is the last of what turned into a series on the female impersonators of the animal kingdom: males that temporarily or permanently mimic the females of their respective species to enhance their mating opportunities. Cuttlefish do it, as do isopods, a whole slew of fish, one snake, a couple of lizards, and at least two birds. (If the phenomenon occurs among mammals, I haven’t located any examples.) One of the birds is the western marsh-harrier, in which 40 percent of males have female-typical plumage and are not recognized as rivals by “normal” males. The other, better-known species is the ruff (Philomachus pugnax), which has a much more complicated arrangement. The Latin name translates as “combative battle-lover.” 

The ruff is a kind of sandpiper, about the size of a dowitcher. Although native to Eurasia, it occasionally shows up in California during migration. I’ve seen three or four individuals here, including one that visited what I didn’t realize beforehand was a gay men’s nude beach near Davenport. That was awkward. Anyway, a fall ruff is nothing special to look at. Spring is when they live up to their name: most males grow an imposing, Elizabethan-style neck ruff, the color of which indicates an individual’s courtship strategy. 

Like a number of other birds—prairie-chickens, some birds of paradise, manakins—ruffs are lekkers. A lek is the arena where multiple males display to attract females, who drop in to mate with their favorites. (Remember Werner Herzog’s documentary Herdsmen of the Sun about the Woodabe people of Niger, whose young men doll themselves up and perform a mass dance for the young women?) Mating is the end of the male’s participation; females go off, build a nest, and rear the young on their own. Multiple male ruffs gather at favored spots in the spring, in open grassy areas. Those whose neck ruffs are reddish-brown, black, or some barred or brindled combination select territories (this is where the pugnax comes in.) A resident males are accompanied by satellite males with white ruff feathers who hang out in the periphery of his territory. The ratio of residents to satellites is about six to one. 

Ornithologists have spent decades watching ruff leks and figuring out what’s going on. Some, like David Lank of Simon Fraser University in British Columbia, have reared captive flocks and used genetic analysis to determine the paternity of chicks. They’ve found that females (called reeves) typically mate with more than one male. Although residents get more action, some females choose to mate with white-ruffed satellites. Field studies have shown that females are more prone to visit territories with larger numbers of satellite males. Lekking males also mount other males; not for nothing has lek behavior been called “orgiastic.” 

It was only about five years ago that a third type of male was recognized. Bird-banders had noticed that some female-plumaged ruffs were intermediate in wing length between typical males and females. Two Dutch ornithologists, Joop Jukema and Theunis Piersma, discovered that these birds were in fact males, with a mating strategy of their own. They dubbed them “faeders,” from an Anglo-Saxon word for “father,” although their behavior is no more parental than that of residents or satellites: they’re all just sperm donors. Faeders are sneakers, like Type II midshipman fish and beta and gamma isopods, using their resemblance to females to fool resident males. And like those creatures, they invest heavily in sperm production; the testes of faeders are 2.5 times larger in volume than those of “normal” males. Jukema and Theunis estimate that only about one percent of males are faeders. 

As you might expect, the genetics behind all this are interesting. The difference between residents and satellites is based on a stretch of a non-sex chromosome. That means that both sexes carry both forms of the gene. Females given testosterone implants assume either resident or satellite characteristics. It’s not clear from what I’ve read how the faeder morph fits in. 

Haldane was right: the natural world isn’t just stranger than we imagine; it’s stranger than we can imagine.