the sex lives of birds -- 8/5/20
Today's selection -- from The Bird Way by Jennifer Ackerman. The sex lives of birds:
"I've always loved the refined look of male mallards, their shiny iridescent green heads ringed by a narrow white band, and those crisp violet speculum patches fringed in white on the wing. But unmated males among these dabbling ducks have a well-deserved reputation for truly dreadful mating behavior. Groups of drakes may force themselves on an unwilling female, sometimes attacking with such violence and in such numbers that they kill her in the process. Wood ducks are also known for this brutal practice, dozens of males try to mate with a single female.
"Contrast this with the billing of Atlantic puffins, a gentle rubbing together of beaks in anticipation of sex. Or the sweet-seeming presentations of flower petals by male superb fairy-wrens. Or the tender mutual attentions of Fischer's lovebirds, those vibrant pint-size parrots native to Tanzania that gave us our expression for openly affectionate couples. Lovebird pairs snuggle, gently preen each other, and nibble beaks, the bird equivalent of kissing. After separation or stress, they feed each other to affirm their bond. When a male approaches his mate, he sidles back and forth energetically, bobbing his head up and down, twittering, and then regurgitates some food into her mouth. If a mate dies or disappears, the other partner will pine for it. This is true, too, for mated pairs of those maligned mallards. When they form pair-bonds, they stay together for the season and solidify their bonds with precopulatory displays of head bobbing, nodding, and shaking.
"For sheer variety, the sex lives of different bird species are hard to beat. At first blush, their reproductive organs seem all alike. Both male and female have a cloaca, an opening that in the male swells during the mating season, projecting outside their bodies. When birds mate, they briefly rub together their swollen cloacae, allowing the male's sperm to move from his cloaca to hers and then travel up her reproductive tract to fertilize her egg. (Bird cloacae also have a decidedly less sexy role: to excrete urine and feces.)
|Superb fairy wren with flower|
"Most birds have no penis. But there are exceptions. Several species of ducks, geese, and swans have an organ like a human penis, which is inserted into the female. These waterfowl belong to the 3 percent of living bird species that retain the phallus found in their reptilian ancestors. Some ducks -- such as those brutish male mallards -- have impressive counterclockwise corkscrew-shaped, snakelike phalluses that grow as long as their bodies, which they use to deposit sperm as far as possible inside the female reproductive tract, to better their chances of fertilizing her eggs. The length correlates with the degree of forced copulation that males impose on female ducks, says biologist Patricia Brennan.
"It's the evolutionary upshot of a sexual arms race. Until recently, all the focus had been on the duck penis, but really -- as Brennan discovered -- this anatomical story is a story of female agency, even in the face of extreme sexual violence. Brennan has found that females have evolved their own rococo genitals, a spiral-like reproductive tract that winds clockwise, in the opposite direction from the male's penis, and includes up to three branches with blind pockets that make it harder for sperm to reach her eggs. 'Female mallards have a say in which sperm fertilize their eggs,' she says. 'As many as 35 percent of all copulations with a mallard female are forced by unwanted males, yet these males sire only 3 percent to 5 percent of her offspring.' With a forced copulation, the female keeps her genital tract tight, blocking the male's lengthy phallus or forcing it to divert down one of those dead-end alleys, so his sperm can't fertilize her eggs. If she actually wants to mate with her partner, she can relax the walls of the tract and allow his semen passage. She can also eject sperm from her cloaca by defecating right after sex.
"As for the act itself, many birds copulate quickly for only a second or two, a 'cloacal kiss' that effectively transfers sperm. Notable exceptions include the red-billed buffalo-weaver and the aquatic warbler, which may couple for more than a half hour. The male warbler 'clings to the female's back so that the pair hop around together in the vegetation like a couple of mice,' writes British ornithologist Tim Birkhead. The vasa parrot, a native of Madagascar and the nearby Comoros islands, may hold some sort of record. One pair was observed copulating for a full 104 minutes, cloacae locked together, the male's tail curled up under the female's tail, her wing extended over his body.
"Some birds copulate just once, achieving fertilization in one quick go, while goshawks couple as many as six hundred times for a single clutch of eggs. Why so many tries? If you're a bird of prey and have to spend long periods hunting, away from your mate, it's harder to guard her from having sex with other males. Multiple matings may dilute any semen acquired from other males in your absence.
"Most birds do the deed out in the open, on a nest or patch of ground or branch or, occasionally, in the case of oxpeckers, on the back of another animal, like an African buffalo. Common swifts, birds that spend nearly their entire lives aloft, eating and sleeping on the wing, mate mostly at the nest, but have been known on occasion to copulate in flight, male just above and behind the female. Gulls do it on the beach.
"By contrast, Arabian babblers often go to great lengths to hide the act of sex, copulating out of sight of their group members, just as humans do."