This Video Shows A Great Blue Heron Inhaling Its Prey

July 18, 2014 3:41 PM

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Ninety-seven percent of bird species don't grow penises. But why? A 2013 study that compared chickens (who don't have penises) with ducks (whose penises are "large and elaborately coiled," according to one description) found that a sort of cell suicide, called "programmed cell death," is to blame. “Evolution comes down to reproductive fitness," Martin Cohn, a University of Florida biologist, told the Los Angeles Times. "So it’s remarkable that a group of animals would eliminate a structure that’s so important for reproduction.” A theory as to why birds lost their penises is that female birds may have preferred it, since, as The Scientist put it, birds of this disposition "are less capable of unwanted advances and thus give female birds more choice in which males father their young."

For those birds without penises, mating takes the form of the "cloacal kiss." The cloaca is an orifice found on the rear of both bird sexes. It serves a whole bunch of functions: pooping, peeing, egg-laying, and sperm ejection. When it's time to mate, the cloaca will swell. The male and female birds...

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