Courtship isn't a private affair for the greater prairie chicken and some other bird species. Each spring, males gather in a riot of hooting, stomping, and flapping. This testosterone-laden commotion--known as a lek--attracts females, who scout for a good mate. Now a study suggests that leks may provide another benefit for the birds by lowering the odds of getting picked off by a predator.
It's no surprise that predators might check out the lek. Both the prairie chicken and the sharp-tailed grouse, for example, inflate colorful air sacs on their necks, stamp their feet, spread their wings and tails, and make booming sounds that can attract coyotes and raptors as well as females.
Behavioral ecologist Robert Gibson of the University of Nebraska, Lincoln, witnessed this firsthand when golden eagles attacked lekking sage grouse he was researching in California. Because many types of birds regularly flock when foraging or roosting to feel safer amongst a watchful crowd, he figured, perhaps birds form leks for the same reason. So when he learned that prairie chickens and sharp-tails sometimes lek together, Gibson saw an opportunity to test the idea. He and two colleagues observed mixed-species leks and pure leks of each species in the Nebraska Sandhills.
Females of each species attend leks in proportion to the number of males of their own species there, they found, suggesting that males gain no mating benefit by joining mixed-species groups. Yet many males still choose to join mixed leks. And this mingling isn't accidental, Gibson argues, noting that the two species are not simply forced together by limitation of suitable habitat. A clue to the mixed leks is that the male prairie chickens were more likely to join sharp-tail leks than vice versa. Because sharp-tails spend more time watching for predators, prairie chickens may join leks to benefit from the association, the researchers say. The study is published online this week in the Proceedings of the Royal Society BM.
Predation risk likely does cause some birds to form leks, agrees behavioral ecologist Jacob Höglund of Uppsala University in Sweden, but it is probably only one of many factors involved. Höglund adds that the study would be stronger had it included data or experiments on how the birds respond to attacks, but he acknowledges that at a lek, such violence is a lot harder to observe than sex.