[Slow motion of two male sharp-tailed grouse in battle. One jumps on the other’s head as they both flap their wings. The second pecks at the first’s head before they both leap into the air. They land and jump again, with the first getting a good grip on the other’s head with its feet and beak, twisting before they both fall to the ground. They hold their wings out, then jump to attack each other again. One pecks at the other’s face, and comes away with a feather in his beak. They continue jumping up and onto each other. They hold their wings out again, and one grabs hold of the other’s wing feather and pulls while flapping his wings.] 

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Sharp-tailed Grouse square off in intense battles for territory and breeding rights. Male grouse form mating arenas, or leks, where they congregate to compete for small territories and perform mating displays for visiting females. This crowded arrangement leads to continual fighting as the males strive to outdo each other. In most populations, only a few top males are chosen as suitable mates by the receptive females. In this mating system, called lek polygyny, females leave the lek after mating and rear their young without male assistance. In environments where females and resources are difficult to simultaneously defend, and where a male’s parental care does not contribute to the welfare of offspring, lek polygyny is an effective mating system.