Lek is a Swedish word and literally refers to the area where "matrimonial affairs" of animals are carried out; probably elliptically from the Swedish lekställe "mating ground" (Lloyd, Llewelyn. The game birds and wild fowl of Sweden and Norway. F. Warne & Company, 1867). The Greater Sage-Grouse is one of the most well-known birds that exhibit lekking behavior, but many other birds do it too; including: Great Snipe, Manikin, Prairie Chicken, Sharp-tailed Grouse, Musk Duck, Hermit Hummingbird, and Peacocks. Mammals, reptiles, insects, and fish also have species that lek.

A lek is an aggregation of males that gather to engage in competitive displays that may entice visiting females who are surveying prospective partners for copulation (Fiske, P., Rintamaki, P. T. & Karvonen, E. Mating success in lekking males: a meta-analysis. Behavioral Ecology 9, 328–338, 1998).

Greater Sage-Grouse return to the same leks year after year, like salmon returning to their spawning grounds. In fact, some leks may have been the site of the sage-grouse's elaborate springtime courtship display for thousands of years. The loss of a lek, to flooding, agriculture or energy development, or other habitat destruction, has profound consequences for the grouse who return to it each year.

The Greater Sage-Grouse display is among the most complex of bird mating rituals. Dozens of males strut, fan their tail features, and pop the yellow air sacs on their breasts to create a "wup" sound that can be heard two miles away. Beginning around dawn, and peaking in intensity at the time of the full moon, males display for three to four hours. A single male may mate with 20 females in one morning. All this activity requires a lot of energy, and males lose a significant amount of body weight during breeding season.

The annual event has inspired the Grouse Dance performed by several Plains tribes of Native Americans, in which drums imitate the rhythms of the male sage-grouses' air sacs.

(Photo by Ronan Donovan)