The word lek is from the Swedish verb leka, meaning to play. In ornithology it denotes an area consisting of a number of display territories, or "dancing grounds," where male grouse carry out their courtship dances and mate with females generation after generation. With tail erect and fanned, and with rigid wings almost touching the ground, the cock inflates a sac in his throat until it hides his head, and the fleshy chambers of the sac protrude. By inhaling and exhaling rapidly the bird produces a resonant booming sound.
Birds on the Brink
We may now summarize Lewis and Clark's observations, supplement them with a few modern interpretations, and come up with reasons for the decline of sage grouse as well as what might be done to reverse it. Five points stand out: 1) Being large birds, sage grouse are typically long-lived with comparatively low reproductive rates. This makes them especially vulnerable to predation. 2) Sage grouse evade predation by camouflage, and by remaining hidden under dense cover. 3) Because their diet is restricted to soft foods, they have evolved nonmuscular gizzards. 4) Sage grouse are solely and absolutely dependent on big sagebrush for food, as well as cover. 5) Sage grouse are very faithful to established lek locations. Sage grouse populations have declined as each of these components has been compromised.
A field of Sagebrush in the Beaverhead Valley
Sage grouse are entirely dependent on sagebrush during winter, when snow depths are generally shallower in sagebrush zones. The field pictured possibly consists of Artemisia tridentata, big sagebrush. However, the differences among many of the seventeen different species of the genus Artemisia in the U.S. are so difficult to distinguish that even experienced botanists are challenged.
Big sagebrush habitats have been eliminated on a broad scale. Most of the ancient stands in the Columbia river basin have been converted to wheat fields, which make fine food for pheasants,3 but sage grouse cannot digest grains. In the inland west sagebrush has been destroyed by herbicides, or else burned to expand hay production or in the erroneous belief that it would improve grasses for cattle grazing. In some areas, the prevention of periodic natural fires has allowed invasions of trees such as junipers. The elimination of the big sagebrush habitat has been a major cause of sage grouse decline.
Sage grouse predators have become more successful. Construction of power lines and fences across sage grouse habitats has provided perches for avian predators to observe and capture sage grouse. The proliferation of red foxes and the introduction of domestic dogs have compounded the problem. Overgrazing has reduced the density of inter-shrub grasses and forbs, and sagebrush has deteriorated, all reducing cover and increasing sage grouse exposure to predation.
Sometimes historic leks have been deliberately but thoughtlessly destroyed. In one instance a lek was flooded to create a holding pond, and grouse were seen to be attempting mating dances on the ice above it—unsuccessfully. In another case grouse were observed attempting displays on a roadway covering a historic lek, causing some to be killed by traffic. Interference with mating behavior is a very effective way to induce population decline. Coalbed methane extraction in big sagebrush country may be the last nail in the sage grouse's coffin. Even worse than the impacts of access roads and drilling pads is the need to pump water into a coalbed to force out the methane. The water table concentrates underground salt, which sterilizes the soil, killing all vegetation, including sagebrush. Finally, ponds of water create breeding grounds for mosquitoes, including some that carry west-Nile virus, which has been shown to be fatal to sage grouse.
We know what actions would reverse the decline of sage grouse in America. Hopefully, we will find the will and the means to apply them.
3. The scientist's name for the common pheasant is Phasianus (fayz-ee-AY-nus; see note 1, above) colchicus (COAL-chee-kus; from the ancient Greek province of Colchis, where the Phasis River flowed). Sometimes called the Chinese pheasant, or—owing to the prominent white ring around its neck—the ring-necked pheasant, it was introduced into North America in the late 19th century. It is the state bird of South Dakota.
Supported in part by a grant from the Montana Committee for the Humanities