Greater Sage-grouse

Leonard and I spent Easter weekend hiking in Northern California and Oregon. We had three “quests”: a greater sage-grouse, a silk tassel bush and a great grey owl. We found two of our goals, only the great grey owl continues to elude us.

We found a greater sage-grouse (Centrocercus urophasianus) along Modoc National Forest Road 136 near Clear Lake (Modoc County CA). A resident of the sagebrush steppes centered on the Great Basin in Western United States, the greater sage-grouse is the largest grouse in North America. Greater sage-grouse are generally resident and only move if deep snow prevents them from finding exposed sagebrush during the winter.

Greater sage-grouse are cryptically colored – a patterned brownish that tends to conceal or camouflage them in the grasses and sagebrush of their habitat. Both sexes have a dark belly and long, pointed tail feathers. Males have yellow eye combs, black necks and bibs and a white ruff on the breast. The smaller females have a brown throat and breast.

Greater sage-grouse feed solely on sagebrush leaves in winter and fall, although they also eat the leaves, buds and flowers of forbs (flowering plants) and insects in spring and summer. For the first three weeks after hatching, the chicks cannot digest sagebrush leaves so their diet consists of forbs and insects.

Sagebrush leaves contain terpenes, organic compounds that upset the digestive systems of most animals, and additionally sagebrush leaves are difficult to digest. But the digestive system of a greater sage-grouse is designed to digest sagebrush. When a greater sage-grouse eats a sagebrush leaf it only bites off half the leaf. In most birds the gizzard, a muscular organ, uses the grit a bird eats to grind up seeds and other food. A greater sage-grouse gizzard does not grind up sagebrush leaves. (A greater sage-grouse does not eat grit.) Instead, the sagebrush leaves are simply held in the gizzard where mucous softens the leaf in preparation for digestion. During digestion, the digestive juices enter the leaf through the cut (bit off) end and dissolve the inner parts. What remains is the undigested outer leaf cells. Since terpenes are contained in the outer leaf cells, they are expelled with the undigested half-leaf.

Greater sage-grouse populations are decreasing, mainly because of habitat fragmentation and development. Hunting and predation also contribute to the decline of these interesting birds.

Greater sage-grouse are known for their courtship displays. Maybe if we are lucky, some day Leonard and I may be fortunate enough to observe greater sage-grouse lek (display grounds) behavior.  Then I will discuss this mating activity.

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