On the move
Most of the time, Greater sage-grouse get around by walking, but they are strong fliers over short distances when they have to move to escape threats in their immediate surroundings. When the threat involves longer-term shortage of food or cover, the birds may migrate.
An ongoing study in Montana is filling in significant gaps in what we know about the routes sage-grouse use to migrate from one preferred habitat to another.
Other studies show that populations in Idaho on the Upper Snake River Plain (centered on Dubois, Idaho) and the Browns Bench area (south of Twin Falls, Idaho) migrate significant distances. Sage-grouse on the Upper Snake plain move an average of 66 straight-line miles annually over a range of at least 1,065 square miles.
The BLM is using data from Browns Bench collected between 2002 and 2010 (open map.PDF) as part of an environmental impact statement (EIS) analyzing the cumulative effects of energy development and livestock grazing on sage-grouse habitat in the Shoshone Basin.
The photo at-right shows researchers attaching a radio collar that transmits GPS data on a particular bird's position at regular intervals. Birds seldom move in the straight lines that connect their position points on maps, but the straight-line mileage between 2 position points gives a minimum estimate of migration distance.
Creatures of habit
The range and migration patterns of sage-grouse on the Upper Snake River Plain have remained essentially the same since the 1950s. These observations about migration also help explain why sage-grouse need large, interconnected expanses of sage-steppe habitat.
Sage-grouse may migrate away from leks and nesting areas in non-breeding seasons but will return year after year to strut, breed and rear their young in familiar places. This is more than a preference – sage-grouse show little ability to find and utilize new habitats when their traditional areas are disrupted.