Conserving Montana's sagebrush highway: long distance migration in sage-grouse
Landscape conservation is the mechanism for conserving migratory wildlife in sagebrush ecosystems. We study further a greater sage-grouse (Centrocercus urophasianus; hereafter ‘sage-grouse’) population with the longest-known annual migration, a 240-km journey between summer range in north central Montana, USA, and Saskatchewan, Canada, to winter range north of the Missouri River. We learned more about grouse migration by asking: Do birds fly quickly through a corridor, or do they use stopover habitats within a larger migratory pathway? New GPS-tracking technology revealed that migrating grouse frequent stopover habitats along multiple routes that coalesce to form an integrated pathway. A month-long fall migration in November was in contrast to a punctuated spring migration that lasted on average 2 weeks in late March/early April. Individual birds typically spent ~1 day at nine different stopovers, migrating 71-91 km in 11-15 days. Grouse migrated through gently rolling sagebrush flats (<5% slope), using native sagebrush rangeland in proportion to its availability, and avoiding cropland and badlands where food was scarce. Birds responded to record-breaking snowfall in winter 2011 (>274 cm) by extending their migration another ≤50 km south onto windswept ridge tops where sagebrush remained above snow. Grouse secured food resources by selecting the most similar habitat available on Charles M. Russell National Wildlife Refuge, and doing so was without consequence to winter survival; such was not the case for a nearby resident population. In spring, they made a mass exodus back north, and returned to summer range after migrating ~160 km in 18 days. Previously identified ranges remain important in most years but newly identified winter range suggests that high site fidelity is tempered by an ability to adapt quickly when resources become scarce. Ranching is a compatible land use that maintains this migratory population. We recommend a public land policy that provides grazing opportunities while precluding large-scale energy development or the whole scale removal of sagebrush to increase forage production. Management actions that maintain sagebrush as an emergency food source in newly identified sage-grouse wintering grounds will help to conserve this migratory population. Conservation easements provide a mechanism for maintaining privately-owned working ranches as a compatible and desirable alternative to sodbusting or subdivision along a sage-grouse migration pathway.
© Copyright 2012 Rebecca Elizabeth Smith