Masters Thesis

Sage grouse nesting habitat in northeastern California

I studied sage grouse (Centrocercus urophasianus) nesting habitat from mid-March through mid-August of 1998-2000 in eastern Lassen County, California. I located nest sites of forty-five radio-marked hens. To evaluate habitat selection I measured vegetation at each nest site and at random sites. Sage grouse avoided low sagebrush (Artemisia arbuscula) cover type for nesting. They used big sagebrush (Artemisia tridentata) cover type and mixed shrub cover type in proportion to their availability. In addition, grouse used diverse sites for nesting as indicated by among nest site variation being similar to variation between nest and random site variables. Likewise, there were habitat differences between successful nests and unsuccessful nests. Mean nest-lek distance was greater for successful nests (x̄=3588 m, SE=811, n=20, P=0.06) than the nest-lek distance for unsuccessful nests (x̄=1964 m, SE=386, n=20). Rock cover was greater at successful nests (x̄=27.67%, SE=4.6%, P=0.04) than at unsuccessful nests (x̄=14.49%, SE=3.04%). Total shrub height was greater at successful nests (x̄=65.5 cm, SE=4.7, P<0.01) than unsuccessful nests (x̄=49.2 cm, SE=1.7). The height of visual obstruction was greater at successful nests (x̄=40.2 cm, SE=2.6, P=0.02) than at unsuccessful nests (x̄=32.5 cm, SE=2.0). Greater distance from the lek, total shrub height, rock cover, and visual obstruction appeared to characterize successful nests compared to unsuccessful nests. My results suggest that rangeland managers should strive for both landscape and microsite heterogeneity.

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