Sage-grouse (Centrocercus urophasianus) nesting and brood-rearing sagebrush habitat characteristics in Montana and Wyoming

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2005

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Montana State University - Bozeman, College of Agriculture

Abstract

Nesting and brood-rearing habitat data for greater sage-grouse (Centrocercus urophasianus) near Roundup in central Montana in 2004, Decker in south-central Montana and northern Wyoming in 2003, and Malta in north-central Montana in 2003 was collected. Sage-grouse hens were fitted with radio collars and tracked to nests. Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young) canopy cover, density, and height for nest vs. random sites and brood vs. random sites were compared to determine if hens were selecting for these parameters. Forb, grass, total herbaceous, and residual cover, grass height, and residual height were also compared. Nest sites near Roundup (53 nest sites), Decker (58), and Malta (45) were measured. Most nest sites near Roundup were in sagebrush (91 %). All nest sites near Decker and Malta were in sagebrush. Only nest sites in sagebrush habitats were analyzed. Nest sites had taller (48 vs. 42 cm, P ¡Ü 0.01) and more productive (60 vs. 46 g of produced forage, P ¡Ü 0.01) nest shrubs than random sites near Roundup. At the Decker study area, nest sites had greater sagebrush cover (22 vs. 14 %, P ¡Ü 0.01), density (1.1 vs. 0.6 shrubs per m2, P ¡Ü 0.01), and taller shrubs within 15 m (52 vs. 42 cm, P ¡Ü 0.01) than random sites. Nest sites had taller shrubs within 15 m of the nest (30 vs. 26 cm, P ¡Ü 0.05) near Malta. Successful and failed nest sites did not differ between the Roundup and Decker study areas. Yearling nest sites had shorter grass than adult sites in Roundup (9 vs. 11 cm, P ¡Ü 0.05). Forty-four brood sites near Roundup and 73 brood sites near Decker were measured. Brood sites were not measured near Malta. Most brood sites near Roundup (71 %) and all near Decker (100 %) were in sagebrush. Only brood sites in sagebrush habitats were analyzed. Vegetation was similar between brood and paired random sites near Roundup. At the Decker study area, brood sites had denser sagebrush (1.1 vs. 0.6 shrubs per m2, P ¡Ü 0.01) than random sites. Adult and yearling hen brood sites did not differ near Roundup. Adult brood sites had greater sagebrush cover (14 vs. 8 %, P ¡Ü 0.05), density (1.0 vs. 0.6 shrubs per m2, P ¡Ü 0.05), and taller shrubs within 15 m (44 vs. 37 cm, P ¡Ü 0.05) than yearling sites near Decker. Brood sites had less shrub cover at 4 weeks than weeks 1 and 2 (10 vs. 16 and 17 %, P ¡Ü 0.01) near Roundup. Sagebrush habitats comprised 97 % (151 of 156) of the total nest sites and 92 % (108 of 117) of all brood locations. Nest sites had 19·C22 % sagebrush cover, 26·C52 cm sagebrush heights, and total herbaceous cover of 13·C33 %. Brood sites had 12-13 % sagebrush cover, 22·C43 sagebrush heights, and 14·C33 % total herbaceous cover. This study reinforces the importance of sagebrush habitats for nesting and brood-rearing sage-grouse. Management practices which remove this shrub would probably reduce the nesting and brood-rearing success of sage-grouse in central Montana and northern Wyoming.

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