Landscape Collaborative Grazing and Greater Sage Grouse Survival

Objective 1: Expand capture design to include more birds.

In 2014, 51 females were captured from 5 leks and radio collared.  These birds dispersed to 50,000 acres.  In 2015, 58 sage-grouse hens were captured from 8 leks and they dispersed to 97,581 acres. In 2016, 55 sage-grouse hens were captured from 8 leks and they dispersed to 144,926 acres.

Objective 2: Estimate cattle grazing influences on sage-grouse nesting.

Cattle grazing in our study area of the Centennial Valley generally does not occur until most of the sage-grouse have completed nesting. In 2014 and 2015 our study focused on direct effects of cattle grazing. We only had two nests that experienced grazing effects by cattle (Table 1).

Table 1: Nests in pastures with and without cattle in 2014 and 2015

In addition to looking at direct effects of cattle presence on nest site selection, we also looked at indirect effects resulting from cattle grazing infrastructure (roads, fence lines, water tanks) and presence (cattle trails and density) over summers 2014-16 (Table 2). Distance to the nearest cattle path had a moderate effect on selection of nest sites for sage-grouse. Extended use by cattle in a given area, such as concentrated point sources (e.g. water tanks), may increase the number and linear distances of cattle paths in a given area. This in turn may increase sage-grouse nesting use of these areas. We suspect sage-grouse utilize these paths as travel corridors to and from their nests, and to aid in ease of movement throughout dense stands of sagebrush.

Table 2: Nest site selection in relation to cattle grazing infrastructure in 2014, 2015, and 2016.

Distance to fence line influenced nest survival (Table 3). On average, successful nests were 258 m further from fence lines than unsuccessful nests. Avian predators oftentimes use fence posts as perches, which could explain this difference. No other difference existed in terms of its mean grazing infrastructure influence on nest survival.

Table 3: Apparent nest survival in relation to cattle grazing infrastructure in 2014, 2015 and 2016.

Sage-grouse selected nest sites with more heat, including areas with more southerly aspects and steeper slopes (Table 4). Sage-grouse also selected habitats for nesting lower in elevation than available.

Table 4: Nest site selection in relation to abiotic factors, 2014, 2015 and 2016.

Elevation positively influenced nest survival (Table 5). Nests that hatched at least one young were found 55 m higher in elevation than unsuccessful nests. Our study area ranged in elevations from 2042 meters (6700 feet) to 2600 meters (8528 feet). 

Table 5: Apparent nest survival in relation to elevation and heatloading.

Sage-grouse selected nest sites with more dead grass, on average total height was 70 cm greater at nest sites than random sites (Table 6). For grass cover, forb cover, and species richness, sage-grouse selected nest sites with average values less than at random sites. These values could be driven by the large portion of female sage-grouse that nested in the big basin sagebrush habitat that has much lower grass, forb, and species richness than other sagebrush types.

Table 6: Nest site selection in relation to biotic (vegetative) indices.

 Of all the nest sites selected, successful nests seemed to be positively influenced by less dead grass height, greater forb cover, and greater species richness (Table 7). On average, successful nests had a total dead grass of 70 cm less than unsuccessful nest sites, forb cover was 8% greater, and number of total species found at nest sites was 21 versus 18 at unsuccessful nest sites.

Table 7: Apparent nest survival in relation to certain vegetative indices.

Objective 3: Estimate influence of habitat type on nesting success

At the end of the 2016 season, sage-grouse used 3,468 acres of low sagebrush, 7,587 acres of basin big sagebrush, 27,337 acres of three-tip sagebrush, and 69,795 acres of mountain big sagebrush.

Nesting success averaged 34% across all habitat types (Table 8). Sage-grouse did not nest in low sagebrush. Nesting success is usually dependent on factors that reduce predation rates.  Mountain big sagebrush plants provide the most cover for nests which would reduce predation due to increased concealment of the nest.

Table 8:  Nesting success (%) of sage-grouse by habitat type in the Centennial Valley, MT, 2014-2016.

Objective 4: Estimate grazing influences on sage-grouse brood home range size

Grazing utilization levels averaged 4% in brood home ranges in 2014 and 2015. (Table 9). The maximum utilization level recorded in a brood’s home range was 14% (Table 9). Therefore, utilization levels were very low in brood home ranges. We did not measure utilization levels in brood home ranges in 2016.

Table 9: Grazing utilization levels in brood home ranges of broods in pastures with cattle across 2014 and 2015.

There was no year effect (P = 0.66) in brood home range size, and brood home range size did not differ between grazed and ungrazed pastures (Table 10, 11, 12). The sample size for broods in pastures with cattle (n = 7) was low (Table 10), but two broods traveled >1 km into a pasture with cattle where they remained for over 2 weeks. We did not measure brood home ranges in 2016.

Table 10: Broods in pastures with cattle and without in 2014 and 2015.

Table 11: Differences in overall brood home range size (acres) between years 2014 and 2015.

Table 12: Differences in overall brood home range size acres) between pastures grazed and ungrazed by cattle in 2014 and 2015.

There were no differences (P = 0.39) in grass heights between 2014 and 2015 (Table 13) in pastures with sage-grouse broods.  This suggests growing conditions in both years were similar and differences in sage-grouse nest and brood survival were not due to environmental factors, but we have not tested this hypothesis.

Table 13:  Average grass heights (cm) by year.

Grazing did not reduce (P = 0.18) average grass height in pastures with and without cattle for both years (Table 14).  This provides evidence that grazing levels in our original and expanded area did not alter grass height.  Since most studies have indicated increased grass height will increase sage-grouse survival, it is unlikely that grazing altered brood survival, but we have not analyzed this.

Table 14:  Influence of grazing on average grass height (cm) during brood-rearing of sage-grouse in the Centennial Valley, MT, 2014-2015.

Seventy eight percent (35/45) of sage-grouse hens with broods used mountain big sagebrush and three-tip sagebrush vegetation types (Table 15). Less than one percent were found in big basin sagebrush.

Table 15: Habitat types used by broods across three years of the study.

Objective 5: Estimate the effects of grazing infrastructure on brood survival (2014-2016)

Broods that survived to 30-days of age were located closer to roads and water tanks than failed broods (Table 16). Successful broods were 129 m closer to roads and 385 m closer to water tanks on average compared to failed broods (Table 16). Successful broods closer to roads and water tanks could increase their movements, increase sighting distance, and increase vigilance of predator activity nearby.   However, successful broods were located on average 1.1 mile from the nearest water tank, but it is difficult to provide a biological reason for this finding.   

Table 16: Average distances (m) to fences, roads, and water tanks of successful (survived to 30-days old) and failed broods (died prior to 30-days of age)

Conclusion:

Current grazing practices in the Centennial Valley appear to have minimal effects on sage-grouse reproduction and survival during the nesting and brood rearing seasons.  Average nesting success was 34% across the 3-year study.  Cattle and sage-grouse generally overlap mostly during the brood-rearing period. Cattle had little effect on vegetation during the nesting and brood rearing season.  Cattle utilize a small portion of the total sagebrush landscape, which minimizes the chances of conflict between cattle and sage-grouse. We did not detect an influence of cattle on brood home range size, though we acknowledge the sample size was small. The only grazing effect we detected was that unsuccessful nests were closer to fence lines than successful nests.  Residual grass height did not influence nest survival as successful nests had less dead grass heights than successful nests. Sagebrush type and elevation appeared to have a stronger influence than livestock grazing on sage-grouse nest survival. Broods that survived to 30-days of age were found closer to roads and water tanks.  This suggests that grazing infrastructure attributes such as roads and water tanks currently do not have a negative influence on sage-grouse broods for the Centennial Valley of Montana.

Milestones 

Milestones for 2014:

1. Recruited graduate students Kyle Cutting (Ph.D.) and Sean Schroff (M.S.).
2. Captured 51 sage-grouse hens from 5 leks.
3. Held 3 organizational meetings of Team, Montana Fish Wildlife & Parks, Bureau of Land Management and Natural Resource Conservation Service representatives.
4. Measured sagebrush cover and herbaceous cover before cattle are introduced.
5. Measured vegetation before and after grazing in areas of light, moderate and heavy use.
6. Measured sagebrush cover and herbaceous cover at the nest.
7. Hosted 2 field days on June 5, 2014 (30 participants) and September 11, 2014 (35 participants)
8. Submitted Annual Report.

Milestones for 2015:

1. Captured 58 sage-grouse hens
2. Marked location of hens with and without cattle grazing
3. Delineated habitat type use by hens and estimated nesting success
4. Estimated brood home range size with and without cattle
5. Estimated grazing effects on herbaceous vegetation and sage-grouse survival
6. Estimated effects of habitat type on brood survival
7. Meeting to discuss sagebrush habitat grazing management with US Forest Service, US Fish and Wildlife Service, Montana Fish, Wildlife & Parks, Greater Yellowstone Coalition, and cattle and sheep producers. August 6, 2015, Dillon, MT.
8. Presented preliminary findings to scientists (Greater sage-grouse Grazing Research Meeting, hosted by Montana Fish, Wildlife & Parks and attended by researchers from Montana State University, Idaho Fish and Game, Idaho State University and Utah State University; November 4-5, 2015, Helena, MT.)
9. YouTube video of project completed December 2015, Link sent to WSARE for approval. (https://www.youtube.com/watch?v=AVGeIBjHnqY)
10. Submitted Annual Report.

Milestones for 2016:

1. Captured and marked 55 sage-grouse hens with radio-transmitters
2. Brought several ranchers together to discuss study findings, Lima, Montana
3. Met individually with U.S. Forest Service and Bureau of Land Management regarding grazing implications, Dillon, Montana.
4. Provided grazing recommendations to Montana Department of Natural Resource Conservation.
5. Presented study findings to The Nature Conservancy, Montana Fish, Wildlife, and Parks, and Department of Natural Resource Conservation Service, Helena, Montana.
6. Centennial Valley Association is promoting study results to ranching community.
7. Results provide recommendation for grazing management in the Centennial Valley.
8. Results presented to the Intermountain Section of the Society of Range Management, Nov 4, 2016. Bozeman, MT.
9. Results support sustainable grazing practices in high-elevation sagebrush sites.
10. Meeting with USFS, BLM, NRCS, USF&WS, and local land owners to present findings from this report. On Dec 12 and 21, 2016 in Lima and Helena, MT.
11. Submitted Annual Report.