We agree with the assertion made in the Supplementary EA that “Common ravens and many other species have been documented to eat sage-grouse eggs.” However, the specific impact of common raven predation on sage-grouse nest success and survival of chicks is unclear as indicated by a modeling study in Nevada which showed that American badger were just as likely to depredate sage-grouse nests (Coates and Delehanty 2004). The available data do not suggest that removal of common ravens will increase counts of sage-grouse on leks. The recent paper by Robinson and Messmer (2013) indicated that sage-grouse survival rates, nest success, and brood success were greater in an area receiving less intense predator control and no raven control compared to an area with more overall predator control and raven removal. Dinkins’ dissertation (2013) did not detect a significant increase in sage-grouse nesting success following a 61% reduction of a raven population by APHIS in Wyoming. Dinkins found that nesting success was positively correlated with the selection of rugged habitat. He did find that sage-grouse nesting success was 22% when ravens were detected within 550m of a sage-grouse nest, and 41% when no ravens were detected within 550m of a nest; however these relationships are correlative and do not show causation. Correlative relationships may exist because different species prefer different habitat.
Coates, P.S. and D.J. Delehanty. 2004. Nest Predation of Greater Sage-Grouse in Relation to Microhabitat Factors and Predators. J. Wildlife Management. DOI: 10.2193/2009-047
Connelly, J. W., S. T. Knick, M. A. Schroeder, and S. J. Stiver. 2004. Conservation Assessment of Greater Sage-grouse and Sagebrush Habitats. Western Association of Fish and Wildlife Agencies. Unpublished Report. Cheyenne, Wyoming.
Dinkins, J.B. 2013. Common raven density and greater sage-grouse nesting success in southern Wyoming: Potential conservation and management implications. PhD Dissertation. Utah State Univ.
Knick, S. T., and J. W. Connelly (editors). 2011. Greater Sage-Grouse: ecology and conservation of a landscape species and its habitats. Studies in Avian Biology Series (vol. 38), University of California Press, Berkeley, CA.
Manier, D.J., Wood, D.J.A., Bowen, Z.H., Donovan, R.M., Holloran, M.J., Juliusson, L.M., Mayne, K.S., Oyler-McCance, S.J., Quamen, F.R., Saher, D.J., and Titolo, A.J., 2013, Summary of science, activities, programs, and policies that influence the rangewide conservation of Greater Sage-Grouse (Centrocercus urophasianus): U.S. Geological Survey Open-File Report 2013–1098, 170 p., http://pubs.usgs.gov/of/2013/1098/.
Robinson, J.D. and T.A. Messmer. 2013. Vitals rates and seasonal movements of two isolated greater sage-grouse populations in Utah’s West Desert. Human-Wildlife Interactions 7(2):182–194, Fall 2013.
Heinrich, B. 1984. Ravens in winter. Vintage press.
Marzluff, J., and T. Angell. 2005. In the company of crows and ravens. Yale University Press.
Robinson, J.D. and T.A. Messmer. 2013. Vitals rates and seasonal movements of two isolated greater sage-grouse populations in Utah’s West Desert. Human–Wildlife Interactions 7:182–19.
USFWS. 2010. Endangered and Threatened Wildlife and Plants; 12-Month Findings for Petitions to List the Greater Sage-Grouse (Centrocercus urophasianus) as Threatened or Endangered. CFR Vol. 75, No. 55. March 23, 2010.
U.S. Fish and Wildlife Service. 2013. Greater Sage-grouse (Centrocercus urophasianus) Conservation Objectives: Final Report. U.S. Fish and Wildlife Service, Denver, CO. February 2013.