Are sage-grouse fine-scale specialist or shrub-steppe generalist?

Authors: SMITH, J - University Of Montana; ALLRED, B - University Of Montana; Boyd, Chad; CARLSON, J - Bureau Of Land Management; Davies, Kirk; HAGEN, C - Oregon State University; NAUGLE, D - University Of Montana; OLSEN, A - Oregon State University; TACK, J - Us Fish And Wildlife Service

Submitted to: Journal of Wildlife Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2020
Publication Date: 4/29/2020
Publication URL: https://handle.nal.usda.gov/10113/7019792
Citation: Smith, J.T., Allred, B.W., Boyd, C.S., Carlson, J.C., Davies, K.W., Hagen, C.A., Naugle, D.E., Olsen, A.C., Tack, J.D. 2020. Are sage-grouse fine-scale specialist or shrub-steppe generalist? Journal of Wildlife Management. 84(4):759-774. https://doi.org/10.1002/jwmg.21837.
DOI: https://doi.org/10.1002/jwmg.21837

Interpretive Summary: Sage-grouse are species of conservation concern in the western United States. Management objectives for fine-scale vegetation characteristics such as height and cover of plant functional groups have been widely adopted based on relationships reported from field studies. There remains substantial disagreement, however, regarding which fine-scale vegetation characteristics matter, how much, and in what contexts and if they apply at the scale of management units. We employ meta-analyses to examine the role of vegetation structure in nest site selection and nest success across the geographic range of greater sage-grouse. None of the tested vegetation characteristics were related to variation in nest success, suggesting inappropriately extrapolated in developing range-wide habitat management objectives. Our findings cast doubt on the value of precise management objectives for fine-scale habitat structure.

Technical Abstract: Sage-grouse(Centrocercus spp.) are influencing rapidly evolving land management policy inthe western United States. Management objectives for fine-scale vegetation characteristics (e.g., grass height >18 cm) have been adopted by land management agencies based on resource selection or relationships with fitness proxies reported among numerous habitat studies. Some managers, however, have questioned the appropriateness of these objectives. Moreover, it remains untested whether habitat–fitness relationships documented at fine scales (i.e., among individual nests within a study area) also apply at scales of management units (e.g., pastures or grazing allotments), which are many orders of magnitude larger. We employed meta-analyses of studies published from 1991 to 2019 to help resolve the role of fine-scale vegetation structure in nest site selection and nest success across the geographic range of greater sage-grouse (C. urophasianus) and evaluate the validity of established habitat management objectives. Specifically, we incorporated effects of study design and functional responses to resource availability in meta-regression models linking vegetation structure to nest site selection, and used a novel meta-analytic approach to simultaneously model vegetation structure and its relationship to nest success. Our approach tested habitat relationships at a range-wide extent and a grain size closely matching scales at which agencies make management decisions. We found moderate, but context-dependent, effects of shrub characteristics and weak effects of herbaceous vegetation on nest site selection. None of the tested vegetation characteristics were related to variation in nest success, suggesting nesting habitat–fitness relationships have been inappropriately extrapolated in developing range-wide habitat management objectives. Our findings reveal surprising flexibility in habitat use for a species often depicted as having very particular fine-scale habitat requirements, and cast doubt on the practice of adopting precise management objectives for vegetation structure based on findings of individual small-scale field studies.