Spatially Explicit Modeling of Annual and Seasonal Habitat for Greater Sage-Grouse (Centrocercus urophasianus) in Nevada and Northeastern California - an Updated Decision-Support Tool for Management

Successful adaptive management hinges largely upon integrating new and improved sources of information as they become available. Updating management tools for greater sage-grouse ( Centrocercus urophasianus, hereafter referred to as sage-grouse) populations, which are indicators for the large-scale health of sagebrush ( Artemisia spp.) ecosystems in the Great Basin of North America, provide a timely example for this tenet. Recently developed spatially-explicit habitat maps derived from empirical data played a key role in the conservation of this species facing listing under the Endangered Species Act. Herein, this report provides an updated process for mapping relative habitat suitability and management categories for sage-grouse in Nevada and northeastern California (Coates and others, 2014, 2016). These updates included: 1) adding radio-and GPS telemetry locations from sage-grouse monitored at multiple sites during 2014 to the original location dataset beginning in 1998; 2) integrating output from high resolution maps (1 2 m 2) of sagebrush and pinyon-juniper cover as covariates in resource selection models; 3) explicit modeling of relative habitat suitability during three seasons (breeding, brood-rearing, over-wintering) critical to sage-grouse life history; 4) accounting for differences in habitat availability between more mesic sagebrush steppe communities in the northern part of the study area and drier Great Basin sagebrush in more southerly regions by categorizing continuous region-wide surfaces of habitat suitability index (HSI) with independent locations falling within two hydrological flood zones; 5) integrating the three seasonal maps into a composite map of annual relative habitat suitability; 6) deriving updated land management categories based on previously determined cut-points for intersections of habitat suitability and an updated index of sage-grouse abundance and space-use (AUI), and 7) masking urban footprints and major roadways out of the final map products.

Seasonal habitat maps were generated based on model-averaged resource selection functions derived for 10 project areas (813 grouse, 14,085 locations) during the breeding season, 10 during the brood-rearing season (591, 11,743), and 7 during the winter season (288, 4,862). RSF surfaces were transformed to HSIs and averaged in a GIS framework for each pixel for each season. Validation analyses of categorized HSI surfaces using a suite of independent datasets resulted in an agreement of 9397 percent for habitat versus non-habitat on an annual basis. Breeding and brood rearing maps validated similarly well at 94-97 percent, while winter maps validated slightly less accurately at 87-93 percent.

We provide an updated example of how space use models can be integrated with habitat models to help inform conservation planning. Using data, we combined probabilistic breeding density with a non-linear probability of occurrence relative to distance to nearest lek (traditional breeding ground) using count data to calculate the AUI. The AUI was then classified into two categories of use (high and low-to-no) and intersected with the HSI categories to create potential management prioritization scenarios based on information about sage-grouse occupancy coupled with habitat suitability. Compared to Coates et al (2014, 2016), the amount of area classified as habitat across the region increased by 6 percent (approximately 1,600,000 acres). For management categories, core increased by 7% (approximately 780,000 acres), priority increased by 7% (approximately 610,000 acres), and general increased by 12% (approximately 960,000 acres), while non-habitat decreased (that is, classified non-habitat occurring outside of areas of concentrated use) by 12 percent (approximately 2,400,000 acres). Importantly, seasonal and annual maps represent habitat for all age and sex classes of sage-grouse (that is; sample sizes of marked grouse were insufficient to only construct models for reproductive females). This revised sage-grouse habitat mapping product helps improve adaptive application of conservation planning tools based on intersections of spatially-explicit habitat suitability, abundance, and space use indices.