Effects of Gunnison Sage-Grouse habitat treatment efforts on associated avifauna and vegetation structure

Conservation efforts over the last 20 years for the Gunnison Sage-Grouse (Centrocercus minimus) have involved extensive habitat manipulations done predominantly to improve brood rearing habitat for the grouse. However, the effects of Gunnison Sage-Grouse habitat treatments on sympatric avifauna and responses of vegetation to manipulations are rarely measured, and if they are, it is immediately following treatment implementation. This study examined the concept of umbrella species management by retrospectively comparing density and occupancy of eight sagebrush associated songbird species and six measures of vegetation in treated and control sites. Our results suggested that songbird densities and occupancy changed for birds at the extreme ends of their association with sagebrush and varied with fine-scale habitat structure. We found Brewer’s Sparrows (Spizella breweri) decreased in density on treated sites and Vesper Sparrows (Pooecetes gramineus) increased. Occupancy estimation revealed that Brewer’s Sparrows and Green-tailed Towhees (Pipilo chlorurus) occupied significantly fewer treated points whereas Vesper Sparrows occupied significantly more. Vegetation comparisons between treated and control areas found shrub cover to be 26% lower in treated sites. Lower shrub cover in treated areas may explain the differences in occupancy and densities of the species sampled based on known habitat needs. The fine-scale analysis showed a negative relationship to forb height and cover for the Sage Sparrow (Amphispiza belli) indicating, from vegetation measures showing grass and forb cover during a good precipitation year covered significantly more area in the treatment than the control sites, that Sage Sparrows may also not respond favorably to Gunnison Sage-Grouse habitat treatments. While the concept of an umbrella species is appealing, evidence from this study suggests that conservation efforts aimed at the Gunnison Sage-Grouse may not be particularly effective for conserving other sagebrush obligate species of concern. This is probably due to Gunnison Sage-Grouse habitat management being focused on the improvement of brood rearing habitat which reduces sagebrush cover and promotes development of understory forbs and grasses.

Evaluating the Potential Impact of a Gas Pipeline on Whimbrel Breeding Habitat in the Outer Mackenzie Delta, Northwest Territories

We used ground surveys to identify breeding habitat for Whimbrel (Numenius phaeopus) in the outer Mackenzie Delta, Northwest Territories, and to test the value of high-resolution IKONOS imagery for mapping additional breeding habitat in the Delta. During ground surveys, we found Whimbrel nests (n = 28) in extensive areas of wet-sedge low-centered polygon (LCP) habitat on two islands in the Delta (Taglu and Fish islands) in 2006 and 2007. Supervised classification using spectral analysis of IKONOS imagery successfully identified additional areas of wet-sedge habitat in the region. However, ground surveys to test this classification found that many areas of wet-sedge habitat had dense shrubs, no standing water, and/or lacked polygon structure and did not support breeding Whimbrel. Visual examination of the IKONOS imagery was necessary to determine which areas exhibited LCP structure. Much lower densities of nesting Whimbrel were also found in upland habitats near wetlands. We used habitat maps developed from a combination of methods, to perform scenario analyses to estimate the potential effects of the Mackenzie Gas Project on Whimbrel habitat. Assuming effective complete habitat loss within 20 m, 50 m, or 250 m of any infrastructure or pipeline, the currently proposed pipeline development would result in loss of 8%, 12%, or 30% of existing Whimbrel habitat. If subsidence were to occur, most Whimbrel habitat could become unsuitable. If the facility is developed, follow-up surveys will be required to test these models.