Bird and mammal response to large-scale habitat mitigation for game species in the oil and gas fields of Northwest Colorado

My dissertation is organized as follows. In Chapter 1, I synthesize the global scientific literature on the effects of habitat manipulation intended to enhance habitat for game species on non-target wildlife; in Chapters 2 and 3, I assess the long-term effects of pinyon-juniper removal on bird and mammal communities, respectively; and in Chapter 4, I compare and contrast the effects of mechanical and natural disturbance on bird and mammals in pinyon-juniper woodland.;To quantify and compare studies that measured the effects of game management on non-targeted animals, I surveyed the global literature and addressed the following research questions: 1) How many studies have investigated the effects of game management strategies on non-target species?, 2) What proportion of these studies document positive, negative or no effect of game management activities on non-target taxa?, and 3) What are the mechanisms underlying these effects? I found surprisingly few studies (n = 26) that evaluated the consequences of game management on other taxa. The outcomes of these studies illustrated that, through diverse mechanisms, game management can have either a positive, negative or no effect on non-target taxa. My analysis suggests that the explicit evaluation of the effects of game management on other species is rare but warranted, offering opportunities to advance ecological understanding and conservation of both target and non-target species. I propose a research agenda to fill knowledge gaps and catalyze a conversation about an approach to wildlife management that affects a large fraction of public and private land.;To partially address this research gap, I investigated whether tree removal to enhance habitat for mule deer and increase forage for livestock has altered bird and mammal communities in pinyon-juniper woodlands mechanically disturbed over 40 years ago, relative to sites that had not been mechanically disturbed (reference woodlands). Whether, and how, natural communities recover after human-induced habitat disturbance are critical questions facing ecologists and conservation practitioners. Forested ecosystems in the western U.S. have been the focus of tree reduction efforts for decades, with the intent of improving forage for livestock and economically important wildlife. Yet, the long-term consequences of tree removal on biodiversity are virtually unknown. To assess whether bird communities differ between historically disturbed and reference woodlands, and to determine if these differences are associated with particular habitat characteristics, I conducted bird and vegetation surveys where trees were mechanically removed by chaining over forty years ago and woodlands that had not experienced large-scale disturbance. I evaluated differences in avian species richness, diversity, community evenness, and used a Bayesian hierarchical approach to compare density between historically disturbed sites and reference sites. I found that tree reduction catalyzes a long-term change from dense pinyon-juniper woodlands to sagebrush scrub, fundamentally altering bird community composition. Disturbed sites were used by fewer species (J-evenness was 0.75 and 0.83 for disturbed and reference sites respectively) and largely dominated by shrubland-obligate birds---e.g., Green-tailed Towhee (Pipilo chlorurus); whereas, the most common birds in reference sites were woodland birds---e.g., Mountain Chickadee (Poecile gambeli). Further, bird densities were markedly different between disturbed sites and reference sites. Densities of many species were influenced by specific vegetative characteristics, such as mean tree diameter, that could be factored into management decisions.;I assessed whether mammal habitat use differed between reference pinyon-juniper woodlands and stands that were mechanically disturbed by chaining more than 40 years ago using remotely triggered wildlife cameras in historically chained sites (n = 22) and reference sites (n = 22). My results demonstrate marked differences in habitat use between chained sites and reference sites for most detected mammal species. Bobcat, mountain lion, American black bear, golden-mantled ground squirrel, and rock squirrel all showed a negative response to historically chained sites, indicating long-term effects of tree removal on these species. In contrast, habitat use of chipmunk, mountain cottontail, and coyote did not differ between chained and reference sites. Similar to birds, mammal habitat use of most species was influenced by specific vegetative characteristics, such as proportion of tree cover, which could be factored into management decisions.;Finally, I evaluated the ecological consequences of simulating natural disturbance as habitat mitigation for game species in a landscape undergoing energy development. Specifically, I investigated whether birds and mammals responded differently to mechanical tree reduction and natural disturbance (wildfire) in the Piceance Basin. My research objectives were to evaluate the differences in bird and mammal community composition, bird densities, and mammal habitat use immediately following mechanical tree removal and wildfires. I found little difference in species composition between mechanically disturbed sites and wildfire sites. However, I found marked differences in bird densities and mammal habitat use between mechanically disturbed woodlands and woodlands that were subject to wildfires. (Abstract shortened by UMI.).