Patterns of nest survival, movement and habitat use of sagebrush-obligate birds in an energy development landscape
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The sagebrush ecosystem in western North America provides habitat for approximately 350 plant and animal species, many of which are species of conservation concern. The sage-grouse and several species of sagebrush associated songbirds have undergone population declines over the last fifty years. Energy development has been identified as one of the leading causes of sagebrush landcover loss and fragmentation and has contributed to declines of sagebrush dependent bird species. Our research represented management-oriented science related to the conservation of sagebrush associated species. We used a sagebrush-obligate songbird, the Brewer’s sparrow (Spizella breweri breweri), and the greater sage-grouse (Centrocercus urophasianus, hereafter sage-grouse) to address questions related to habitat selection, space use, reproductive rates and movements in an established energy field in the Powder River Basin (PRB) in Wyoming, USA. Attaching global positioning system (GPS) tags to wildlife can provide a tremendous amount of information that can be used to better understand many aspects of a species’ ecology and how wildlife may be responding to anthropogenic disturbances. Information gathered from tracking wildlife is critical to inform management and conservation actions designed to benefit species that are being effected by anthropogenic activities. To minimize impacts and increase capturing efficiency when capturing sage-grouse to attach GPS tags, we developed a new mobile capturing technique. We had a 71% capture success rate. The capturing method we describe proved effective in our study and we believe this method can be applied to other bird species with similar behavioral traits. For most wildlife species, researchers must select between multiple tracking technologies that represent trade-offs among data requirements, mass, and cost. Options tend to be more limited for smaller species and those that fly. To address our research question, we developed and tested a unique combination of a store-on-board GPS logger with an independent very-high-frequency (VHF) tag (hereafter hybrid tag) fitted on sage-grouse with a modified harness design. We compared the hybrid tag we designed with other tracking technologies commonly used in bird research, namely VHF and Argos satellite relay tags. Given our research objectives, that required both frequent location data and field-based observational data, we found hybrid tags were the most cost-effective option and capable of collecting more location data compared with Argos tags because of power savings associated with data transmission. Cost savings allowed us to avoid sacrificing sample size while still obtaining high-resolution location data in addition to field-based observational data such as the presence of sage-grouse chicks. We believe our hybrid tags and harness design would be beneficial to research on other bird species of comparable size to sage-grouse and those that are relatively localized year-round, including many other Galliformes. Habitat selection in wildlife occurs across multiples spatial scales from selection for broad geographic areas to fine-scale habitat components. Therefore, the selection scale of interest in a study must dictate the spatial extent of the area considered as available to the species and availability should be based on biologically realistic movements of that species or individual. Habitat selection studies are usually conducted at a population level. Habitat selection analyses at an individual level can reveal patterns in selection that are not apparent when using population-level approaches. The hybrid tag, that allowed for gathering high-resolution location and movement data, and new data analyses approaches allowed us to explore individual-level movements, space use (e.g., home ranges) and habitat selection of female sage-grouse that raised chicks (brood-rearing sage-grouse) in a coal-bed natural gas (CBNG) development area. We used integrated step selection analysis (iSSA) that permit the quantification of the effects of environmental and anthropogenic covariates on the movement and selection process simultaneously to evaluate habitat selection and avoidance behaviors. On average, brood-rearing female sage-grouse established home ranges in areas with a majority of the home range comprised of sagebrush landcover (mean = 77.4%) and a minimal proportion of the area comprised of anthropogenic surface disturbance (mean = 3.5%). Individual-level selection analyses helped us uncouple some aspects of energy development that influence habitat selection that likely would not have been detected at broader spatial scales. Brood-rearing females consistently selected for natural vegetation and avoided disturbed surfaces, including reclamation surfaces, at fine spatial scales. Power line visibility generally led to avoidance behavior; however, much shorter (3m) CBNG well structures generally did not. We found that individual variability was partially explained by age (adult or first year), or previous experience of the landscape. Our results do not support individual uniformity in brood-rearing sage-grouse and reiterate the importance of accounting for, or at least recognizing, individual variability in population-level modeling efforts. Reclamation is increasingly emphasized as a means of mitigating impacts on species that have been affected by oil and gas development; however, the response of sagebrush species to reclamation has largely been untested. We used the Brewer’s sparrow nest survival as an indicator of population fitness responses to early-stage reclamation in sagebrush habitat. Addressing the question: does early-stage reclamation of energy disturbance provide a population benefit for the Brewer’s sparrow? We assessed oil and gas reclamation approximately five years after reclamation, but sagebrush reestablishment is a slow process; thus, the legacy of these disturbances (i.e., disturbance scars) will likely remain for decades. We compared Brewer’s sparrow nest survival across a gradient of oil and gas development from undisturbed and active development to areas that have undergone oil and gas reclamation. Nest survival was assessed at multiple scales from microhabitat to landscape. Our study was designed to also help us better understand the mechanisms that act to depress songbird nest survival in oil and gas development fields (i.e., physical footprint of disturbance or infrastructure features). The distribution of nest sites in the active CBNG development and reclamation treatments suggested local avoidance of disturbance, both active disturbance and reclamation, when establishing nesting territories. We found that reclamation benefited nest survival at a local scale which suggests that infrastructure, and associated human activity, may be more influential on Brewer’s sparrow nest predation risk than the physical footprint of disturbance alone. Our findings demonstrated scale-dependent nest survival relationships. Across microhabitat and landscape scales, sagebrush canopy cover and composition are important to Brewer’s sparrow reproductive success. Combined, these findings emphasize the importance of avoiding the removal of sagebrush habitat whenever possible and expediting sagebrush regeneration in disturbed areas to maintain suitable sagebrush habitat for breeding songbird populations.
Cite this version of the work
Christopher Kirol (2021). Patterns of nest survival, movement and habitat use of sagebrush-obligate birds in an energy development landscape. UWSpace. http://hdl.handle.net/10012/16844