Anthropogenic and natural disturbance differentially affect sagebrush bird habitat use

Authors: DUCHARDT, COURTNEY - University Of Wyoming; Augustine, David; BECK, JEFF - University Of Wyoming

Submitted to: Journal of Wildlife Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2020
Publication Date: 6/17/2020
Publication URL: https://handle.nal.usda.gov/10113/7019844
Citation: Duchardt, C., Augustine, D.J., Beck, J. 2020. Anthropogenic and natural disturbance differentially affect sagebrush bird habitat use. Journal of Wildlife Management. 84(7):1361-1372. https://doi.org/10.1002/jwmg.21907.
DOI: https://doi.org/10.1002/jwmg.21907

Interpretive Summary: Populations of many bird species associated with sagebrush rangelands in North America are declining, often due in part to human development of these lands. At the eastern edge of where sagebrush occurs, habitat for these birds may also be negatively affected by a native herbivore, the black-tailed prairie dog, because they girdle and kill sagebrush. We examined the degree to which variation in the abundance of three species of sagebrush-associated birds was related to vegetation, human development (mines, roads, oil and gas wells), and locations of black-tailed prairie dog colonies using data collected for the Thunder Basin National Grassland in eastern Wyoming. For the greater sage grouse, we analyzed abundance using long-term records of lek surveys. For the other two species, Brewer's sparrows and sage thrashers, we analyzed abundance based on point-count surveys. Comparisons of different models of variation in bird abundance consistently showed that models based on human development (distance to mine, well density, and road density) outcompeted models based on prairie dog colony locations. However, after accounting for the influence of human development, long-term presence of prairie dog colonies in a locality did negatively influence abundance of sagebrush-associated birds. However, becasue prairie dogs are periodically decimated by disease outbreaks in this landscape, their long-term effects on bird habitat are limited in extent. Conversely, human development is slated to increase in this landscape, suggesting potentially accelerated declines for sagebrush-associated birds into the future.

Technical Abstract: North American sagebrush-obligate (Artemisia spp.) birds are experiencing steep population declines due in part to increased disturbance, mainly human-caused, across their range. At the eastern edge of the sagebrush steppe, this issue may potentially be exacerbated due to natural disturbance by ecosystem engineers including the black-tailed prairie dog (Cynomys ludovicianus). Our goal was to compare local and landscape models of habitat use by greater sage-grouse (Centrocercus urophasianus), Brewer’s sparrow (Spizella breweri), and sage thrasher (Oreoscoptes montanus) with models including effects of both natural (i.e., prairie dog) and anthropogenic disturbance. We used a combination of field data collection, and state and national datasets for the Thunder Basin National Grassland of eastern Wyoming to determine which factors drive lek attendance by sage-grouse and habitat use by two passerines in this system. For all three species, models including big sagebrush cover at both local and landscape scales were the most competitive among univariate models, supporting the paradigm that sagebrush is key for these species. Overwhelmingly models including anthropogenic disturbance (well density, road density) outcompeted models of prairie dog disturbance alone, although long-term disturbance by prairie dogs did reduce abundance of sagebrush-obligate songbirds. While long-term prairie dog disturbance has the potential to reduce habitat quality for sagebrush-obligate birds, such events are likely rare due to outbreaks of plague (Yersina pestis) and lethal control on borders with private land. Conversely, anthropogenic disturbance is slated to increase in this system, suggesting potentially accelerated declines for sagebrush birds into the future.