Anthropogenic effects on avian populations in a high elevation fen wetland

Background/Question/Methods Cucumber Gulch Preserve, a fen wetland complex, is located at an elevation of 3000 meters near the town of Breckenridge, Colorado. Due to its value to wildlife it has been designated an Aquatic Resource of National Importance (ARNI) by the EPA. Recent anthropogenic alterations such as gondola construction and lodge development occurred in 2006 and resulted in approximately two linear kilometers of deforestation or an equivalent loss of five percent total forest. An increase in recreational activity and continual development along the perimeter of the wetland are a constant form of disturbance. In order to determine the potential effects on avian species, point-count surveys were conducted at 14 randomly chosen locations from May to August 2004-2008. We predicted that the anthropogenic activity in the form of deforestation and continual development along the edge of the preserve would have an unrecoverable impact on avian populations. Species that are positively associated with human disturbance will increase, whereas species that are particularly sensitive to disturbance will decrease. Results/Conclusions Our results indicate a significant increase in the abundance of avian species positively associated with anthropogenic disturbance (r²=0.76, p=0.05; American Crow, American Robin, and Brown-headed Cowbird). This positive trend is in contrast to state-wide data from the Rocky Mountain Bird Observatory which demonstrated no overall change in abundance of these species (r²=0.37, p=0.28). Surprisingly, there was a 500% increase in the number of Brown-headed Cowbirds. Those species that have been identified as sensitive species showed variable results: Violet-green Swallows, Brown Creepers, and Warbling Vireos showed an immediate negative response to deforestation activities (t=2.78, p=0.02). However, the Violet-green Swallows and Brown Creepers appeared to recover afterwards. The dramatic decrease in Warbling Vireos was also consistent with state-wide trends. Overall, anthropogenic activity in close proximity to critical habitat profoundly effect avian communities. Our study suggests that the impact is differential on populations and studies of avian communities should also conduct analyses at the species level to fully understand which species benefit and which are most harmed by human disturbance.