Fig 1.
A map of the area where we studied cliff organisms west of Boulder, Colorado, USA, in 2015.
Cliff formations used in the study are indicated by circles (black = low-use climbing sites, white = high-use climbing sites). Hiking trails are drawn in bright green. Basemap was created using ArcGIS software by Esri [25]. ArcGIS and ArcMap are the intellectual property of Esri and are used herein under license. Copyright Esri. All rights reserved. For more information about Esri software, please visit www.esri.com. Trails were obtained from the City of Boulder GIS portal [26].
Table 1.
Values of cliff attributes for study sites.
Data are presented as averages ± standard error of the mean, n = 16 for each cliff category.
Fig 2.
The surveyed area is indicated in light gray and included a 30 m wide section of cliff (height varied with site), a triangular space stretching to the researcher positioned 20 m away from the cliff base, and the air space above the cliff and triangular space. Dashed lines indicate vertical vegetation transects, squares indicate 0.25 m2 vegetation plots, triangles indicate arthropod traps.
Table 2.
Numbers of high- and low-use climbing sites at which avian species were observed.
Bold font indicates species which have previously been documented nesting in cliff habitats of Boulder Open Space and Mountain Parks [15].
Fig 3.
Comparison of (A) avian diversity (B) avian species richness (C) number of individual birds present between high and low use climbing areas. Numbers are based on overall survey averages for high and low-use climbing site surveys (n = 91each for the high and low categories) ± SEM. Individuals were summed across species. “Survey Area” refers to birds observed within the total survey area, “Cliff” indicates birds that were observed on the rock formation itself.
Fig 4.
Community conservation value (CCV) by cliff aspect and climbing use rating.
Numbers are based on overall survey averages for high and low-use climbing site surveys (n = 91 each for the high and low categories) ± SEM. Individuals were summed across species.
Table 3.
Summary of models from LMMs for avian diversity, avian species richness, bird abundance, community conservation value, and cliff use where ΔAICc is within 2 of the best fit model.
The best model for each response variable is listed first. See appendix for complete summaries of all evaluated models.
Table 4.
Summary of vegetation data (mean ± standard error) at high versus low use climbing sites.
Table 5.
Comparison of arthropod order counts and presence at high- versus low-use climbing sites.
Numbers indicate at how many sites each order was observed. n = 10 sites of each type with 44 traps at high-use climbing sites and 47 traps at low-use climbing sites.