| Ecological sites are used as a foundation for land managers to identify soil, hydrologic, and plant community characteristics, but have not yet been used to address wildlife habitat. Quantifiable links are needed between ecological site characteristics and wildlife habitat. Site characteristics and songbird density and diversity were quantified on four shrub-steppe ecological sites at Browns Park National Wildlife Refuge in northwestern Colorado. Our objectives were to (1) quantify ecological site characteristics using common and modified monitoring methods, (2) relate ecological site characteristics to songbird metrics, and (3) develop and validate a vegetation structure metric. Ecological sites differ in species composition, height, canopy gaps, and shrub density. Modified gap intercept and shrub belt transect methods illustrated vegetation structure more effectively than line-point intercept. Brewer's sparrows (Amphispiza belli) were associated with plant height, basal gaps, and shrub density. Sage sparrows (Spizella breweri) were associated with sagebrush-dominated sites, but were also influenced by squirreltail and plant gaps. Songbird diversity was greater in mixed, short plant communities within and among sites. A vegetation structure (VS) metric was developed using shrub height, plant canopy gap, and low shrub density fraction. VS differentiated ecological sites and songbird habitats at Browns Park. This research links ecological sites with wildlife habitat and presents monitoring tools to evaluate shrub steppe conditions and determine potential of ecological sites to support desired habitat. |
