Habitats and their associated birds Colorado is blessed with a tremendous variety of habitat types, which results in a tremendous variety of birds. In order to find a bird, you are best off looking for its habitat, and this requires at least a basic knowledge of Colorado's flora and geology. This section describes the main habitat types and some birds that are associated with them and may be hard to find elsewhere. Sagebrush Foothill Shrubs Spruce-Fir Forest Yucca Ponderosa Pine Forest Alpine Tundra Shortgrass Prairie Aspen Groves Cliff Faces Lowland Riparian Woodland Lodgepole Pine Forest Subalpine Life Zone Scrub Oak Woodland Streamside Willows Rimrock and Mesa Country Pinyon-Juniper Forest Quaking Aspen (Populus tremuloides) is one of Colorado's most unmistakeable trees, especially considering that white birches do not occur in the state. Scattered individual aspens may grow in the ponderosa and lodgpole belts, or entire hillsides may be covered by pure stands, some of which may be the result of the vegetative spread of a single individual! Many species rely on cavities in aspens for nesting purposes, and therefore the birding tends to be best in the most mature groves--the ones where the trees have the largest diameter. Look here for sapsuckers, small owls, Empidonax flycatchers and Warbling Vireo.