Recent Records of Birds from the Yampa Valley, Northwestern Colorado

Few areas within the western United States remain as superficially explored ornithologically as the northern basins of the plateau area of Colorado and Utah, west of the Continental Divide, a region isolated from population centers and universities by high mountain rims. Results of the 1937 Carnegie Museum Expedition include systematic description of the avifauna occupying certain habitats within Utah’ s Uinta Basin (Twomey 1942). No equally intensive effort has dealt with the status of birds between this basin and the Continental Divide to the east. The relatively few distributional records originating prior to the mid1960s for this region of Colorado have been included in Bailey and Niedrach’ s (1965) compendium of Colorado State birds, and field ornithologists’ identifications for all of western Colorado up to 1969’ have been assembled by Davis ( 1969). Commencing in November 1970 and continuing through July 1973, we have censused the composition and seasonal changes of the avian communities of two vicinities in the Yampa Valley of northwestern Colorado. One sampling locality centers at a proposed power plant site 12 km SW of Craig, Moffat County and includes the valley as far east as Craig itself. Elevations of censused communities range from 1860 to 2250 m. The other site is 38 km to the east in Routt county and centers at Hayden Station, a coal-fired, steam electric plant 6.4 km E of Hayden; it includes low, mountainous areas 8 km to the southeast. At the Hayden study site, elevations are from 198’ 0 to 2430 m. Habitats at the two vicinities are comparable. Vegetation included woodland communities along the Yampa River flood plain comprised of open stands of narrowleaf cottonwood ( Populus angustifolia) , box elder ( Acer negundo ), and river hawthorn ( Crutuegus rivuZuris) having an understory of scattered dense patches of red-osier dogwood (Cornus stoloniferu) and snowberry ( Symphoricurpos oreophilus); riparian hay pastures; croplands of alfalfa and wheat; northern desert shrub stands of big sagebrush (Artemisiu tridentuta) and rabbitbrush (Chrysothumnus nuuseosus); mountain shrub rangeland of serviceberry ( Amelunchier alnifolia ) , choke cherry ( Prunus uirginiuna ) , mountain mahogany ( Ce~cocu~pus montanus), snowberry, and Gambel’ s oak (Quercus gumb&i); and cattail marsh, pond, and stream habitats. Southeast of Hayden at Grassy Creek, graded coalmine spoil banks in various early stages of revegetation were also censused, as were nearby small stands of aspen (Populus tremuloides) and Douglas fir ( Pseudotsugu menziesii) found on north-facing slopes up to 2436 m elevation. Montane or subalpine forests were not included in the study areas. One hundred seventy-five species were encountered during 19 field periods including all months of the year except January; however, in this report we deal