This very extensive ecoregion includes two disjunct areas. Ecoregions adjacent to the northern part (of WA and northern OR) include the following: i) to the east is the Eastern Cascades Forests (NA0512); ii) to the northeast there is a small overlap with the Cascade Mountains Leeward Forests (NA0507); iii) almost all of the the rest of this part of the ecoregion (to the north, west, and south) is the Palouse Grasslands (NA0813); and iv) the two southern fingers of this ecoregion area touch against the Blue Mountains Forests (NA0505) (this ecoregion fills the small gap to the main area of the ecoregion). The main area of the ecoregion is bordered: to the northwest by the afore-mentioned NA0505; v) to the northeast and east by the South Central Rockies Forests (NA0528); to the south by the Great Basin Shrub Steppe (NA1305); vi) in the extreme southwest by the Sierra Nevada Forests (NA0527); and to the west, again by the Eastern Cascades Forests.
The northern teardrop covers the steppe area of Washington and northern Oregon that abuts the Cascade Range to the west and the Blue Mountains to the south (essentially the western portion of the Columbia Basin). To the north and west it transitions to the Palouse Grasslands.
The southern part occupies the entire southeastern quarter of Oregon, a tiny part of California northeast of the Sierra Nevada Range, the northern fringe of Nevada, and southern Idaho south of the Bitterroot Range. It also includes an insignificant sliver of Wyoming east of Grand Teton National Park. It follows the trajectory of the Snake River and then the Deschutes River, down to the Columbia Basin — thus the name of the ecoregion.
Description of the Ecoregion
The ecoregion was described in the WWF publication “Terrestrial ecoregions of North America” (Ricketts, et al., 1999); essentially the same text can be found on-line at WWF’s site: www.worldwildlife.org. The map above is a screen shot from WWF’s Wildfinder site, now offline. There may also be additional information to be found on this ecoregion’s page at Wikipedia or at other sites.
At least in Washington, the extent of this ecoregion is for the most part the same as the EPA’s “Columbia Plateau Ecoregion”, as mapped at Bird Web of the Seattle Audubon Society (SAS). WWF separates out however the exterior band to the north and west which they place in the Palouse Grasslands.
Briefly, the ecoregion is characterized by WWF as a mostly arid ecoregion dominated by sagebrush (Artemisia spp.) and various grass species. Included mountainous areas grade into bunchgrass and juniper woodlands (with some areas of Douglas fir, subalpine fir, and aspen. In general, this ecoregion is not as hot and dry as the Great Basin Shrub Steppe to the south. Riparian areas contain cottonwoods and willows. Southeastern Oregon additionally includes the Malheur NWR, a very large wetland area.
Birds of the Ecoregion
No general information has been found describing the birds of the ecoregion. My own analysis is pending. It will presumably be very similar to that of the Great Basin Shrub Steppe to the south, skewing toward species that are more hardy and less tolerant of very arid conditions. In the areas with isolated mountains, one would expect clusters of species typical of nearby montane coniferous ecoregions.
The large wetland complex of Malheur NWR is noteworthy as being one of the most important waterfowl stop-over sites of the Pacific Flyway with seasonally huge numbers of geese, ducks, and other species.
Resources for the Ecoregion Birder
Without any pretence to completeness, the following resources have caught my attention and would be of value to the birder traveling to this ecoregion:
- Seattle Aubudon Society’s Bird Web is a terrific resource for Washington state (note that their Columbia Plateau ecoregion is partially split off by WWF into the Palouse Grasslands so their lists should be interpreted with care).
DJG: 80 spp. (August 16, 2019)