Put simply, southwestern Washington is the Westside’s Columbia Basin. Although its northwest and northeast corners are drained by the Chehalis and Nisqually Rivers, all the rest is in the Columbia River watershed. Culturally and economically, this region looks more to Portland/Vancouver than to the Puget Sound megalopolis—especially south of Centralia and Chehalis. Good birds are often reported to the Portland Rare Bird Alert (RBA) and the OBOL email list before they show up on Tweeters.

The Southwest was one of the first parts of Washington to be explored and settled by Euro-Americans. Lewis and Clark found few bird species new to science on their 4,100-mile Voyage of Discovery (1804–1806), and none in what is now Washington, even though they obtained several first state records. Fort Vancouver (which you can visit in Vancouver) played a prominent role in the area’s early ornithological history. While based here between 1834 and 1836, John Kirk Townsend identified eight new bird species and several other distinct forms, including Vaux’s Swift, Chestnut-backed Chickadee, Bushtit, Western Bluebird, MacGillivray’s, Audubon’s Yellow-rumped, Black-throated Gray, Townsend’s, and Hermit Warblers, and Oregon Dark-eyed Junco. John James Audubon depicted all of these, from Townsend’s specimens, in hisBirds of America. No California Condor is better known than the one that served for Audubon’s plate, a specimen taken by Townsend near the mouth of the Columbia.

The Southwest is differentiated into five subareas by its topography. On the west are the Willapa Hills, a low coastal range with few summits above 2,500 feet. On the east is the Cascade Range, rugged and remote, topped by Mount Adams at 12,276 feet. Another massive volcano, Mount Saint Helens, sits many miles west of the crest. Interstate 5 runs north and south down the middle of the third subarea—the lowlands between the coastal hills and the Cascades. The fourth subarea is the Columbia River bottomlands, especially those around Vancouver, and the last is the Columbia Gorge east to the Cascade divide.

The Willapa Hills are seldom visited by birders. Abundant rainfall blessed these hills with magnificent forests, but only scattered fragments of old growth have escaped the loggers. Nearly all of these lands belong to timber companies (with a few state forests) and are managed as tree farms, which limits bird species diversity. Gray Jay and Hermit Warbler are among the more interesting species to be found here if one takes the time to explore the hundreds of miles of logging roads.

The central lowlands—unglaciated, in contrast to glacially overriden Puget Sound to the north—consist of level ground or low hills, with few lakes. Much of this area was originally covered with Douglas-fir forests, but the deep alluvial soils prompted early clearing for agricultural use. In the northern part, from Chehalis south to Toledo, prairies and stands of Garry Oak still occupy patches of sandy, gravelly soils deposited by outwash from the melting glaciers farther north. Farther south, the Cowlitz River flows down to Longview, and the Columbia flows up to meet it, through a relatively narrow trough. Miles of tree farms extend to the east and west.

The plains around Vancouver are a northward continuation of Oregon’s Willamette Valley. As the last ice age came to a close (15,000–13,000 Before Present), each release from the failed ice dams on Glacial Lake Missoula created large, temporary lakes in low-lying basins along the Columbia. The Willamette Valley was thus flooded dozens of times, depositing rich lacustrine soils that grew to prairies when the flooding ended. The original vegetation of these prairies is long gone, plowed under by settlers who arrived on the Oregon Trail. Large tracts of floodplain forest—Black Cottonwood, Oregon Ash, Bigleaf Maple, Garry Oak—still thrive adjacent to the Columbia, notably at Ridgefield National Wildlife Refuge. Diked fields at this refuge and elsewhere in the lowlands support high numbers of waterfowl, raptors, and Sandhill Cranes in migration and winter.

The Cascade Range occupies the eastern half of the area. Most of this territory, with typical Wet Side forests, is in the Gifford Pinchot and Mount Baker-Snoqualmie National Forests and the Mount Saint Helens National Volcanic Monument. Many of the national forest lands are subject to timber sales, but significant parts are permanently preserved in wilderness areas. Other stands of old growth survive on Forest Service lands—for example, along the Lewis River above Swift Reservoir. Numerous sites around Mount Adams and Mount Saint Helens provide forest birding as good as any in Western Washington.

The ancestral Columbia River maintained its course westward to the Pacific as the Cascades were slowly uplifted, carving the deep Columbia Gorge. The gorge was further widened as powerful floodwater torrents swept through the constriction following the repeated failures of ice dams on Glacial Lake Missoula. The flood crest averaged 1,000 feet high at the east end of the gorge, lessening to 500 feet at the west end. Today the Columbia Gorge is a notable migration corridor for birds and for remnants of the once-epic salmon runs. It is also an important site for wintering waterbirds.

Precipitation varies greatly within the region. Cathlamet, near the ocean, receives an average of 80 inches annually. The central lowlands receive 45–60 inches, rising to 70 inches at higher elevations of the Cascade foothills.

Vancouver receives just 39 inches (the same as Seattle), but in the heart of the Columbia Gorge 46 miles east, Stevenson averages 84 inches annually. Eastward through the gorge precipitation gradually drops off.

Marine low-pressure systems moving east bring heavy winter rains to the west end of the gorge. High pressure east of the Cascades drives gale-force winds westward through the gorge, bringing hot, dry air in summer and cold, continental air in winter. Sometimes the two opposing systems meet in winter, and when this happens, the west end of the gorge can see ice storms and blowing snow. Strong, steady winds in summer and fall make the gorge a renowned windsurfing site. But they can also hamper birding.

Temperatures are much the same as elsewhere in Western Washington. Means for Centralia and Vancouver are 39–40 degrees in January and 65–66 degrees in July.

The two trans-Cascades highways are open all year, although US-12 across White Pass is subject to snow-clearance closures (usually brief). SR-14 through the Columbia Gorge, and other lowland roads, may be made hazardous by ice and snowfall.

Accommodations and services may be found in the Vancouver/Portland metropolitan area, in cities and towns north along the I-5 corridor, and also in a few communities along US-12 and the Columbia.