The Pacific Bushtit and Interior Bushtit populations differ visually and apparently have relatively little contact, as they are largely separated by major ecological barriers to bushtit dispersal, such as the Sierra and the Cascades. Even though Bushtits are considered relatively sedentary, both populations are expanding their range, creating the possibility of increased contact, particularly in areas where the barriers to dispersal are not as significant, such as the Klamath Basin, the lower passes in the Cascades and the Columbia Gorge.