Anna’s hummingbirds have expanded their range across the Pacific Northwest region. These small birds established populations in Oregon, Washington, and British Columbia. Numbers remained low for decades before rising rapidly from the late 1990s. Introduced plants and ornamental gardens aided this significant population growth. Climate change may have also supported the species’ northern expansion.Anna’s hummingbirds have expanded their range across the Pacific Northwest region. These small birds established populations in Oregon, Washington, and British Columbia. Numbers remained low for decades before rising rapidly from the late 1990s. Introduced plants and ornamental gardens aided this significant population growth. Climate change may have also supported the species’ northern expansion.