72 Microseasons of the Pacific Northwest

By the first week of September, the fall raptor migration along the Cascade ridgelines is underway, building toward its October peak. Two dedicated hawk-watch sites in the Pacific Northwest document this migration: Bonney Butte on the southeastern flank of Mount Hood in Oregon (elevation 4,800 ft) and Chelan Ridge in the Okanogan-Wenatchee National Forest in Washington. Both are operated in partnership with HawkWatch International and have accumulated decades of continuous count data. Sharp-shinned Hawks (Accipiter striatus) are typically the most numerous species counted, followed by Cooper's Hawks (Accipiter cooperii), Turkey Vultures (Cathartes aura), Red-tailed Hawks (Buteo jamaicensis), and American Kestrels (Falco sparverius). At Bonney Butte, up to 18 species of raptors have been recorded in a single season, with totals averaging around 2,900 birds annually. The peak at Bonney Butte is typically the last week of September through the first week of October. Golden Eagles (Aquila chrysaetos) move along the Cascade crest in September, following updrafts above the high ridges. For observers, both sites are accessible by trail or road. Bonney Butte (via the Bonney Meadows Trail in the Mt. Hood National Forest) can be reached by passenger car, and volunteer counters welcome visitors who want to watch and learn identification during the September–October count season. The experience of watching a steady trickle of hawks gliding south along the ridge — sometimes several in the air simultaneously on good migration days — with the entire Cascade landscape spread below, is one of the Pacific Northwest's most compelling autumn spectacles. The migration behavior of raptors is highly sensitive to weather: cold fronts push birds south en masse, while calm, warm periods slow movement, teaching observers to read the sky and wind for migration conditions.