PORTLAND, Ore. (AP) — Millions of birds have been flying though Oregon as they head north for the summer and most of their journey happens after the sun goes down. Oregon Public Broadcasting reports the Audubon Society shared a “lights-out alert” this week based on data published by Colorado State University’s AreoEco Lab. The lab forecasts bird migration patterns across the country and suggests lights-out alerts based on how many birds are passing overhead. Light pollution can disorient and exhaust birds. Portland Audubon Society conservation director Bob Sallinger says while the bird migration season in Oregon peaks in early June, the migration season can last months, so reducing light pollution at night is always helpful to birds.