Late September sits in the heart of fall bird migration across much of the United States. Nighttime flights of warblers, thrushes, and other songbirds peak as cold fronts push birds south along the Atlantic and Mississippi flyways. BirdCast’s radar-based forecasts show nightly migration intensity for birders and city managers who want to time Lights Out campaigns when millions of birds may be overhead after dark.

Audubon’s Lights Out guidance asks buildings to dim or shut nonessential lights from about 11 p.m. to 6 a.m. during peak migration windows, because artificial light draws and disorients night migrants. The same network’s collision tips push high-contrast markers on exterior glass, screens, or cord curtains so daytime reflections do not look like open sky. U.S. Fish and Wildlife Service glass-collision resources treat window strikes as a monitoring and mitigation problem for campuses, refuges, and cities that want local data — not a one-day news spike.

Journey North’s volunteer maps still track monarch butterflies, hummingbirds, and other seasonal movers for classrooms and backyard watchers. Peak songbird nights often run from mid-September into October; monarchs and raptors stretch later into fall. Simple home steps — lights down overnight, feeders close to glass or well away from it, and curtains at night — cut risk without waiting for a city ordinance. Parks and refuge birding lists also pick up as waterfowl and shorebirds begin their own southbound push.

Accounts agree fall migration is active now and that lights plus glass are the main urban hazards. They differ on tools: BirdCast and Journey North emphasize real-time tracking; Audubon and FWS emphasize building and window fixes.