Spring migration, explained simply

Each spring, hundreds of species pour north across North America to breed. It's the busiest, richest stretch of the birding year — and it moves faster than most people expect.

Why they move

Migration is about food and daylight. As the north thaws, insects explode and days lengthen, opening vast feeding and breeding grounds that are frozen and dark in winter. Birds that spent the cold months in the southern US, the tropics, or South America ride that green wave north.

It happens in waves

Migration isn't a single event; it's a series of pulses tied to weather. A warm front with southerly winds can drop a big fallout of migrants overnight, and a cold snap can stall everything for days. That's why the timing charts on BirdMap show a curve, not a single date — the peak is your best bet, but the whole window is live.

How to be ready

• Check the peak week for your target species in your state, and plan around it.
• Get out early — songbird migrants are most active in the first hours after dawn.
• Watch the weather: mornings after a warm, southerly overnight flow are prime.
• Learn a few songs ahead of time; in spring you'll hear far more than you see.

Where to start

Pick a species you'd love to see and check its arrival timing in your state on its migration page, or scan the most-observed birds where you live and watch for newcomers as the season builds.