Starting: Mon, Apr 19, 2021, 7:40 PM MDT
Ending: Tue, Apr 20, 2021, 6:10 AM MDT
Peak migration traffic
Here's what happened across this night...
Birds in flight
Birds usually begin to migrate 30 to 45 minutes after sunset, with the greatest number in flight two to three hours later.
Flight direction and speed
Birds tend to migrate northward in spring, but seasonal timing, weather, and geography alter their flight directions and speeds.
Migrating birds regularly fly up to 10,000 feet above ground, although seasonal timing and weather conditions dramatically impact their distributions.
Note: Direction, speed, and altitude may be unreliable when the number of birds in flight is low. In such cases, chart data may include gaps.
And across this season...
Birds in flight (nightly avg.)
During spring migration, most birds pass through the contiguous U.S. from mid-April to mid-May.
Total birds crossed
This is the estimated total number of birds that have fully crossed this region. The curve rises quickly during peak migration and levels off at the end of the season.