Monitoring Migration
Migration is a phenomenon that occurs across the world, involving billions of birds moving from the breeding grounds to their wintering grounds and back, across seasons. It is estimated that ~70% of North American birds are migratory and that ~80% of those migrate at night. This makes monitoring their movements challenging. However, many birds produced species-specific nocturnal flight calls (NFCs) while they fly that we can ease drop on to better understand the timing and community composition of species as they migrate across time and space. This emerging field of study of using NFCs is helping scientists make recommendations to decisions makers regarding steps we can take to ensure their passage through our backyards is as safe as possible.
Spring 2025 Migration Tracker
Nightly recordings are processed through ‘Nighthawk‘, a machine learning model for acoustic monitoring of nocturnal bird migration, and then visually examined for accuracy.
*Note that data accuracy is somewhat limited with regard to nightly NFC counts and species identification on a per call basis, but that overall trends are highly accurate.
Below you can view and listen to examples of some of the more common nocturnal flight calls you can hear in the northern Colorado region. We will add more to this gallery as we record them with our NFC station.
Click ‘play’ to listen to our nightly live stream of migration over our Fort Collins, CO office. Live streams begin ~60 minutes after sunset and end ~60 minutes before sunrise. If you visit the page during the live stream period and you get an error saying “This video is unavailable”, try refreshing your browser.
Visit one of our banding stations to see migratory birds up close and in person! Click here to register.
Go Lights Out for Birds!
Nocturnally migrating birds navigate using a number of cues including the earth’s magnetic pull, their senses of smell and memory, starlight and landscape features like mountain ranges and bodies of water. The presence of artificial light from human activity disrupts these abilities and has introduced a relatively new challenge for species that evolved to migrate under the cover of darkness.
Artificial light greatly interrupts the navigational abilities of migratory birds, causing stress and leading to individuals flying off course and even colliding with buildings.
To help prevent this issue, there’s are two simple solutions that everyone can use to help:
- Turn off unnecessary lights at night, especially on nights where a large number of birds are predicted to fly through an area.
- Add decals to your windows to break up reflections of nearby vegetation that may confuse birds and cause them to fly into and collide with windows. These collisions are often deadly and are one of the main causes of bird population declines.
To learn more about this issue and ways that you can help protect birds today, visit birdcast.info/science-to-action/lights-out/.
Check out the daily state and national Lights Out Alerts and migration intensity maps below to find out when high concentrations of migratory birds are predicted to fly over your location so you are aware of when it’s most critical to turn off those lights!
Maps powered by:
Nighttime Bird Surveillance Network
The science and practice of listening to birds migrate at night is still relatively new, with much still to be learned about migratory birds. For a primer on the history of nocturnal flight call monitoring and how you can get involved, listen to the five-part podcast series ‘The Nighttime Bird Surveillance Network‘ written and produced by our Communications Director, Jacob Job, and released by Scientific American.
