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Bird Detection via Doppler Radar
Angie Enyedi (radar animation by Jason Deese)
National Weather Service Jacksonville

Doppler radar transmits pulses of energy into the atmosphere, and when this energy intersects a target, information about the density (radar reflectivity) and motion (radar velocity) of the target is transmitted back to the radar (Figure 1).  Most of the time the Doppler radar beam intersects targets composed of water vapor, including clouds, rain drops and hail stones. Meteorologists utilize this data from the radar to interrogate storms, which makes the Doppler radar a critical component of the proactive severe weather warning service that the National Weather Service (NWS) provides.

Sometimes, the radar beam intersects other objects, including birds.  When there is a high density of birds in one location, typically during bird migrations, sometimes as the birds take flight the radar beam intersects the flock.  This happened in several locations across coastal Southeast Georgia on the morning of October 25, 2009, right around sunrise.  This is a favored time for birds, particularly waterfowl, to leave their nocturnal nesting sites on bodies of water to either continue their migration or return to their favorite daytime refuges.

The animation (Figure 2) illustrates two large and one smaller area of birds taking off, as detected by the NWS Jacksonville Doppler radar. In addition, there is a Google Map (from Google Earth) to reference for location (Figure 3).  It appears as though the southernmost flock arose from the Satilla River near Woodbine, while the other flock ascended from a tributary of Buttermilk Sound, just west of Little St. Simons Island. A third, but smaller flock, appears to have flown from the western side of Cumberland Island National Seashore.

Many bird enthusiasts utilize radar imagery to track migration patterns. Radar imagery has also been helpful to both birds and humans regarding aviation safety. Most airport terminals use radar data to track birds as they cross flight paths to avoid collisions.

Click here for more information on the NWS Doppler Radar.