Several of you have asked about NexRad and nocturnal bird migration. What is it? Where is it? How does it work? By utilizing on-line weather resources for wind direction and radar, I can generally predict if the following morning is going to be gangbusters or just mediocre for birding. Radar can't tell you which species are migrating, only that migration is occurring. Just after dusk, if winds are favorable for migration (calm, or northerly in the fall and southerly in the spring), millions of birds will take wing – this is the exodus. Think of birds as giant raindrops - Doppler radar reflects off the moisture on their bodies. As long as the weather remains favorable throughout the night, migration will reach a peak by the time most of us are sound to sleep. By the early morning hours, after having flown 100 miles or more, birds in mixed flocks will break out of migration and start looking for a place to forage and rest. This is why there is a strong feeding peak early in the morning – the birds are coming in to refuel. There is also a feeding peak of activity before evening exodus.
Link: How to use NCAR NEXRAD
Link: NCAR NEXRAD
Link: Ornithology Radar Tutorial
Link: Tutorial section on Migrating Birds
Link: Wind Velocity/Direction
Link: Using Radar to Save Birds
Eastern Bluebird image © 2007 Mike McDowell