Weather maven and Baltimore Sun colleague Frank Roylance reports that the National Weather Service in Sterling, Va. picked up some unusual patterns in its radar earlier this week.

An odd bluish ring showed up on the radar screen around 6 am in the upper Chesapeake near Pooles Island, and then expanded across the area, Frank reports in his Maryland Weather blog.  At left is one of the radar images.

The weatherman thought it might be birds. They're likely purple martins, according to Jerome A. Jackson, professor of ecological science at Florida Gulf Coast University (and father of Baltimore Sun photo editor Jerry Jackson).

"They gather in enormous flocks prior to migrating to the Amazon basin for the winter ... and usually roost near large bodies of water where they then move out to feed on the hordes of insects that are produced in the area," Professor Jackson emailed Frank.

Are there any early risers out there who can confirm that weather radar is picking up a huge flock of birds getting up as dawn arrives?