The circular radar echo pattern you see develop on clear nights after sunset is indeed bird migration. It is the nocturnal migrants taking off for the night.
see below for more info on radar ornithology. http://virtual.clemson.edu/groups/birdrad/ ________________________________ From: Scott Brim <[email protected]> To: Alicia Plotkin <[email protected]> Cc: CAYUGA_BIRDS <[email protected]> Sent: Mon, April 11, 2011 9:40:26 AM Subject: Re: [cayugabirds-l] migration on radar? On Sun, Apr 10, 2011 at 22:40, Alicia Plotkin <[email protected]> wrote: Hi, > > I just checked the weather forecast for tomorrow, and noticed the radar >had >roughly concentric circles of increasing density centered on the radar site in >Binghamton. (Radar is here, but it automatically updates so you may not see >what I did at 10:30 PM.) Is that migrating birds? > > "Ground clutter" is common within 20 miles of a radar source. Wikipedia says: "Clutter (also termed ground clutter) is a form of radar signal contamination. It occurs when fixed objects close to the transmitter—such as buildings, trees, or terrain (hills, ocean swells and waves)—obstruct a radar beam and produce echoes. The echoes resulting from ground clutter may be large in both areal size and intensity. The effects of ground clutter fall off as range increases usually due to the curvature of the earth and the tilt of the antenna above the horizon. Without special processing techniques, targets can be lost in returns from terrain on land or waves at sea." -- Cayugabirds-L List Info: http://www.NortheastBirding.com/CayugabirdsWELCOME http://www.NortheastBirding.com/CayugabirdsRULES ARCHIVES: 1) http://www.mail-archive.com/[email protected]/maillist.html 2) http://birdingonthe.net/mailinglists/CAYU.html 3) http://www.surfbirds.com/birdingmail/Group/Cayugabirds Please submit your observations to eBird: http://ebird.org/content/ebird/ --
