Brian Menker sent me the following link about radar images and bird roosts. I agree with him that I don't think all of these rings could be due to Purple Martins. I have never heard anyone reports such large roosts of Purple Martins in Ohio. The only large roost in the area that I have heard of is one at Presque Isle, Pennsylvania. Brian's comments are below. Doug Overacker Springfield, Ohio http://www.erh.noaa.gov/iln/research/birds/ They make some interesting observations about radar "rings" that appeared on several mornings in early August, that they claim are due to roosting birds. Specifically, they speculate that they are due to huge roosts of Purple Martins that return to the same places at night and create radar rings in the morning as they leave to feed for the day. I find this conclusion to be highly doubtful. The number, size, and scale of the "roost rings" on their example loops from early August would indicate many massive roosts of martins that we just don't see. If there were that many roosts of Purple Martins numbering in the tens of thousands, birders would be reporting them. I don't have my Peterjohn copy handy, but I don't remember ever hearing of those types of roosts here in Ohio. I think these rings are artifacts of specific atmospheric conditions and ground scatter. They even say that the rings show up in the morning and not the evening because the atmospheric conditions are more favorable for the radar beam to hit lower objects. I wanted to post something on this to Ohio Birds to let everybody weigh in, but I'm not set up to post anymore. I know there are discussions on radar detection of birds from time to time, and I think feedback from Ohio's birders could help the Weather Service see that their speculations are a bit wild. Could you at least post the link and throw it out there for comments? If any bird roosts in Ohio would create a radar ring, I would think that the crow roost here in Springfield would show up on winter mornings. There are tens of thousands of them, and they are much bigger reflectors than martins. Maybe I'll keep my eye on the radar when they show back up for the winter. Brian ______________________________________________________________________ Ohio-birds mailing list, a service of the Ohio Ornithological Society. Our thanks to Miami University for hosting this mailing list. Additional discussions can be found in our forums, at www.ohiobirds.org/forum/. You can join or leave the list, or change your options, at: http://listserv.muohio.edu/scripts/wa.exe?LIST=OHIO-BIRDS Send questions or comments about the list to: [log in to unmask]