Here is a comprehensive site of bird and radar research from Clemson.
There is a page on roosting rings illulstrated by Purple Martins. Some
years ago (5-10) when I lived in Columbus  there were some posts on
locating Crow roosts by from the rings produced in early morning and in
evening. Perhaps they can be discovered from searching the archives.

http://virtual.clemson.edu/groups/birdrad/index.htm


Rich

Richard Cressman
East Boston, MA
r.cressman.xyz.1928[at]gmail.com

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