It is interesting to me that the Great Horned Owl nesting sites that have been reported around St. Louis recently (and on time) are using a tree cavity(Forest Park), an apparent hawk nest(Dave Pierce's sighting in Chesterfield Valley) and an open snag(Wild Acres Park-Overland, Mo).  Text book yes, but a fun study, too.
Bryan Prather
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St. Louis Co., Mo.
The Audubon Society of Missouri's Wild Bird Discussion Forum
ASM Spring Meeting: April 27, 2012 in Joplin, MO
ABA Birding Code of Ethics