With spring migration picking up, bird collisions with windows and other
structures will be picking up. The American Bird Conservancy is
stepping up its attention to this issue and has a portion of its web
site devoted to collisions.

http://www.abcbirds.org/abcprograms/policy/collisions/glass.html

Also, you may wish to test your identification skills on the 17 species
shown at the beginning of this site.
Noel Cutright, Ozaukee County