I know that Blue Jays issue convincing imitations of Buteo calls.  I 
certainly know that a heard Red-shouldered can't be counted on!   Today I 
was thrown a real curve ball, a Blue Jay giving a "kek" call that was a 
perfect (to my ear) rendition of a Cooper's Hawk call.  I've just had a look 
on the BNA account for the Blue Jay, and as far as I can tell, the issue of 
imitating hawks is not dealt with at all.  Just wondering if anyone else has 
ever noticed Jays imitating Accipters, and to issue a warning:  that 
Cooper's Hawk you thought you heard, may not be one after all.

Kurt Schwarz
HowCo
goawaybird at comcast dot net