well.
Just heard what sounded like a red-shouldered hawk, but way lower in a small tree than I'd expect. Waited and suddenly a small female Steller's Jay hopped out onto a branch, making like a red-shoulder several times before settling down to work the bark - eating grubs or bugs of some kind I guess, not only yelling like a hawk but eating like a flicker!
I hadn't been aware of mimicry by jays so did some googling and found a couple of references:
the birdchat archives here listserv.arizona.edu/cgi-bin/wa note that "Steller's Jay imitates both Red-tail and Red-shouldered very convincingly...Ken Burton"
and
www.naturesongs.com/tyrrcert.html#corv notes "Steller's Jays (Cyanositta stelleri) are common residents of coniferous forests in the Western US. This one gives us a sampler of his vocalizations from his perch in an Arizona Cypress near Sedona, Arizona. (378K) Steller's Jays are famous for mimicry, especially of raptors. Here is an example of a Steller's jay mimicking a Red-tailed Hawk near Sedona, Arizona, 3/5/01. (72K) This next example shows some of their parrot-like chatter and calling - easy to see how they might slip into mimicry! (147K)"