This morning, while recording in the Kettle Moraine State Park, Waukesha Co, WI, I was lucky enough to get recordings of a Red-tailed Hawk and a Blue Jay mimicking a Red-tailed Hawk:
I’ve read the opinion that this common call of the Blue Jay is just coincidentally similar to the Red-tail’s call, but after viewing these sonograms together I have no doubt it is mimicry. Note especially the similarity between the last calls of each.