One of the first things beginning birders learn is when they hear what they are sure is a red-shouldered hawk, they cannot be certain the call is that of a red-shouldered hawk. The reason for this is blue jays often mimic the call of this well-known predator.
Recent research has revealed much about the mimicry practiced by the blue Jay. For example, we now know blue jays do not just mimic red-shouldered hawks. The truth of the matter is they also mimic other predators such as the osprey and Cooper’s hawk.
It is apparent that blue jays mimic the call of the red-shouldered hawk in an effort to warn other jays living nearby that a predator is in the neighborhood. However, some ornithologists believe that blue jays may also mimic the call of a hawk in an effort to scare other birds such as grackles enough that they drop their food as they make a hasty flight to cover. Once the bird leaves, the blue jay can fly down and consume the acorns or other food left behind by the startled birds.
If you have a theory that helps explain why blue jays mimic hawk calls, I would love to hear it.