To clarify the title: This bird is imitating our cat at this very moment. He does that to scare all the other birds away, and it works like a charm! Sometimes he even adds the "ground foe" call of blackbirds if some stubborn sparrows still persist. The pose and the eyes show that he's very agitated, he's actively pretending for benefit. He's lying! He's so good at it that I sometimes step outside and call the cat just to see a startled jay flying away.