Convicts

There were three escaped convicts running from the police. With the police right on their tails, the convicts run into a forest and decide to climb trees to hide. The police run into the forest in hot pursuit, only to lose track of the convicts. Suddenly, one of the officers looks up and sees the shadow of one of the convicts in a tree.
He alerts the other officers and asks, "What's that up in the tree?" The convict thinks quickly and replies, "Hoooo Hoooo!"
The officers promptly think, "Awww, it's only an owl." So, they walk on, and stop when they spot another shadow in a nearby tree.
The second convict, thinking that the first guy had the right idea, replies, "Meowww."
The cops think, "Great, it's some poor cat stuck up there" and walk on. After another few minutes, the eagle-eyed officer sees the third convict and confers with his fellow officers. The third convict, seeing his cohorts good luck, decides to try the same method to fool the police below.
So, he bellows at the top of his lungs, "Mooooooo!"