That little chickadee is looking angry. What the sign is not saying is that if you feed the birds (including the rats with wings), then the real rats are going to come and scavenge the leftovers. That’s why they don’t want you feeding our feathered friends.
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That little birdie looks like he could have gotten work with Alfred Hitchcock about 40-odd years ago… totally looks ready to take a nip out of Tippie Hedren, given a chance!