Speaking of Pine Siskins...

By far, the most commonly seen bird visiting the feeder set up by the representatives of Swarovski Optik at the ABA convention at Snowbird were the Pine Siskins. They dominated the feeder and while generally content to sit and much the hulled sunflower hearts for long periods of time, they could also become quite feisty when a newcomer approached. In this image, an established feeder denizen defends against an approaching newcomer. If you look closely you can even see the tongue of the defender extended from his open beak as he lets out a loud, shrill warning call.