Birds eat just like the rest of us. They need nutrition in order to be able to live. With eating, they gain strength and that allows them to be able to fly and do daily tasks.
Not sure what's up with the "you're welcome" part. Birds eat tons of things, from regular bird seed put out by humans, bread put out by humans, and also worms, though those aren't put out by humans...I hope. It also depends on the type of bird.
