A couple weeks ago, I set up a bird feeder outside my living room window. It took almost a week before any birds noticed it. And, as it turned out, it wasn't a bird that found it first. The birds didn't notice the food until after a squirrel had started tearing into the seed bell. At first I was annoyed at the squirrel, but then I realized that he was eating only one type of seed and scattering the rest onto the roof for the birds to eat.
There seem to be only two types of birds here: sparrows and one blue jay. The blue jay sits in the tree and yells at the sparrows until they make room for him. The squirrel pretty much ignores the birds and focusses on getting his prefered type of seed out of the little cage they're in. I had to use a metal twist tie to keep him from opening the cage door. I tried a string, but he pulled that open.
When the bird seed was all gone, the squirrel climbed up on the metal bar, looked at me somewhat insistently, and made a loud knocking noise. Pushy little critter. Smart too. He knew that the cats couldn't get him through the glass, and he certainly seemed to know that I was supplying the food. The birds were just opportunists, but the squirrel makes things happen.