Urban Dictionary defines put out as the dispensation of sexual favors. Of course, that definition has nothing to do with this totally innocent retro-style design for back yard birders who enjoy putting out food for the birds.
Here is a whimsical vintage image of children feeding birds. They are also enjoying the company of a hungry squirrel. The caption below is birder and backyard bird lover humor at its finest: I Put Out For Birds. This is great for anyone who's easy -- about feeding the birds.