Different sized bird feeders are created for different sized birds. Makes complete sense but it's more important than you would think. Larger birds, such as cardinals and mourning doves, tend to feed on hopper-type feeders that release food onto a tray where they can land. Triangular tube feeders, for smaller birds like finches and sparrows, require more agility to sit on a perch, near a hole in order to extract the seed. Now you know why you always see the same type of birds dining at your feeder and what you can do to attract others!