The Bluebird feeder is unlike others in that the bird enters a hole to obtain its food, be it seed, nuts, berries, etc. The transparent walls enable the host to see the birds as well as keep track of how much food is left. This feeder is a good idea if you already have nesting Bluebirds in the area. Other birds may also build up the courage to go in the hole. The hole is small enough to keep out less desirable birds such as Starlings, Graclkes and Cowbirds.