Squirrels can’t figure out how to open the feeder. It has a lock top you push down and turn to fill. The tube will hold a lot of seed and is long enough so that squirrels can’t hang upside down to reach the feeding ports. The Squirrel Buster also has a cardinal ring so cardinals can sit and eat comfortably or if you just want smaller birds, the ring can be removed.
When a squirrel tries to eat from the feeder his weight closes off the feeding ports to deny him access to the food. You can also adjust the tension to make it sensitive enough to shut down on the large starlings or blackbirds. Backyard birds average 0.3 – 2.0 ounces while blackbirds are about 4 ounces and squirrels are about a pound.