Weight censored to close when squirrels land on it but birds are light enough where they can still feed. A good value feeder that attracts a wide variety of birds. Consider the Squirrel Buster Plus for double the seed capacity, more cardinals, and the ability to adjust the weight censor. Or the Hanging Cylinder Feeder with Dome (must use with the Flaming Hot Feast Cylinder to be squirrel proof). Lifetime Warranty. We fix it for free at our shop in Crystal Lake!