A bird feeder has telescopically aligned inner and outer cylindrical housings with opposed surfaces of complementary shape that are reverse tapered in a substantially vertical direction to enable guided vertical movement of the housings with respect to each other. The housings have openings in their side walls which are substantially in alignment when the outer housing is in an upper position and misaligned when the outer housing is in a lower position. A compression spring centrally located about the vertical axis of the feeder is confined within a lower portion of the feeder and biases the outer housing to its upper position. When the outer housing is moved to its lower position by the weight of a squirrel overcoming the biasing force of the compression spring, the housing openings are substantially misaligned such that no significant through opening exists, thereby preventing access to the birdseed.