Large Tube Feeder A tube feeder is a hollow cylinder, often made of plastic, with multiple feeding ports and perches. Tube feeders keep seed fairly dry. Feeders with short perches accommodate small birds such as finches but exclude larger birds such as grackles and jays. The size of the feeding ports varies as well, depending on the type of seed to be offered. Note that special (small) feeding ports are required for nyjer seed in order to prevent spillage.