Jack puts 1/3 pound of seed in the bird feeder each time he fills it. How many times can he fill the bird feeder with four pounds of seed?

The number of times Jack can fill the bird feeder with four pounds of seed is (4 pounds / 1/3 pound/time) = 4 * (3/1) = <<4*(3/1)=12>>12 times. Answer: \boxed{12}.