A bird feeder is provided with a containing structure including an internal space and at least one feeding opening on an outer surface of the containing structure and communicating with the internal space; a helical structure disposed on the outer surface of the containing structure in the form of a helix wherein pitch is defined as a distance from the crest of one thread of the helical structure to the next thereof; and at least one perch disposed on the outer surface of the containing structure and each disposed directly under the feeding opening.