The term 'Puzzling Bird' can be solved by the crossword solution MERL, which is a four letter word. MERL is an acronym for the Migratory Bird Treaty Act, which was passed in 1918 and is a federal law that protects migratory birds from being hunted or killed. The act also regulates the hunting of migratory birds and their eggs, as well as the sale of feathers and other bird parts. The act is enforced by the U.S. Fish and Wildlife Service, and violations of the act can result in fines and jail time.