Various methods have been used for the identification of individual birds under field conditions. Many of the devices described by ... were designed to provide information supplemental to that obtained from the recovery of Fish and Wildlife Service leg bands and to do so without the necessity of recapturing or killing the bird. In 1967 I initiated a project designed to determine the migration routes, winter ranges, and dispersal patterns of Ring-billed Gulls (Larus delawarensis) from various Great Lakes populations. Adult gulls were cannon-netted in two Michigan breeding colonies, one located near Rogers City (Presque Isle County) on Lake Huron and the other on Ile aux Galets (Emmet County) in Lake Michigan. In addition to Fish and Wildlife Service leg bands 2545 plastic wing-markers were attached to adult gulls between 1967 and 1970. This paper describes the marker and briefly evaluates its contribution towards realization of the project’s goals. Reports summarized herein were received between June 1967 and May 1970. Birds marked during the 1970 breeding season are not included in the tabulations.