Abstract: A bird feeder has a containment housing and a convertible feed port assembly mounted through a housing opening. The feed port assembly includes a feed port having a port plate and a support frame which extends into the housing through the port opening. The port plate defines a port opening aligned with the housing opening to enable access to the bird feed within the housing. The feed port assembly also includes a door slidably and rotatably mounted in the feed port. In a retracted position, the door is supported by the support frame in the housing and leaves the port open to provide access to seed within the interior of the housing. The retracted door cooperates with the support frame to form a roof or baffle to prevent seeds from falling out of the port opening. The door is slidable outwardly from the housing interior and rotatable to overlie and close off the door opening. The door has a relatively small aperture for access to small bird seed when the door is closed.