The ornamental design for a bird feeder frame, as shown and described.
FIG. 1 illustrates a top, front, right side perspective view of a bird feeder frame of my design, the center post being shown fragmented as being of indeterminate length; and,
FIG. 2 is left side, rear elevational view of the bird feeder frame as shown in FIG. 1, the bottom view being plain and unornamental and not forming a part of the design.