The ornamental design for a cover for birdfeeder, as shown and described.
FIG. 1 is a perspective view of a cover for bird feeder showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is another perspective view thereof, but shown in a usage state in an environmental view.
The broken lines illustrate portions of the cover for bird feeder that form no part of the claimed design. The broken lines shown in FIG. 8 depict environment and form no part of the claimed design.