I claim the ornamental design for a feeder for birds, as shown and described.
FIG. 1 is a front elevational view of a feeder for birds showing my new design;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a perspective view thereof;
FIG. 8 is a second perspective view thereof; and,
FIG. 9 is a third perspective view thereof.
The broken lines in FIG. 9 depict exemplary components that might be used in conjunction with the feeder for birds that are shown for purposes of illustration, and form no part of the design claim.