I claim the ornamental design for a bird feeder, as shown and described.
FIG. 1 is an elevated front view of the bird feeder, with dash lines depicting suspending means;
FIG. 2 is an elevated side view thereof shown without the broken line showing of the suspending means, the opposite side being a mirror image, with hinged roof panel shown in phantom for illustration;
FIG. 3 is a top plan view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is an elevated back view thereof, with dash lines depicting suspending means; and,
FIG. 6 is a top front perspective view of said bird feeder.
The broken line elements in FIGS. 1, 2 and 5 are for illustrative purposes only and form no part of the claimed design.