The ornamental design for a chickbrooder, as shown and described.
FIG. 1 is a front perspective view of a chick brooder;
FIG. 2 is a front elevation view thereof, the rear elevation view being a mirror image of FIG. 2;
FIG. 3 is a left side elevation view thereof;
FIG. 4 is a right side elevation view thereof;
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken lines consisting of evenly spaced lines in the drawings depict portions of the chicken brooder that form no part of the claimed design, while the broken lines consisting of dash-dot-dash lines in the drawings depict the boundary of the claimed invention and it is understood that the claim extends to the boundary that forms no part of the claimed design.