The ornamental design for a birdskate, as shown and described.
FIG. 1 is a top and left side perspective view of the bird skate showing my design.
FIG. 2 is a left side view of the bird skate of FIG. 1.
FIG. 3 is a right side view of the bird skate of FIG. 1.
FIG. 4 is a front view of the bird skate of FIG. 1.
FIG. 5 is a rear view of the bird skate of FIG. 1.
FIG. 6 is a top plan view of the bird skate of FIG. 1
FIG. 7 is a bottom plan view of the bird skate of FIG. 1; and,
FIG. 8 is a left side view of the bird skate of FIG. 1 shown with a training draw bar attached to the front side thereof.
The broken line showing of the training draw bar is included for the purpose of illustrating environmental structure and forms no part of the claimed design.