Which revision best corrects the errors in the given sentence?

birds outside at the feeder such as cardinals, finches, and chickadees keep the cat entertained at the window for hours.
a.
birds outside at the feeder: such as cardinals; finches; and chickadees, keep the cat entertained at the window for hours.

b.
birds outside at the feeder—such as cardinals, finches, and chickadees—keep the cat entertained at the window for hours.

c.
birds outside at the feeder, such as cardinals, finches, and chickadees—keep the cat entertained at the window for hours.