magpie
鵲 refers specifically to the magpie, a bird known for its black-and-white plumage and noisy chatter.
鵲 combines 昔 (old, past) with 鳥 (bird). The 昔 component likely contributes a phonetic element, as the magpie's call or name may have been associated with a similar sound.
The left side 昔 suggests something old or from the past, and the right side 鳥 is a bird. Picture an old, wise magpie chattering ancient stories.
For シャク, imagine a magpie shaking its tail feathers vigorously: shake -> シャク, and the bird's noisy chatter shakes the air.