Possible Clues:

• Quiver
• Jerk, by implication, is to look for birds
• Appear nervous, supplying toe of newt to necromancer
• Nervous reaction from tense bad speller?
• Quiver spasmodically as in tic
• Sudden jerky movement; pang
• Twinge
• Go looking for rare birds - spasmodic movement
• Move uncontrollably - watch birds
• A spasm of tic