How it works
The handwheel turns an 8-rod lantern pinion that meshes with a 24-peg crown wheel, so the cam shaft turns once for every three turns of the crank. A 20-tooth gear on that shaft drives a 30-tooth gear on a second shaft, which carries the head-turn cam at two-thirds speed. Because the two shafts are out of step, the bird never repeats the same sequence for nine turns of the crank.
Each cam pushes down on a roller fitted to a long wooden follower lever. The lever magnifies the cam's lift and pulls a waxed linen string, which runs up the column through brass guides and into the bird's hollow brass legs. A coil spring on each lever pulls it back up, keeping the roller pressed against the cam.
The stepped head-turn cam gives the quick look-and-hold of a real songbird: flat dwells where the head stays still, separated by steep rises where it snaps to a new angle. Tight clusters of lobes give the beak chatter and wing flutter.