Yellowlegs and the Perpetual-Motion Toy Bird | WCAI

Yellowlegs and the Perpetual-Motion Toy Bird

May 29, 2018

Yellowlegs and the bird toy of Robert's youth
Credit Franco Folini / flickr / / Amazon

The other day, crossing Uncle Tim’s Bridge, I saw a flock of fourteen yellowlegs feeding in the gray slurry of the mud flats of Duck Creek at low tide.  Greater and lesser yellowlegs are two of our most readily- identifiable local shorebirds. They are by far the largest of the sandpipers, with stilt-like bright yellow shanks that give them their common name. Their call is an unmistakable three-note descending whistle: CHOO-choo-choo, CHOO-choo-choo.


Still, it is difficult to tell the two species apart unless they are standing together. (I decided to call these birds greater yellowlegs, in part because they are more common than the lessers in spring migration, and also because there was no one else there to tell me otherwise.) 

Yellowlegs have a clean, smooth, sculpted look, as if they were painted decoys of themselves. I was struck by how gracefully they moved over the mud flats, how they transitioned seamlessly between walking on the mud, then slipping into the shallow currents running seaward on the outgoing tide, riding like little boats on the water. They poke and jab in the mud, as if they could sense small worms and other invertebrates in the thick slurry, though how I can’t imagine.  

As they fed they stayed in a loosely-cohesive flock, not crowding one another, but remaining in visual and psychological touch, like alewives in a brook. Every now and then one would begin flapping rapidly in the water, bathing, I assumed, while the others would gather around it, like a circle of young urban teenagers watching one of their group engaged in show-offy break dancing. 

They also exhibit a characteristic tic: a sudden snap of the head forward every few seconds, that makes them seem like mechanical toy birds. In fact, they reminded me of those fascinating drinking bird toys of my youth – you remember, the ones that stood on red-booted plastic legs, had a green, liquid-filled glass tube for a body, and a red, felt-covered head that sported a plastic top hat. You placed the bird in front of a bowl of water and dipped its beak and felt forehead into the water. After a few seconds, the bird raised its saturated head, and, after another few seconds, miraculously dipped its head back into the bowl again. It did this over and over for as long as water remained in the bowl in front of it. It seemed a bit of sorcery – a transparent example of what we were always told was a physical impossibility: perpetual motion.  

Even as a boy, I could see that the trick had something to do with capillary action, evaporation, and careful balancing of liquids inside the glass body of the bird. But I could not, and still cannot, quite figure out the exact process by which the thing worked. It seemed something truly magical, and I remember thinking that if I could just place a small dome over the bird and the bowl to catch and condense the vapor evaporating from the bird’s head and channel it back into the bowl, it would be a truly endless and perpetual cycle, like the rains on the earth.  

I did not have enough schooling then to realize the deeper truth that the toy exhibited, which of course is that the evaporation process which made the bird dip and rise is, in fact, driven by the sun, as are the rains, as are these yellowlegs in the creek probing the mud flats for mollusks and worms, as indeed is everything on the earth driven by the sun. It would be years before I learned not to take the sun for granted, or to wonder, in Robert Frost's words, if "there is something that is sending up the sun."