Their heads were underwater; occasionally, their eyes came above the surface, but mostly they stayed down. Somehow, they were getting breaths, but I couldn’t see how. True, their nostrils are near the base of the bill, and maybe only an instant is needed. These ducks, two males and a female, were swimming fast. The body plumage said Northern Shoveler. The males had cinnamon-brown sides, white in front and behind the cinnamon patch. The heads appeared black, showing, though, as green when the light was right, and their backs dark. The female was streaked brown and light, like so many female ducks. But I hadn’t seen their bills, those large spatula-like projections. Ornithologists created the genus Spatula for these and their three close relatives in honor of that bill.
I’d come to the Union Bay Natural Area at UW’s Horticulture Center to look for them and see if I could watch them feed on this April morning. During spring in Seattle, shovelers are often on the Central and Carp ponds. Most would be paired by this time and traveling as a unit or in small feeding groups. Finally, one raised its head entirely out of the water and showed that humungous projection. I always think that bill should cause them to fall over, but its structure makes it surprisingly light, and I suspect they have strong neck muscles.
They use their bill to filter out food. These birds suck water through the front of their beaks and push it out through the lamellae on the sides. They specialize in small nektonic invertebrates, which is the scientist’s way of saying swimming critters. Probably, Daphnia and many other minute things fill the water column in these shallow ponds. These shovelers swam in straight lines, occasionally doing turns, moving their heads up and down in jerky motions. A few weeks ago, pairs were swimming in tight circles. That behavior probably stirs the crustaceans and other invertebrates, seeds, and microscopic vegetation up from the bottom, making them better for filtering. We’d had strong winds in the last couple of days, and the water column was probably well mixed.
Once, a year ago, on Carp Pond, I watched some shovelers swim in an oval. The oval swimming, as well as the circling, are cooperative feeding techniques. It is an ingenious way of working together, everyone benefits. They can exploit the stirred-up food items by following, filtering out the good pieces. For example, we filter out noodles and vegetables from soup by pulling a spoon full along the side of the bowl and letting the liquid drain out. These ducks suck in a mouthful of soupy pond water and then use their tongue to push the water out through their built-in sieve.
At the eastern end of Carp Pond, I found a shoveler pair actively preening. The female floated in the water, using her bill to pull through the body, wing, and tail feathers, occasionally taking a vigorous splashing bath. The male stood on a log, using his bill to work all its feathers. This log must be a favorite perch for ducks. A week ago, a female shoveler had her bill tucked under back feathers on one end, two Green-winged Teal were preening in the middle, and a drake shoveler was on other end.
I find it amazing that the skin on these ducks is dry. Water doesn’t get to their skin even when swimming. The tight barbules on each feather vein act like Gore-Tex, and the weaves are so close that water droplets can’t get through. The layers of feathers and the coating they put on their feathers make the plumage waterproof. A drop of crude oil on the plumage negates all this and allows water to seep through the plumage, reaching the skin. Birds that encounter an oil spill will vigorously try to preen off the oil. The oil is toxic, but often they die of hypothermal because of the water that reaches their skin, chilling them. Just a dime-size dot of oil may spell their death.
Birds spend a lot of time each day taking care of their feathers. Probably, these two were well fed and preparing for an afternoon nap, if not the night. Once they felt they had thoroughly cleaned and straightened their feathers, it would be time to sleep. We do something similar before bed each night.