Shorebirds need special tools to probe the mudflats
In late July I made a short visit to Emigrant Lake to see if any water might remain to encourage shorebirds from the tundra to drop in for a short visit before continuing on to sunny tropical shores for the winter.
There wasn’t much, water that is. As a kid I doubt whether I could have collected enough mud on my face and clothes to elicit comment from my mother, and I was very good at attracting mud.
Still, there was a modest assemblage of shorebirds. There were a handful of small western and least sandpipers, plus a greater yellowlegs. My favorite was the long-billed dowitcher.
The dowitcher is a relatively large shorebird with an overly long straight bill. To my students I referred to dowitchers as the sewing-machine of the mudflats as they rapidly and repeatedly probe deep in the mud for edible wiggly things.
It’s then I recalled being with a biologist as he mist-netted and banded shorebirds. As I removed a western sandpiper from the net, I touched its bill. I recoiled a bit. It was soft, not like the hard beak of a chicken or a robin or a red-tailed hawk. I thought something was wrong with the bird until I sorted through my mental files.
Of course, the bill of a probing sandpiper is different. It probes in the mud where it can’t see its prey. It feeds by touch. The bill is covered with soft and sensitive tissue allowing it to sense something edible in the muck. Specimens resting on museum trays don’t show this. The bills are dry and hard like those of a chicken. There are other shorebirds that pick up their food from the surface, including least sandpipers and semipalmated plovers, and their bills, too, are hard, being more as one would expect.
If you think about it, the bill of a probing sandpiper has to be remarkable in another way, especially a species with a bill as long as that of the dowitcher. What happens when the dowitcher touches a food item deep in the mud? Imagine one trying to open its bill to grab the prey. It can’t be easy when stabbed deep.
Unlike mammals, many birds have a movable upper jaw. The palate (roof of the mouth) slides along another bone coming down from above. This sliding joint has the effect of bending the tip of the upper mandible upward a bit when the palate slides forward. The first time I saw a relaxing godwit do this when not feeding, the “bent” upper mandible looked very strange. (A godwit is another shorebird with an extremely long bill for probing.) However, it explains how a probing shorebird can open just the tip of the bill while buried deep in the mud and grab a tasty morsel.
It’s stories like these that make me wonder how many little events I watch in nature that seem so normal, like the feeding of the dowitcher, but which conceal fascinating behaviors and other adaptations that we usually overlook. There is always something new to learn.
Stewart Janes is a retired biology professor at Southern Oregon University. He can be reached at email@example.com.