Why a duck’s head shape might vary from the picture in your field guide
Published: October 21, 2011
If you are watching ducks this winter, trying to sort out the differences between scaup and Redheads, or Barrow’s and Common Goldeneyes, or any number of other species, you will undoubtedly be studying head shape.
FORM FOLLOWS FEATHERS: A Greater Scaup that has fluffed its head feathers (left) appears to have the classic rounded shape, while a bird that has compressed its head feathers shows a different and less distinctive contour.
Art by David Allen Sibley
Field guides and other birders will advise you to look for the puffy rounded head of Greater Scaup and Redhead, the sloped forehead of Canvasback, the squared-off crown of Lesser Scaup. Each is a powerful and time-tested field mark that works very well — most of the time.
It’s important to realize, though, that the skulls of most ducks are the same shape. The bulges and angles we see are produced by slightly longer or shorter feathers on different parts of the head. This means that head contour can change dramatically as the duck raises and lowers its feathers, and this is something the birds do at predictable times.
A duck that is relaxed — sleeping, for example, or preening — will hold its head feathers fluffed out. Its head will be its puffiest and most rounded. On the other hand, a duck that is diving, alarmed, or preparing to take off will press its head feathers against the skull, and, usually, it will stretch its neck up at the same time.
Differences in head shape (due to feather length) are most obvious when feathers are raised and least obvious when feathers are pressed close to the skull.
All you have to remember is that if a duck is alarmed or actively diving, its head feathers are likely to be compressed, and the head shape may not be the typical shape the books tell you to watch for.
Just wait a minute or two. Watch as the bird stops diving and resumes resting, and you will see its head shape change back to a more familiar, and more distinctive, form.
David Allen Sibley is the author of The Sibley Guide to Trees, The
Sibley Guide to Birds, Sibley’s Birding Basics, and Sibley guides to
birds of eastern and western North America.|
Read more by David Allen Sibley.