Why shape and behavior are among the best field marks for Spotted Sandpiper
Published: July 1, 2008
Among our sandpipers, the "Spotty" is uniquely widespread. It nests over two-thirds of North America and winters commonly in the southern tier. Between those areas, any tiny pond or creek or breakwater is a likely stopover site.
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Somewhat territorial all year, it never gathers in dense flocks like some of its relatives. We'll never see thousands of Spotted Sandpipers in a day, but we'll almost always see a few, bobbing along jauntily in places where no other sandpipers occur.
The spots on a Spotted Sandpiper in breeding plumage, from mid-spring to late summer, make it instantly recognizable. The rest of the time, nearly two-thirds of the year, its identification rests on subtle points. As with all sandpipers, shape and behavior are among the best field marks. A low-slung sandpiper, the Spotted has an elongated body but short legs; a tail that extends beyond the tips of its folded wings; a fairly short neck and small, rounded head; and a bill that is straight, slightly stout at the base, and blunt at the tip.
Just as distinctive as its shape is its behavior. The Spotted Sandpiper generally forages alone, and it flies with rapid, stiff, shallow wingbeats, often low over the water. When standing, it bobs the rear part of its body up and down almost constantly. This teetering in itself would be practically enough to identify it. Along the Pacific Coast, however, the Wandering Tattler has similar body actions, and its winter plumage is similar as well, so it requires a second look.
In addition, sandpipers of the genus Tringa, such as the yellowlegs, often bob their heads and foreparts, especially when excited. Our smallest Tringa, the Solitary Sandpiper, is close to the size of Spotted Sandpiper and often confused with it. A second look at behavior should clear this up, since the Spotted holds its head more or less stationary while bobbing its hindquarters, while the Solitary bobs its head most vigorously.
One of the best plumage points for the winter Spotted Sandpiper is the white mark that notches up onto the shoulder. A narrow white wedge before the bend of the wing, it contrasts with the smooth brown wash at the sides of the chest. Be aware, though, that the white mark may disappear temporarily depending on the position of the wings and arrangement of the feathers.
One final tricky note is that the Spotted has a close relative, Common Sandpiper, common in the Old World and straying into western Alaska. It is extremely similar to Spotted Sandpiper in behavior and patterned very much like it but without the spots. At a glance it seems identical, but with a closer look it shows a longer tail, usually a duller bill and legs, and a wider white wing-stripe in flight. It gives us one more reason to study the Spotty at every opportunity, so we'll know the Common Sandpiper if we happen to see one.
What to look for
Shape. For a sandpiper, relatively short-legged, long-tailed, round-headed, and straight-billed.
Face pattern. Pale brown face with darker eye-line and crown. Narrow, broken, white eye-ring.
Underparts. In non-breeding plumages, a pale brown patch at side of chest sets off a conspicuous white mark in front of wing.
Upperparts. In non-breeding plumage, back and scapulars relatively plain warm brown, wing coverts with some barring (more obvious on juveniles).
Posture and behavior. Usually fairly horizontal stance, with almost constant up-and-down bobbing of the hindquarters.
Among birds that walk along the water's edge, several bob their tails or "teeter" their hindquarters in a constant and conspicuous way. They include not only the sandpipers mentioned here but also birds such as waterthrushes, Palm Warbler, and American Pipit. It's hard to see the advantage of the behavior, since it makes the birds more conspicuous and presumably more vulnerable to predators. Scientists have suggested that the action evolved as a way of signaling to other members of the same species, especially close to rushing water, where sound might not carry. For solitary birds like Spotted Sandpipers and waterthrushes, silent signaling might help to avoid conflict by keeping individuals well spaced out.
Because male and female Spotted Sandpipers are so similar, it was not until about 1970 that researchers discovered their roles in raising young. Females are dominant, and one female may have up to four mates, laying a clutch of eggs to be incubated primarily by each of her "husbands." In some situations, females have only one mate, but even then the male does a major part of the incubation and caring for the young. This kind of role reversal has long been recognized in phalaropes. The Spotted is an extreme case among typical sandpipers, but there are several others in which the males do most of the tending of the young.