Bird of the Month - Sept 2005
Stilt Sandpiper
Micropalama himantopus
Great numbers of shorebirds migrate southward from far-northern breeding areas beginning in late June and continuing through late fall. This movement takes hundreds of thousands of shorebirds through California, where they rest and refuel in wetlands, on mudflats, and at shorelines. By proportion, most of these are the common and familiar species such as Western and Least Sandpipers, Dunlin, Sanderlings, Marbled Godwits, Willets, the dowitchers and yellowlegs, the plovers, and others. But among these throngs may occasionally appear an outrider, an oddball: a shorebird off the beaten track for most of its kind. The period from late July into early October is a good time to search particularly for the Stilt Sandpiper (Micropalama himantopus). Nearly 100 of these birds have been reported in northwestern California, and in 28 years since 1969 (Harris 2005).
Stilt Sandpipers are medium-small shorebirds, known by their slender proportions, long legs, and a rather long bill that is drooped at the tip. In alternate (breeding) plumage, one would not readily mistake an adult with its finely barred underparts and orange-chestnut cap and cheeks. However, juveniles and basic-plumaged adults can create confusion for less-experienced birders, as they are similar in many respects to several other species.
These waders breed on dry tundra above treeline in the central Canadian Arctic and in northern Alaska. Their route to and from the main wintering grounds in southern South America takes most of them across the eastern half of Canada and the U.S. Over nearly the entire West they are typically quite rare. In some years, single birds and very small flocks are detected at prime shorebird gathering sites such as lakeshores and sheltered mudflats.
Stilt Sandpipers feed by inserting the bill in soft or fluid mud and repeatedly plunging it up and down, as if sewing. It is likely that worms, tiny mollusks, and other small invertebrates form their diet while the birds visit our area. Because they share their need for soft mud and very shallow water with Long-billed and Short-billed Dowitchers and both species of yellowlegs, they are frequently seen in the company of flocks of those species. Their similarity to dowitchers in size, shape, coloration, and foraging style often causes Stilt Sandpipers to be nearly overlooked when a single bird is present amid a flock of dowitchers or other small shorebirds that probe when they feed.
While the sight of an alternate-plumaged Stilt Sandpiper in spring or summer is truly exceptional in the Redwood Region, any shorebird enthusiast who carefully works through the early fall flocks with an eye for an odd individual has a reasonable chance of eventually finding one of these birds in its subtle juvenile plumage. Watch for a nearly dowitcher-sized shorebird with comparatively longer legs, white-edged shoulder feathers, and a shorter bill that is distinctly drooped near the tip. Rather than having white extending well up the lower back, as in the dowitchers, the Stilt Sandpiper has a more restricted white rump and grayish tail.