Icons of Migration: Bar-tailed Godwit

Some Alaskan Bar-tailed Godwits (Limosa lapponica) have the longest non-stop flight of any migrating bird. According to some biologists, the birds stay airborne for almost one week, making a 6,800-mile beeline from wintering grounds in southeast Asia, Australia, and New Zealand to their breeding range in Alaska, Siberia and Scandinavia.

Some routes of satellite tagged Bar-tailed Godwits migrating north from New Zealand:

More on this species’ identification, ecology, and conservation below the fold.

Identification
Bar-tailed Godwit is easily identifiable as a godwit by its large size and large, upturned bill. In breeding plumage, males have rich chestnut-red heads and underparts, and dark wings and upperparts touched with small amounts of chestnut. Breeding females are less colorful than males, with some light chestnut coloring on the upper breast fading to white down below. Non-breeding birds are much drabber, with grayish-brown upperparts, gray streaking on the breast, and white underparts. In its limited North American breeding range, Bar-tailed Godwit is only likely to be confused with Hudsonian Godwit, which also breeds in western Alaska. Breeding male Hudsonian Godwit, however, does not have the rich chestnut-red coloration of Bar-tailed Godwit on its head, and has a prominent white eye-line. In flight, Bar-tailed Godwit lacks the white wingbar of Hudsonian Godwit.

Ecology
On its breeding grounds in Alaska, Bar-tailed Godwit nests on tundra hillsides with short shrubby growth and hummocky ground cover. Breeding birds will sometimes leave nesting habitat to feed at coastal lagoons located some distance away. During migration and on wintering grounds, Bar-tailed Godwit is found primarily on coastal mudflats, where it probes in exposed mud or shallow water for crustaceans, mollusks, insects, and annelid worms. In Alaska, birds feed heavily on aquatic insects, but will occasionally eat seeds and berries. Individuals do not reach sexual maturity until two years of age. Males perform elaborate courtship and territorial displays in which they call loudly and circle high above the tundra in flight. The nest is a shallow depression, lined with grass, moss, and lichens, placed on a raised hummock surrounded by grass. Clutch size is usually four eggs, and both sexes participate in incubation, which lasts about three weeks. A short time after hatching, chicks are led by both parents to marshy areas, where the young find all their own food. On migration, it is believed that Alaskan breeders fly long distances over the Pacific Ocean en route to Australia and New Zealand, rather than quickly crossing the North Pacific and then moving south along the Asian coastline.

Conservation
The U.S. Shorebird Conservation Plan lists Bar-tailed Godwit as a “Species of High Concern,” based on its low relative abundance, threats on non-breeding grounds, and restricted U.S. breeding distribution. The breeding population of Bar-tailed Godwit in North America is concentrated in a limited area along the coastal plain of western Alaska, placing it at higher risk to potential disturbance. While Bar-tailed Godwit is protected in the United States under the Migratory Bird Treaty Act, and is also protected on its wintering grounds in New Zealand and Australia, it is not protected on the migratory pathway along the eastern coast of Asia. If Alaskan Bar-tailed Godwits do follow the Asian coastline southward more than is believed, hunting in eastern China could have a serious negative impact on the North American population of this species.

References

• Gill RE, Piersma T, Hufford G, Servranckx R, Riegen A. Crossing the ultimate ecological barrier: Evidence for an 11,000km-long nonstop flight from Alaska to New Zealand and eastern Australia by bar-tailed godwits, The Condor 2005, 107(1): 1-20.
• Audubon Watchlist
• Wikipedia