Featured Article Summary #194

The curlew sandpiper (Calidris ferruginea) is a small wading bird that migrates long distances. It breeds in bogs and coastal lowlands of the Siberian Arctic from June to August or September, then travels south to winter in Africa and along coasts of Oceania and southern Eurasia, using tidal mudflats and saltpans. The species changes its plumage as it matures: adults have a less striking non-breeding look, and a deep rusty-coloured breeding look, while first-year birds usually stay in their wintering area and do not breed. Courtship includes several behaviours such as a fake ground nest, aerial chasing with calls, and ground dancing by the male. Females typically lay one clutch of eggs around late June; the chicks hatch after about 20 days and fledge within 14–20 days. The bird is listed as vulnerable due to habitat loss from land development and invasive smooth cordgrass, along with reduced breeding success from climate change, though its estimated annual survival rate is about 75–80%. The curlew sandpiper was first described in 1763 by Erik Pontoppidan as Tringa ferrugineus, and in 1764 Morten Thrane Brünnich assigned it the name Tringa ferruginea; it was later moved to the genus Calidris. The genus name comes from an Ancient Greek term for grey waterside birds, while ferruginea comes from Latin for “iron rust,” referring to its rusty breeding colour. The species has no recognized subspecies and is closely related to the stilt sandpiper, with occasional rare hybridisation also recorded with several other sandpipers. The curlew sandpiper is a small shorebird about 18–23 cm long and weighing 44–117 g, with dark bill and feet. It has seasonal feather changes (moults) and a distinctive look in all plumages, including a large white patch on the rump and a white wing stripe in flight. Its non-breeding plumage is greyish above and white below, and it fully replaces all feathers in the post-breeding moult, while earlier moults mainly replace body feathers and some wing feathers. Differences in breeding plumage vary by sex, and young birds have their own moults after they hatch, with plumage becoming more adult-like as feathers wear and are replaced. In breeding plumage, the curlew sandpiper can look similar to the red knot because both have a reddish belly. The red knot is larger, with paler orange-buff underparts, shorter greenish legs, a stockier bill, and a spotted greyish rump. It can also be distinguished from the red phalarope since the curlew sandpiper lacks a black patch on the top of the head, a white face patch, a straight yellow beak, and fully brick-red underparts. Only males sing. Their song lasts 10–15 seconds and includes introductory notes, trilled doublets, a four-part phrase, and long whine calls, while both males and females make shorter calls. Key calls include an alarm whik repeated on the breeding grounds, a shrill chase twittering mostly by males during courtship, a chirrup flight call during takeoff, and a loud ascending whaay whaay whaay used by males to defend territory.