Slightly larger than the Common Sandpiper at 22-25 cm length, its long
upcurved bil l
– somewhat reminiscent of an avocet's, but not as strongly curved –
makes it very distinctive. As the scientific specific name implies, this
wader has a grey back, face and breast in all plumages; a white
supercilium may appear more or less distinct. The belly is whitish and
the feet yellow; the bill has a yellowish base, with the rest being
black.
The call is a high whistle.
Among the Scolopacidae, Xenus is part of the shank-tattler-phalarope
clade and less closely related to the calidrid sandpipers. Based on the
degree of DNA sequence divergence and putative shank and phalarope
fossils from around the Oligocene/Miocene boundary some 23-22 million
years ago, the Terek Sandpiper presumably diverged from their relatives
in the Late Oligocene. Given the numerous basal fossils of the group
found in Eurasia it is likely that the Terek Sandpiper lineage
originated there, possibly by being isolated as the remains of the
Turgai Sea dried up, which happened just around this time.
Distribution and ecology
This bird breeds near water in the taiga from Finland through northern
Siberia to the Kolyma River, and migrate south in winter to tropical
coasts in east Africa, south Asia and Australia, usually preferring
muddy areas. It is a rare vagrant in western Europe, and particularly in
autumn it is sometimes seen passing through the Marianas on migration;
on Palau, further off its usual migration route, it is decidedly
uncommon on the other hand. Almost annually and apparently more and more
often in recent times, a few birds stray to Alaska and the Aleutian and
Pribilof Islands. Every few years, individual vagrants are recorded in
the Neotropics, where they arrive either as migrating birds from Africa,
or as North American strays accompanying local waders south for winter.
Such vagrants have been recorded as far south as Argentina.It feeds
in a distinctive and very active way, chasing insects and other mobile
prey, and sometimes then running to the water's edge to wash its catch.
It lays three or four eggs in a lined ground scrape. |
