Though superficially similar to a few closely-related wading birds, knot are distinctive when seen well. They arrive from the arctic in late summer, still in breeding plumage. No other shorebird has the copper colour of the belly of a breeding plumage knot, though the much scarcer curlew sandpiper is an intense brick red. The tight flocks of thousands of these birds which flash their copper bellies over the shore of the Wash at high tide in August are an unforgettable sight. In winter the knot is a flat pale grey, delicately barred grey and white below. At all times of year the knot is bigger and more pot-bellied than dunlin and sanderling and its bill and legs are black.