Dunlin
Calidris alpina

Dunlins are the most common wader in the UK, mainly found wintering along coastlines, but also breeding in summer in higher areas in central and northern England, Wales and Scotland while being resident in Northern Ireland. They are often found in winter in mixed flockas with their close relative the Sanderling and other small waders. Dunlins often migrate south in winter to Spain, the Middle East, Africa and Asia fro their breeding grounds further north. Their diet is mainly invertebrates and crustaceans, which they probe in mud and sand for with their slightly curved beaks. As they are so common, they tend to be a reference species for identifying other waders, allowing for size and plumage comparisons to be made (Dunlins themselves are 17-21 cm in length). In winter they tend to be greyish-brown above and light grey underneath while in breeding plumage, they are streaked brown above and have black bellies which are slightly different between subspecies.
 

1: Fleet Nature Reserve, Chesil Beach, Dorset, 04/08/2013.