This group gathers Birds subcategory members belonging to the wader branch of the order Charadriiformes, small to medium-sized birds that forage by probing or picking along mudflats, beaches and the margins of lakes and rivers rather than swimming or diving for their food. It spans the plovers and lapwings, which hunt largely by sight in short running bursts, the sandpipers, curlews, godwits, snipes and woodcocks, most of which probe soft mud or ground with a long, sensitive bill to find invertebrates hidden below the surface, the stilts and avocets, distinguished by extremely long legs or an upturned bill used to sweep through shallow water, the oystercatcher, whose stout bill is adapted to prise open shellfish, and the jacanas, whose enormously long toes spread a bird's weight across floating vegetation, letting it walk on lily pads. Many members of this group undertake some of the longest annual migrations of any animal, moving between breeding grounds in the far north and non-breeding grounds thousands of kilometers south.