its the smaller bird the rest are Lesser Yellowlegs
The Pectoral Sandpiper (Calidris melanotos) is a small, migratory wader that breeds in North America and Asia, wintering in South America and Oceania. It eats small invertebrates. Its nest, a hole scraped in the ground and with a thick lining, is deep enough to protect its four eggs from the cool breezes of its breeding grounds. The pectoral sandpiper is 21 cm long, with a wingspan of 46 cm.