Common Ringed Plover (Charadrius hiaticula) and Semipalmated Plover (Charadrius semipalmatus)
Some taxonomists believe that the common ringed and semipalmated plovers are not distinct species, but are simply subspecies. The only physical difference between them is that the semipalmated plover has webbing between all three toes, while the common ringed plover has webbing between only two. There is very little overlap in their ranges, a major reason why taxonomists argue they are just one species.
The common ringed plover and the semipalmated plover have simple plumage: plain white underparts, plain brown upper parts, black primary feathers, and a black ring around their necks. A breeding plover has a white patch on its forehead outlined in black, a white eye-stripe, yellow legs, and a yellow bill with a black tip. In the winter, the ploverís black neck-ring is brown and its whole bill is black. These are dumpy birds measuring 16-19 cm in length, a little smaller than a starling.
The semipalmated plover breeds across North America and the Arctic, while the ringed plover breeds only in the extreme northeast of Ellesmere and Baffin Islands, and in the European and Asian Arctic.The migrations of these two species, or subspecies, take them as far away as South America. Males migrate north each spring slightly before females, in order to stake out nesting territories.
Their preferred habitat is quite barren and dry, on stony plains and rocky valleys. This preference is odd, because these plovers are considered wading birds, and their non-breeding habitat is much wetter. In most years four eggs are laid and subsequently incubated by both parents for 23 days. The parents leave the young at the breeding grounds in early August to return south, and the young follow at the end of September. The young need this extra time to lay down enough fat deposits to make the migratory journey. Adults and young alike often stop at estuaries on their way south, for up to three weeks.
Common ringed and semipalmated plovers feed on insects, although aquatic invertebrates are their primary food outside of the breeding season.