Black-bellied Plover, Pluvialis squatarola
Black-bellied Plover, Pluvialis squatarola, Wintering Non-breeding Adult. Photograph taken with the rocky shoreline of the greater Bahía de los Ángeles area, Baja California, January 2019. Photograph courtesy of George Flicker, Bahía de los Ángeles. Identification courtesy of Mary & George Flicker, Bahía de los Ángeles.
The Black-bellied Plover, Pluvialis squatarola is a member of the Charadriidae Family of Plovers and Lapwings, which has sixty-eight members placed in ten genera, and is one of four global species of the Pluvialis Genus. They are also known as the Grey Plover and in Mexico as chorlo gris.
The Black-bellied Plover is a large plover, with a large head, thick neck and a large thick, short, bill that tapers to a blunt point. The sexes are similar in appearance. Their definite basic wintering plumage, present from September to February, have brownish gray to dark brown underparts with most feathers fringed with pale gray-brown, pale gray-brown forehead, supercilium and auricular areas, a white rump and uppertail coverts, underwing coverts that are uniformly gray-brown with white fringes and dark brown primaries and secondaries. Their breast and side vary from pure white to grayish, variably mottled brown. Their bills are black, their iris is dark brown, their legs and feet are a medium to dark gray and become black in breeding adults. They have long pointed wings that extend past the tail tip. They have relatively short legs and toes with a well-developed web between the base of the outer and middle toes and a smaller one between the middle and inner toes. They have a hallux (small hind toe) which is unique among the plovers.
In Mexico the Black-bellied Plover is a coastal bird that is normally found foraging over sandy and muddy flats during low tide periods. They have large eyes that allows them to forage nocturnally. Although generally a coastal bird, Black-bellied Plover also forages successfully in freshwater and upland habitats. They mainly consume bivalves, crustaceans, insects, invertebrates and polychaetes, and varies by location and substrate. They are subject to heavy predation by Glaucous Gulls, Herring Gulls and Jaegers but are known to attack intruders in groups. Their nests are subject to raids by Artic Fox, Falcons, Northern Harriers, and Owls. They roost in large flocks of up to 1,000 individuals on the upperparts of beaches, dunes, pastures, within salt marshes, and in mangrove trees. The Black-bellied Plover is wary and functions worldwide as a sentinel for mixed-species assemblages of shorebirds providing immediate alarm calls. As the largest and widest ranging marine plover they have served as a model for studies of other shore birds. They have life spans of thirteen years with high survival rates of their juveniles.
The Black-bellied Plover are long-distance high flight speed migrators that make annual spring and fall migrations. They summer and breed in the high Arctic and overwinter in both temperate and tropical climates. They breed in a narrow range and wintering in a wide range. Females winter farther south than males and juveniles farther south than adults. In Mexico they are found between October and February along the entire Atlantic and Pacific Coasts. Small populations are also found in the interior of the mainland, at elevations up to 3,700 m (12,100 feet) and on Clipperton Island.
The Black-bellied Plover might be confused with the American Golden Plover, Pluvialis dominica (lacks a hind toe, smaller in stature, lacks black axillaries) the only other Plover found in Mexico during the winter months.
From a conservation perspective the Black-bellied Plover is currently considered to be of Least Concern with stable, widely distributed populations. They were heavily pursued by hunters during the 19th and 20th centuries but resisted populations eradications. Their breeding grounds are far away from human civilization and thus of low risk to habitat alternation. Their wintering grounds, in some areas, have been lost to human coastal developments. They date to the Pleistocene Period, 2,580,000 to 11,700 years ago.