Variable Oystercatcher

Identificazione

"Variable" refers to the frontal plumage, which ranges from pied through mottled to all black. They are polymorphic meaning they have different genetic variants. These color differences are attributed to the latitude of the habitat, where the northernmost oystercatchers have significantly more white on their bodies than those of southern origin. All Stewart Island variable oystercatchers are black. They have pink legs, an orange eye ring and orange-red beaks. Similar to a needle in shape, the bill is thin and long, and darkens to a deep red color during the breeding season. Males are around 678 grams and females slightly larger at around 724 grams. Length of individuals range from 42 to 47 cm from beak to tail and have a short, sturdy body with a thick neck.<p>Variables can be identified as they are slightly larger than the South Island pied oystercatcher (SIPO are around 550 grams). Occasionally completely black, but if they are pied (black and white) they can be easily confused with SIPO. The variable species has less definition between the black and the white area, as well as a mottled band on the leading edges of the underwing. Variables also have a smaller white rump patch which is only a band across the base of the tail rather than a wide wedge shape reaching up to the middle of the back as in the SIPO. When mottled they are sometimes called "smudgies". While both sexes have the same plumage colorations and appear visually similar, there is some body dimorphism and female oystercatchers tend to be slightly larger in size.

Tassonomia

Genere: Haematopus; famiglia: Haematopodidae; ordine: Charadriiformes.

Nome scientifico

Haematopus unicolor

Autorità

Forster, JR, 1844

Ordine

Caradriformi

Famiglia

Haematopodidi

Genere

Haematopus

Areale e habitat

Haematopus unicolor is endemic to New Zealand. The species has likely remained endemic due to its sedentary lifestyle and lack of migration, keeping all populations within the same island habitat. They are often seen in pairs on the coast all around New Zealand. Their distribution around New Zealand is around most of the North, South and Stewart Islands coastlines and some offshore islands with the exception of outlying islands off the west coast. While they occur in lower densities on the western coastlines they are concentrated in these areas; Northland, Coromandel Peninsula, Bay of Plenty, Greater Wellington, Nelson/Marlborough and Fiordland.<p>Their preferred habitat is a wide range of coastal habitat types varying depending on activity and habitat available. Haematopus unicolor is generally never found more than 30 km from the coast. Breeding and nesting occurs on sandy coasts, usually far from muddy harbours. Individuals have been known to congregate in short grassed paddocks and sometimes forage in pastures after rain however will generally remain around the coastal beaches, estuaries and shorelines. They prefer sandy coastal areas and avoid gravel beaches and boulder strewn areas. They nest on the shore between rocks or on sand dunes by making a scrape out of the sand or shingle, sometimes lined with some seaweed.

Migrazione

Specie stanziale

Comportamento

Comportamento migratorio: Specie stanziale.

Conservazione

Tendenza della popolazione: in aumento.

Tendenza della popolazione

in aumento