Variable Oystercatcher (Haematopus unicolor) at Frasers Beach
Maori names: Torea (Black phase, Toreapango)
Length: 48-49 cm
Distribution: Coastal around North, South and Stewart Islands. Black phase birds more common in the south and the only type on Stewart Island.
Food: Various bivalves, marine creatures. Worms.
Voice: Rippling ‚kervee.‘ High-pitched ‚tueep‘.
Breeding: Coastally. Sand-dunes and rocky shores. Simple scrape with two or three buff coloured eggs, spotted dark brown. Incubated by both adults for four weeks. Chicks fly at six weeks. Territorial all year. Non-breeders and young form small flocks.
As its name implies the Variable Oystercatcher has three plumage phases; pied, black and smudgy. Pied birds are similar to South Island Pied Oystercatchers but always lack the white marking around the top of the wing. Entirely black birds are seen more commonly in the South Island and black only on Stewart Island. Smudgy birds have varying amounts of black and white on their underparts. All are slightly bigger than the South Island Pied birds and are strictly coastal, nesting on most suitable shores around all three main islands and many off-shore islets. Pairs remain together for life and may be encountered on the same piece of coastline summer and winter. A musical rippling ‚kervee‘ heard during September indicates courtship is underway and the first eggs are laid between October and December. Variable Oystercatchers tend to be late nesters and second clutches or replacement nests may be found as late as February long after the South Island Pied Oystercatchers have completed activities and headed north. Two or three buff coloured eggs speckled dark brown are laid in a scrape in the sand or stones sometimes near driftwood or between sand dune vegetation. Often the scrape is unlined but occasionally a few stones, shells or adjacent sticks are moved in during incubation. Both adults share incubation duties which take nearly four weeks.
Those birds whose nests coincide with the peak holiday period have to contend with dune buggies, trail bikes and various off-road vehicles. Many nests are lost or deserted. The cryptic colouration of the chicks enables them to escape detection and dogs and other intruders are attacked but life is difficult for Variable Oystercatchers at Christmas time.
In six weeks young are flying. A few disperse hundreds of kilometres but usually small flocks of juveniles and non-breeders gather in suitable estuaries for the winter, while mature pairs remain territorial all year. Some Variable Oystercatchers join flocks of South Island Pied Oystercatchers.
Various bivalves are eaten and sand and estuary mud probed for a variety of marine creatures. Some take worms in coastal paddocks.