The Variable Oystercatcher (Haematopus unicolor) is a species of wading bird in the Haematopodidae family. It is endemic to New Zealand. This bird is locally known as the “˜red bill’. Their breeding habitats are the North Island, South Island, Stewart Island, and Chatham Islands. Along with the SIPO (South Island Pied Oystercatcher), they are the only oystercatchers in New Zealand.
The name “˜Variable’ refers to their frontal plumage, which ranges from pied, to mottled, to all black. They are polymorphic (having different genetic variants). The blacker birds are more common in the south of their range. All Stewart Island specimens are black. The have pink legs, an orange eye ring and red beaks. Variables that are pied (black and white) can be easily confused with SIPO. One easy way to distinguish them from SIPO is that they 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. Mottled variables are sometimes called “˜smudgies’. Males weigh about 24 ounces and females are slightly larger at 25.5 ounces.
Variables are often seen in pairs all around coastal new Zealand. During the breeding season, the pair will defend their territory, sometimes aggressively. Once mated, pairs rarely separate. The nest is built on the shore between rocks or on sand dunes by making a scrape out of the sand or shingle, sometimes lined with seaweed. The female lays up to 5 eggs, although 2 to 3 is the norm. The eggs are stone colored with small brown patches. Incubation lasts 25 to 32 days. Chicks are born with cryptic plumage that camouflages them form predators. They can fly in about six weeks. Outside the breeding season they may be seen in or near flocks of SIPO. They may form small flocks of their own outside the breeding season. The lifespan of these birds is up to 27 years.
The diet of the Variable Oystercatcher consists of mollusks, crabs and marine worms. They sometimes will go inland in search of earthworms after heavy rains have come. They can open a shellfish by either hammering a hole in it or getting the bill between the two shells (of a bivalve) and twisting them apart.