Story: Wading birds
Page 5 – Wrybills and shore plovers
Sporting a sideways turning bill, the endemic wrybill (Anarhynchus frontalis) or ngutuparore is one of New Zealand’s bird oddities – the only bird in the world with such a feature. It uses the bill like a hook to gather insect larvae and eggs from beneath stones, or as a spoon to scoop crustaceans from mud.
The small wrybill has a pale grey back and wings and a white front, with a black chest band during breeding. It measures 20 centimetres and weighs just 55 grams. It breeds in inland areas of the South Island during in spring and summer, then flies to North Island harbours until the end of winter. Its main stop-off is the Firth of Thames, winter home to 50–60% of the wrybill population. As the time of departure approaches, wrybills gather in large flocks and perform elaborate aerial ballets.
Wrybills frequent the inland shingle riverbeds of the eastern South Island. They nest from August to January, laying two camouflaged grey-blue speckled eggs among the river stones. They often lay a second clutch if the first fails, and can raise two broods if the first fledges early enough. Wrybills tend to use shingle ‘islands’ for safety from predators. Hydro-electricity and irrigation schemes have robbed them of these sites, introduced weeds such as lupins have crowded out nesting areas, and predators have taken a toll. Consequently the population has declined, with an estimated total of 5,000 in 2012. They live up to 16 years, and like most other native birds are a protected species.
New Zealand shore plover
Scientists on Captain James Cook’s second voyage to New Zealand in 1773 discovered shore plovers (Thinornis novaeseelandiae, tuturuatu) in Dusky Sound and Queen Charlotte Sound. Unwittingly these explorers sowed the seeds of the birds’ extinction on the mainland, as Norway rats came ashore from the ships and began devouring the easy prey. On the mainland the last shore plover was seen in 1871, but a population survived on Rangatira Island in the Chatham Islands.
Wrecked on a reef
In 1999, 21 shore plovers were discovered on storm-exposed Western Reef off Chatham Island, 100 kilometres from the other surviving population on Rangatira Island. Their DNA suggests that this separate group existed in isolation for at least 100 years since rats had wiped out the birds on Chatham Island. Within a few years of their discovery, this sea-swamped but rat-free retreat had lost its charm – the reef was taken over by seals. The sole surviving Western Reef shore plover, named Westy, was taken into captivity, from where his offspring have been released at several secure sites.
Unlike other shorebirds, the starling-sized shore plover nests under thick vegetation, enabling predators to approach unseen. Even on the distant Chatham Islands, 850 kilometres east, the surviving plovers were not safe. In the early 1900s, collectors depleted the population: ‘[T]he incredible number of specimens in museums both local and overseas proves how eagerly these beautiful little plovers were sought after and what a good price they would fetch.’ 1
Their habitat on Rangatira Island is salt meadow and rocky reefs, where they feed on molluscs and invertebrates. Two to three pale buff eggs are laid under cover from October to January, which females incubate more than males. Chicks fledge at 40–55 days. Breeding begins at two to three years of age, and they live up to 20 years.
This is a rare endemic species. Since the 1990s captive-bred birds have been released on islands around mainland New Zealand. The total wild population was fewer than 200 birds, including about 65 pairs, in early 2013; there were around 10 pairs in captivity.
The grating rattle of the spur-winged plover (Vanellus miles) or masked lapwing has become a familiar sound in open country since this Australian immigrant started breeding in Southland in 1932. It has a distinctive yellow face mask, black cap and vertical shoulder band, tan back and wings and white front. The wings have spurs. Fiercely defending their nests, these birds shriek at and dive-bomb harriers and magpies that fly nearby.
They have become established on the mainland and Stewart Islands, the Chathams and Kermadecs, and have been recorded on subantarctic islands as well. Common in farmland and coastal sites, they feed on earthworms, insects and molluscs. From June to October they lay one to four khaki, blotched eggs in a scrape on rough open ground. This abundant, self-introduced species is considered a pest around airports and lost its protected status in 2010.