Our extraordinary wrybill
By Cushla McGaughey
Like the more common Banded Dotterel, the Wrybill belongs to the Plover Family, but it is the world’s only bird with its bill curved to one side.
Seen from the front, the slender bill curves to the right. From the side it is spoon-shaped. It’s used with a sideways movement to sieve tiny creatures from the water or else to probe in the sand or mud and under stones. The tiny bills of newly-hatched chicks already have the distinctive sideways curve.
Grey upper and white underparts provide the Wrybill with effective camouflage on northern mudflats and shellbanks.
In breeding plumage, however, both male and female develop a dark band across the chest, the better to merge with the pattern of sunlight and shadow on their bare, stony breeding grounds. Males also gain a thin black edging to the white forehead.
Wrybills are about the size of a starling. Yet they fly 1,400 km each way between their winter feeding grounds in the North Island and their South Island breeding grounds. They have a more restricted breeding range than any other riverbed nester except the Black Stilt.
They nest only on the braided riverbeds of Canterbury and Otago. They do however use the Waikanae Estuary as a stopover on their way north or south.
Once they reach their southern breeding ground the flocks disperse into pairs. They need to establish separate territories, several hundred metres apart, on bare riverbed with clear visibility. The nest is just a scrape in the shingle between larger stones, where the two stone-coloured eggs are perfectly camouflaged. The chicks soon learn to feed themselves, guarded by their parents.
But with reduced nesting sites and increasing predators, fewer than 5,000 wrybills now remain.
Among the world’s remarkable and relatively rare braided river systems, New Zealand’s braided riverbeds stand out with the diversity of species they support. These are hostile, open wastelands, subject to winter snowfalls, spring floods, summer gales and scorching sun. Even so, our braided rivers are home to a unique community of plants and wildlife that has evolved over millions of years.
But this system is under threat as introduced willow and lupin lock the rivers into their beds. Encroaching vegetation prevents the spread of multiple channels. As a result, the open areas needed for nest sites are reduced, while cover for predators is increased.
Damming for power generation and taking water for irrigation also reduces the amount and quality of braided river habitat. Normal flooding scours the riverbeds clear: artificially reduced water flow allows vegetation and predators to multiply more rapidly.
Endangered species such as the wrybill continue to decline.