longer outer feathers start to grow. Migration starts in November with the earliest fledged birds. Adults follow in January–February when breeding is finished with the rest of the fledglings. Migration back to breeding sites in the South Island happens in August. The current population is around 5000 individuals. Diet and foraging Wrybills are usually found foraging around shallow channels and around the edges of pools on insect larvae, aquatic invertebrates and sometimes small fish. They have evolved in a very distinct way to thrive on braided river beds: their beak is slightly tilted towards the right at an angle of about 12–26 degrees which is speculated to help them get insect larvae and small invertebrates that take refuge under the crevices of rocks; however this has never been conclusively proven. Predators and threats Threats are higher during the breeding season when the birds are at their most vulnerable. Threats include predation, flooding during nesting time, habitat degradation and disturbance from vehicles along the river beds. Introduced mammalian predators such as ferrets, stoats, weasels and hedgehogs pose a significant threat to the survival of the remaining population. Wrybills have adapted to bird predators such as raptors, gulls and owls, since mammalian predators have only been a threat since the arrival of people. Their chicks and eggs blend in very well with the surrounding shingle, camouflaging them from the predators flying overhead. Since rabbits are the main diet of introduced mammalian predators, when rabbit numbers are low these predators search further for their food and prey upon the ground nesting birds on the braided rivers. Flooding can destroy nests and disturb whole nesting areas, and can affect the number of chicks to reach fledging. As wrybills prefer an open clear area of shingle on the river bed to nest, introduced plant species such as gorse (Ulex europaeus), willow (Salix spp.), broom (Cytisus scoparius) and lupin (Lupinus spp.), all threaten the wrybill's habitat as they spread over the landscape easily and quickly. Conservation status The wrybill is rated as vulnerable on the International Union for Conservation of Nature (IUCN)'s Red List of Threatened Species, The population declined during the 1800s as they were collected as museum specimens because of their strange bent bill. In 1940 they were protected and the population has increased from around 2000 birds to 5000 birds today. References External links BirdLife Species Factsheet. Wrybill, New Zealand Birds Online Endemic