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The wrybill | ngutu pare (Anarhynchus frontalis) is a small plover endemic to New Zealand with a unique laterally curved bill. Apart from moult, much of its biology is well understood: adults breed from late August to January on the braided river systems in Canterbury and inland Otago on New Zealand’s South Island. From midsummer, late December and January, they migrate north to non-breeding areas in the northern part of the North Island, especially to the large tidal bays, east and west of Auckland, where they undergo primary moult from January to April. The Underhill- Zucchini moult model was used to estimate the mean start and completion dates of primary moult, which were 20 January and 3 April respectively. Adults thus commence primary moult soon after arrival on non-breeding grounds but complete moult around four months before southward migration to their breeding areas in August. They appear to avoid primary moult during winter. Second-year birds start primary moult in December, one month earlier than the adults, but finish at approximately the same time. Primary moult of the wrybill is compared with closely related species, and with other waders that breed on the South Island and migrate to North Island for the non-breeding season.