The Wrybill Anarhynchus frontalis: a brief review of status, threats and work in progress ADRIAN C. RIEGEN '1 & JOHN E. DOWDING 2 •231 ForestHill Road, Waiatarua, Auckland 8, NewZealand, e-maih riegen @xtra.co. nz; 2p.o. BOX36-274, Merivale, Christchurch 8030, New Zealand, e-maih
[email protected]. nz Riegen,A.C. & Dowding, J.E. 2003. The Wrybill Anarhynchusfrontalis:a brief review of status,threats and work in progress.Wader Study Group Bull. 100: 20-24. The Wrybill is a threatenedplover endemic to New Zealandand unique in havinga bill curvedto the right.It is specializedfor breedingon bareshingle in thebraided riverbeds of Canterburyand Otago in the SouthIsland. After breeding,almost the entirepopulation migrates north and wintersin the harboursaround Auckland. The speciesis classifiedas Vulnerable. Based on countsof winteringflocks, the population currently appears to number4,500-5,000 individuals.However, countingproblems mean that trendsare difficult to determine. The mainthreats to theWrybill arebelieved to be predationon thebreeding grounds, degradation of breeding habitat,and floodingof nests.In a recentstudy in the MackenzieBasin, predation by introducedmammals (mainly stoats,cats and possibly ferrets) had a substantialimpact on Wrybill survivaland productivity. Prey- switchingby predatorsfollowing the introductionof rabbithaemorrhagic disease in 1997 probablyincreased predationrates on breedingwaders. A recentstudy of stoatsin the TasmanRiver showedthat 11% of stoat densexamined contained Wrybill remains.Breeding habitat is beinglost in somerivers and degraded in oth- ers,mainly by waterabstraction and flow manipulation,invasion of weeds,and human recreational use. Flood- ing causessome loss of nestsbut is alsobeneficial, keeping nesting areas weed-free. The breedingrange of the speciesappears to be contractingand fragmenting, with the bulk of the popula- tion now breedingin three large catchments.