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. Researchis currentlybeing undertaken on longevity,survival to breedingage, and natal dispersal. Further data on theseaspects are requiredto assistin modelingtrends in the population.Nearly all of the recent demographicdata have beencollected in the MackenzieBasin, where the populationis almostcertainly in decline.There is reasonto believethat the datamay not be typical,and demographic data are requiredfrom otherparts of the breedingrange.

INTRODUCTION "scything"motion (Turbott 1970). Largely because of its unu- sual bill, the Wrybill is currentlyplaced in the monotypic The Wrybill Anarhynchusfrontalisis a smallgrey andwhite genusAnarhynchus (Turbott 1990). However, otherfeatures ploverunique in the bird world, beingthe only specieswith of the skull are typical of Charadrius (Burton 1972), and a laterally curvedbill. In breedingplumage, it showsslight Holdaway et al. (2001) have suggestedthat the Wrybill sexualdimorphism--males have a narrowblack frontalbar shouldbe placedin that genus. between the forehead and crown which the females lack After breeding,most of the population migratesto the (Marchant & Higgins 1993). large harbours of the Auckland region in North Island Wrybills are endemicto New Zealand,where they breed (Sibson1963), in particularthe ManukauHarbour and Firth only on braidedriver systemseast of the SouthernAlps be- of Thames,which togetherappear to supportabout 85% of tween 43 and 45øS (Marchant & Higgins 1993, Fig. 1). the population(Davies 1997, Sagaret al. 1999, Fig. 1). Indi- Braidedrivers are rare globally, but are characteristic of South vidual adultstend to be faithful to a winteringsite, but there Island, New Zealand. They developedduring glacial melt are no apparentlinks betweenbreeding and wintering areas when vastwater-flow carriedgravels into the valleys.They (Hay 1984) About 90% of birds leave the North Island har- consistof numerouslinked channelsspread across gravel- bours in August and migrate south. Some non-breeding filled floodplains,often several km wide. Wrybills appearto adults and first-year birds migrate south later (October- be well adaptedto breedingon thegreywacke shingle of these November)and a few (mostlyfirst-year birds) remain in the riverbeds;eggs and chicks are highly cryptic,and incubating northernharbours for the entire breedingseason (Marchant adultsare secretiveand well-camouflaged. The bill, the distal & Higgins 1993). third of which curvesto the right by 12-26ø (Hay 1984), is The breedingbiology of the specieswas studiedin detail usedon the riverbedsto probeunder stones for insects,par- by Hay (1984), andfurther information on breedingecology ticulafiy mayfly Deleatidiumspp. larvae (Pierce 1979). On was provided by Hughey (1985a). Wrybills normally first the mudflatsof northernharbours it is effectivelyused in a breed at two years,but breedingin the first year has been

* Correspondingauthor • Bufietin100April2003 20 Riegen & Dowding: Wrybill Anarhynchus frontalis 21 recorded(Dowding et al. 1999). They nearly alwaysbreed NEW ZEALAND as monogamouspairs in well-spacedterritories (Hay 1984), and the laying seasonextends from late Augustto Decem- ber. Replacementclutches are laid after loss and double- brooding occursregularly - the number of pairs double- • .•Auckland broodingvaried from 11 to 32% during three consecutive seasonson the upperRakaia River (Hay 1984). Birds begin leavingthe breeding grounds from late December,and nearly all have left by early February. Since 1979, the New Zealand Wader Study Group (NZWSG) has metal-bandedmore than 5,000 Wrybills on the winteringgrounds, studying longevity, recruitment and movements,particularly within the Aucklandregion. Since 1987, a colour-bandingstudy has been in progress,primar- ily in theTasman and Tekapo Rivers of theMackenzie Basin, central South Island. In thispaper, we briefly review currentknowledge of the SOUTHISL7 speciesand the threatsit faces,report on somerecent find- ings andresearch in progress,and identify areasof research TasmanR._ /'• • AshleyR, that would assistwith conservationof the Wrybill. McKenzie ' •RaikaiaR. Waitaki R. STATUS AND POPULATION

Status •' Keysites mentioned intext The Wrybill (see Fig. 2) is classified as "Vulnerable" by BirdLife International (2000), and is consideredthreatened Fig. 1. Locationmap showingthe main Wrybill breedingsites on by habitatloss, invasive species, native speciesand human the rivers of South Island, New Zealand, and the main wintering disturbance.In New Zealand,the Departmentof Conserva- sites around Auckland on North Island. tion hasrecently ranked the speciesas "NationallyVulner- able";the two rankingsare equivalent(Molloy et al. 2001).

Population size whena countof 4,143 birdsrepresented an apparentdecline of 19% in sevenyears (Riegen & Dowding 2001). Because Duringbreeding, the populationis widely andthinly spread this was of considerableconcern, a further count was under- on SouthIsland riverbeds. Many areasare difficult of access, takenin May 2002. This includedflocks that together tradi- andthe speciesis highly crypticin thishabitat. An accurate tionallyheld about95% of the populationand resulted in a censusunder these conditions is virtuallyimpossible. Popu- total of 4,650 andestimated population of about4,900. lation size hastherefore been estimated by countingwinter- Someof thevariation apparent in thesecounts may be due ing flocks in the North Island harbours. to annualdifferences in productivity,but sightingsof colour- There are few quantitativedata from before 1940; counts bandedbirds in the Aucklandflocks also suggest that there from the 1950ssuggested a populationof about5,000 birds may be considerablymore local movementbetween roost (Sibson1963). Countsof Wrybills (and otherwaders) have sites in winter than previously thought (J.E. Dowding, been undertaken in the Manukau Harbour and Firth of unpubl.data). Auckland' s locationon a narrowisthmus, with Thameseach winter since the early 1960s(Veitch & Habraken harbourson both sides,may also createproblems - high 1999).Combined totals for the two harboursaveraged 3,770 water differs by aboutthree hourson the two coastsand at duringthe 29 years,1962-1990. On thebasis that 85% of the least two flocks are known to commute between the har- populationis foundon theseharbours (Sagar et al. 1999),the bours,feeding on the falling tide on both (Dowding2001). nationalpopulation averaged about 4,500 over thoseyears. The Ornithological Society of New Zealand (OSNZ) also Population trends conducted national wader counts between 1983 and 1994. Theseshowed a winteringpopulation ranging from a mini- Becauseof the difficulty in obtainingaccurate estimates of mum of 2,807 in 1987 to a maximum of 4,418 in 1988. Based populationsize from the winter counts,it is clearly alsodif- on thesecounts the populationwas estimatedat 3880 (Sagar ficult to detect overall trends.Veitch & Habraken (1999) et al. 1999). notedthat the Wrybill may be declining,but high variabil- Becausethese estimates varied considerably,a national ity in the countsthey analysedfor Manukau/Firthof Thames Wrybill censuswas undertaken in May 1994 (Riegen1994). (a minimum of 2,120 in 1963 and a maximum of 7,807 in Winter Wrybill flocksare normally very denseand counting 1969) obscuredany clear trend. canbe difficult.Flocks containing >300 birdswere therefore Neverthelessthese counts (and the nationalWrybill cen- photographedand countedfrom the photos. The census suses)do suggesta changein winter-siteallegiance in recent appearedto have had goodcoverage and resultedin a total years,with numbersfalling in the Firth of Thamesand ris- count of 5,111 birds, of which 83% were in the Manukau ing in the ManukauHarbour. The reasonfor this is not yet Harbour and Firth of Thames (Davies 1997). clear.There still appearsto be abundantfeeding habitat in the A secondnational census was undertakenin May 2001, Firth of Thames(wintering Wrybills favourareas of softwet

Buffetin 100 April 2003 22 Wader Study Group Bulletin

Fig. 2. The Wrybill Anarhynchusfrontalis. mud for foraging). However, one obviouschange has been predators(Dowding & Murphy 2001). In particular, the the spreadof mangrovesAvicennia marina resinifera(Veitch Wrybill hasa loweredreproductive rate; it laysonly two eggs 1978), which areincreasingly covering shell banks tradition- (the modal clutch for most Charadriusplovers is three or ally usedas high waterroosts by Wrybills and otherwaders. four),incubation and fledging times are extended, and repro- Relatively little attentionhas been given to the threats ductivematurity is delayed(two yearsinstead of one). It is facingthe Wrybill on its winteringgrounds. As notedabove, ground-nestingand may alsobe behaviourallynaive towards there has been some loss of traditional roost sites in the Firth mammalianpredators--incubating birds perform distraction of Thames,but nothingis known of the possibleimpacts of displaysvery closeto humanintruders near the nest, and will suchhabitat degradation on Wrybills at the populationlevel often returnto the nestwith a persononly 3-4 m away. in the longer term. However, Aucklandis the most densely In his 1975-77 study in the upper Rakaia River, Hay populatedpart of the country,and there will inevitably be (1984) found little impactof predationon nestor chick sur- growing human pressureon local harboursfrom develop- vival. Over the three seasons,productivity averaged 0.79 ment, recreationaluse, and pollution from agriculturaland chicksfledged per pair per season,and annual adult survival industrialrun-off. Mortality of Wrybillsfrom collisionswith averaged0.83 (Hay 1984). In contrast,the resultsof a study power-linesand aircraft strikeshas been recorded.While in the Tasmanand Tekapo Rivers (MackenzieBasin) from further work on these topics is clearly desirable, current 1997-2000 suggestedthat predation did have an impact knowledgesuggests that the importantand immediate threats (Dowding & Murphy 2001). Productivity was much lower to the speciesare on the breedinggrounds. than in Hay's study. Adult survival was similar overall at 0.80, but there was a difference between areaswith and with- THREATS TO THE BREEDING POPULATION out predatorcontrol, with adult survivalsignificantly lower in the absenceof control.Preliminary modelling of thesedata The main threatsto Wrybills on the breedinggrounds cur- indicatesthat the Mackenzie Basin Wrybill populationmust rently appearto be predation,degradation of riverbedhabi- be in decline(E.C. Murphy & J.E. Dowding, unpubl.data). tat, and flooding. The relative importanceof thesefactors A recentradio-telemetry study of stoatsMustela erminea in almostcertainly varies between and within rivers (Dowding the TasmanRiver, MackenzieBasin, has shown that they are & Murphy 2001). an importantpredator of Wrybills and otherwaders. Of 128 stoatdens that containedidentifiable prey remains,no fewer Predation than 14 (11%) containedWrybill remains (J.E. Dowding, E.C. Murphy& M.J. Elliott, unpubl.data). One of thesedens, New Zealand' s endemic birds evolved in the absence of ter- usedby a femalestoat, contained the remains of at leastseven restrialmammals, and many of them (includingthe Wrybill) Wrybills. display featuresthat render them vulnerableto introduced One factor that may accountfor the differencesbetween

Bulletin 100 April 2003 Riegen & Dowding: Wrybill Anarhynchus frontalis 23 the Mackenzie Basin studyand that of Hay (1984) is an in- Flooding direct effect of rabbit Oryctolagus cuniculus control (see Dowding & Murphy 2001). The arrival of rabbit haem- The larger braided rivers are snow-fed, and peak flows oc- orrhagicdisease (RHD) in New Zealandin 1997 appearsto cur in springand early summerduring breeding (e.g. Hughey have inducedprey-switching by predatorsin the Mackenzie 1985a). Flooding causesthe loss of many Wrybill nestsin Basin,which was estimatedto hold at least 15% of breeding someyears, and was the major causeof breedingfailure in Wrybill population(Maloney et al. 1997).With theirprimary Hay's (1984) study. However, the speciesappears to be prey (rabbits) much reduced,predators switched to eating adaptedto flooding,with somepairs re-laying very quickly more birds,lizards and invertebrates(Murphy et al. submit- afterloss (Hay 1984). Floodingalso has a benefit- the scour- ted). ing action of floods is importantin maintainingweed-free In otherparts of the Wrybill's breedingrange, RHD has nestingareas (Hughey 1985b). While flooding is a natural been less successfulat reducing rabbit densities.Further phenomenon,it shouldbe rememberedthat lossesto flood- insightsinto the impactof predationon the populationas a ing arenow additionalto lossesto predationand other causes. whole is now likely to comefrom data on survivaland pro- ductivity of birds outside the Mackenzie Basin, in areas Changes in breeding range where the potentialimpacts of prey-switchingon Wrybills havenot beenstudied. With the MackenzieBasin population The breedingrange of Wrybills has contractedsouthwards in decline, thesedata are now urgently needed. in the past century,with the speciesno longer breedingin Marlborough or northern Canterbury (see Dowding & Habitat degradation Murphy 2001). There may have beensome expansion to the south,but overall the breedingrange appearsto have con- Wrybillsrequire large, bare areas of shingleon whichto nest, tracted.The northern-mostbreeding site is now the Ashley with shallowriffles andbackwaters nearby in which to feed River, but this populationis small, with six pairsin the early (Hughey 1985a). Suchareas are part of a dynamic,unstable 1980s (Hughey 1985a) and only three pairs in 2002 (J.E. systemsubject to regularflooding and to which the Wrybill Dowding, unpubl. data). Although Wrybills have been re- is highly adapted(Robertson et al. 1984). Braidedrivers are cordedbreeding on manyrivers in the past30 years(e.g. Hay subjectto a wide range of impacts,many of them human- 1984, Marchant& Higgins 1993), anecdotalevidence sug- induced, that can cause loss of these features. geststhat most of the smaller,narrower rivers now havevery Hydro-electricschemes, notably in the MackenzieBasin, few or no Wrybills, possiblybecause their flows have been have flooded some Wrybill breedinghabitat permanently reducedand they are now extensivelyinvaded by weeds.It (e.g. part of the TasmanRiver floodedby Lake Pukaki), and appearslikely that the breedingrange of the speciesis be- removedwater almostentirely from otherareas (e.g. Pukaki comingincreasingly reduced and fragmented, with the large River). Releases of water may also change flow regimes majority of the populationnow confinedto three areas- the suddenlyand unnaturally. rivers of the upper Waitaki (Mackenzie) Basin, the upper Water abstractionfor irrigationon the CanterburyPlains Rangitataand its tributaries,and the Rakaia and its tributar- reducesthe flow ratesof many rivers, and may even cause ies.This distributionwas already emerging during the 1970s total drying of some reaches(Cromarty & Scott 1996). At (Bull et al. 1985), when the Rakaia appearedto be the only lower flow rates, predatorshave easier accessto islands, river with a sizableWrybill populationon its lower reaches. gravel areasbecome less dynamic and weed growth is en- The OSNZ atlasproject currently under way will providea couraged.Water quality has alsobeen affected,mainly by much-neededupdate on the breeding distribution of the agriculturaldischarge. Most of Canterbury'sbraided rivers Wrybill. arenow highly modifiedby exoticweeds, notably gorse Ulex europaeus, Spanish broom Cytisus scoparium, willows RESEARCH IN PROGRESS (mainly Salix fragilis) and tree lupin Lupinus arborea (Cromarty & Scott 1996). Weed growth reducesnesting Since1979, the NZWSG hasbanded 5,014 Wrybills andre- habitat,stabilizes islands and deepens channels, and provides trapped1,245 of them.Davies (1997) recordedthe minimum cover for mammalian predators. agesof birds caughtduring 1987-1996 and found the old- Recreationaluse of riverbedsby peoplemay also reduce est to be at least 16 years.Since 1996, six birds are known habitat quality in a numberof ways. People, vehiclesand to have reached a minimum of 18 years (A.C. Riegen, dogsmay crushnests or small chicksand disturbbreeding unpubl.data). Furtheranalysis of thesedata is in progress. and foragingbirds; prolonged disturbance (e.g. by picnick- Data are being gatheredon survivalfrom fledgingto one ers or anglers)may result in temporaryabandonment of in- year of age, using birds colour-bandedas juveniles in the cubationand deathof the eggsby chilling or over-heating. Mackenzie Basin; preliminary resultssuggest that survival The washfrom jet-boats may swamplow-lying nests or small is not high, at about0.45-0.50 (J.E. Dowding,E.C. Murphy chicksforaging at the water's edge. & M.J. Elliott, unpubl.data). This is consistentwith the sug- While the impactof habitatdegradation on total popula- gestionof Davies (1997), basedon the proportionof juve- tion size is not clear, there can be little doubt that it is caus- nilesin winterflocks, that post-fledging survival may be low. ing changesin breedingdistribution. Growth of weeds,water Further data are required to assistwith the modelling of abstraction,the constructionof flood-protectionworks and populationtrends. disturbancefrom recreationaluse have had their greatest Preliminaryresults suggest that fidelity to natalsite is high impactson the lower sectionsof Canterbury'slarger rivers in Wrybills, with most young birds returningto breed on (Cromarty& Scott1996). Outsidethe MackenzieBasin, high their natal river and within about 10 km of their natal site densitiesof Wrybills are probablynow presentonly on the (J.E. Dowding, M.J. Elliott & E.C. Murphy, unpubl.data). upperreaches of the two or threelargest river systems. Again, further data are required,but if this finding is con-

Bulletin 100 April 2003 24 Wader Study Group Bulletin firmed there are obviousconservation implications - once Cromarty, P. & Scott,D.A. 1996.A Directoryof Wetlandsin New Zea- the speciesis lost from a river (or possiblyfrom onepart of land. Departmentof Conservation,Wellington. a larger river), it is lesslikely to re-colonisenaturally. This Davies,S.J. 1997.Population structure, morphometrics, moult, migration, and winteringof the Wrybill (Anarhynchusfrontalis).Notornis 44: 1- processwould inevitably lead to contractionand fragment- 14. ation of the breedingrange. Dowding, J.E. 2001. Numbers,distribution and movementpatterns of shorebirdsusing the southernarm of the upper WaitemataHarbour. RECOMMENDATIONS FOR FURTHER STUDY Unpublishedreport to AucklandConservancy, Department of Conser- vation. If the long-termconservation management of the Wrybill is Dowding,J.E. & Murphy, E.C. 2001. The impactof predationby intro- duced mammals on endemic shorebirds in New Zealand: a conserva- to be basedon a soundfooting, furtherresearch is required tion perspective.Biol. Conserv. 99: 47-64. on both the breedingand wintering grounds. Estimating the Dowding, J.E., Murphy, E.C., Elliott, M. & Duirs, R. 1999. A record size of the Wrybill populationaccurately and reproducibly of a Wrybill (Anarhynchusfrontalis) breeding at one year old. from winter flockshas proved difficult, but it currentlyap- Notornis 46: 240-241. pearsto be in the range4,500-5,000 individuals.The abso- Hay, J.R. 1984. The behaviouralecology of the Wrybill plover Ana- lute numberof individualsis lessimportant than the trendin rhynchusfrontalis.Unpubl. Ph.D. thesis,Univ. Auckland. the population.However, without an accurateand reproduc- Holdaway, R.N., Worthy, T.H. & Tennyson,A.J.D. 2001. A working list of breedingbird speciesof the New Zealandregion at first human ible countingprotocol, the determinationof trendsfrom win- contact.New Zealand Journal of Zoology 28:119-187. ter countsis not possible.Counts of the main winter flocks Hughey, K.F.D. 1985a.Hydrological factors influencing the ecologyof shouldcontinue annually; further studyof local movements riverbedbreeding birds on the plains' reachesof Canterbury'sbraided aroundAuckland (usingcolour-banded birds) may assistin rivers. UnpublishedPh.D. thesis,Univ. of Canterbury,Christchurch. refining surveyprocedures. Hughey, K.F.D. 1985b.The relationshipbetween riverbed flooding and non-breeding wrybills on northern feeding grounds in summer. Modelling demographicdata to determinetrends might Notornis 32: 42-50. proveinvaluable, but, as notedabove, there is reasonto be- Maloney, R.F., Rebergen, A.L., Nilsson, R.J. & Wells, N.J. 1997. Bird lieve that survivaland productivityin the MackenzieBasin densityand diversityin braidedriver bedsin the Upper Waitaki Basin, population- from which most recent data have been col- South Island, New Zealand. Notornis 44: 219-232. lected - may not be representativeof the population as a Marchant, S. & Higgins, P.J. (eds), 1993. Handbookof Australian,New whole. Detailed data shouldtherefore be collected elsewhere, Zealand & Antarctic Birds, Vol. 2 Raptors to Lapwings. Oxford Uni- preferablyin both the Rakaia and RangitataRivers, which versity Press,Melbourne. Molloy, J., Bell, B.D., Clout, M.N., de Lange, P., Gibbs, G., Given, D., togetherprobably now hold a largemajority of the breeding Norton, D., Smith, N. & Stephens, T. 2001. Classifyingspecies populationoutside the Mackenzie Basin. Further data are accordingto threat of extinction:a systemfor New Zealand.Depart- alsorequired on survivalfrom fledgingto breedingage, and ment of Conservation,Wellington. on natal-sitefidelity and its implications. Murphy, E.C., Keedwell, R.J., Brown, K.P. & Westbrooke, I. (Submit- ted). Diet of predatorsin the Mackenzie Basin after the release of rabbit haemorrhagicdisease (RHD). Wildlife Research. ACKNOWLEDGEMENTS Pierce, R.J. 1979. Foodsand feedingof the Wrybill (Anarhynchusfron- talis) on its riverbedbreeding grounds. Notornis 26: 1-21. We are grateful to the large number of people who have Riegen,A.C. 1994.National Wrybill Census- 29 May 1994. OSNZNews helped with national and local wader and Wrybill counts 72: 2-3. over the past 42 years.We also thank thosewho have been Riegen, A.C. & Dowding, J.E. 2001. Wrybill census2001. SouthernBird involved with bandingWrybills throughthe NZWSG, and 7:7. the many people who have reported sightingsof colour- Robertson, C.J.R., Law, E., de Hamel, R.J.B., Wakelin, D.J. & bandedbirds. Fundingfor part of the colour-bandingstudy Courtney, S.P. 1984. Habitat requirementsof wetland birds in the lower Waitaki River catchment, New Zealand, vol. 1. New Zealand in the Mackenzie Basin and for stoat research in the Tasman Wildlife Service Occasional Publication No. 6. Department of Inter- River was provided by the Department of Conservation nal Affairs, Wellington. (Science & Research Unit); particular thanks to Elaine Sagar, P., Shankar, U. & Brown, S. 1999. Distributionand numbersof Murphy and Mike Elliott for much help with both these waders in New Zealand, 1983-1994. Notornis 46: 1-43. projects.We also thank Dick Veitch for commentson an Sibson,R.B. 1963.A populationstudy of the wry-billedplover (Anarhyn- earlier draft of our manuscript. chusfrontalis). Notornis 10: 146-153. Turbott, E.G. 1970. The Wrybill: a feedingadaptation. Notornis 17: 25- 27. REFERENCES Turbott, E.G. (convener)1990. Checklistof the Birds of New Zealand and the Ross Dependency,Antarctica, 3rd edn. Random Century, BirdLife International. 2000. Threatened Birds of the World. Lynx Auckland. Edicions,Barcelona & BirdLife International,Cambridge. Veitch, C.R. 1978. Wadersof the ManukauHarbour and Firth of Thames. Bull, P.C., Gaze, P.D. & Robertson, C.J.R. 1985. The Atlas of Bird Notornis 25: 1-24. Distributionin New Zealand.Ornithological Society of New Zealand, Veitch, C.R. & Habraken, A.M. 1999. Wadersof the ManukauHarbour Wellington. and Firth of Thames. Notornis 46: 45-70. Burton, P.J.K. 1972. Someanatomical notes on the Wrybill. Notornis19: 26-32.

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