Woodcock Research Group (IWRB)

MONICA SHORTEN

East Gate, Old Castle Road, Salisbury, WiltshireSP1 3SF, UK

Citation: Shorten, M. 1975. Woodcock Research Group (IWRB). Wader Study Group Bull. 15: 12.

The exasperatingWoodcock Scolopax rusticola is a 'fringe measurementsof bill length and central tail feathers, ex- species'amongst waders and waterfowl and woodland game, pressedas a ratio, allow adultmales and females to be con- and tendsto be neglectedin any group study.Woodcock fused: the best that can be done without dissection is to use enthusiastsare perhapsas odd and solitaryas the bird they the formula of Stronach, Harrington & Wilkins which have chosen,and the new Woodcock ResearchGroup of reducesthe probabilityof error to 28%: IWRB is strivingto flush someand induce flocking behav- iour. -0.2952 x bill length + 0.1566 x centraltail featherlength: [...] It seemsthat the occasionalWoodcock does get ringedby if greaterthan -8.3640 = male (72% correct),and theWSG - a total of five wasrecorded for 1974- thankyou, if less than -8.3640 = female (75% correct). TRG andHumber! The captureand ringing of this bird dur- ing its breedingseason really separatesthe men from the Birds in their first twelve monthsafter hatchingmust be boys,yet thereis a greatneed for 600-700, mainly pulli or excluded,and this can be done by examiningthe tips and juveniles,to be ringedin the BritishIsles each year. It has proximaledges of theouter primaries (ragged outline on first not beenmet since 1935 (763 pulli) and the averageyearly years;smooth on olderbirds, at leastuntil April) andthe ter- total, including FGs on migration, has been about 30 in minal lighter bar on primary coverts(broader and browner recentyears with pulli averagingabout 8. So every young on young birds). This quick, simple methodcorrectly clas- Woodcockringed will be a help. The recoveryrate is 7.9%. sifies 95-98%. Any Woodcock ringed during migration Two yearsago Ib Clausager(Ka10, Denmark) published periodsor in the winter is worth suchextra recordsin the a goodguide to methodsof determiningthe age-classand sex notebook.But can anyonesex Woodcockpulli? of Woodcock from external features. Even very precise

The value of bill lengths of museum specimens in biometric studies

RON SUMMERS

CultertyField Station, Newburgh, Ellon, Aberdeenshire, UK

Citation: Summers, R.W. 1976. The value of bill lengths of museum specimens in biometric studies. Wader Study Group Bull. 17:10-11.

The measurementof bill, wing, or any other structureis a onedoes not experiencesuch a complexsituation as seen in useful techniquein the study of migration (Evans 1964). Europe.One wouldtherefore expect the meanbill lengthsof However, the techniqueis fraught with problemswhich the freshlycollected birds and museumspecimens to be the make standardisation difficult. One of the difficulties is in the same. However, the table showsthat in the two species use of museummaterial. Standardbird text books give investigated,Turnstone Arenaria interpresand Sanderling biometricdata based on museumspecimens but the applica- Calidris alba, the museum birds tend to have lower bill tion of thesemeasurements to the field situationis problem- lengths. In the Turnstonethe difference amountsto 5.4% atical; e.g. it has been shownthat wings of museumskins (males) and 4.4% (females).These differences were highly shrink (Vepsalainen 1968, Green & Williams 1973). Bill significantin the Tumstone,but not in the Sanderlingwhere length,however, is believedto be the leastvariable of the the samplesize is smaller(Table 1). The explanationfor the biometricmeasurements though the possibilitythat the bills difference betweenthe two speciesmay lie partly in the of museumskins shrink has not beeninvestigated. structureof the bill, for in the Tumstonethe rhamphotheca I havethe opportunityto measurea seriesof freshlycol- (the hornysheath) extends further beyond the bonepoint of lected birds and to comparethem with skins from various the bill. The Sanderlingon the otherhand has a roundertip SouthAfrican museums(Cape Town, Pretoria,Durban, East to the bonearound which the rhamphotheca fits moreclosely London).Being at the tip of Africa it is likely that the birds (Figure 1). Shrinkageof the rhamphothecawill thereforebe of a given speciesare drawn from the sameorigin and that limited by the bone.

93 Bulletin 69 Special Issue July 1993 94 Wader Study Group Bulletin

Table 1. Mean bill lengthsof freshly collectedand museumskins of Turnstone and Sanderlingsfrom South Africa, Turnstone Fresh Museum skins

Mean_+SD n Mean _+SD n

Turnstone Sanderling Male 22.1+0.8 29 20.9+0.9 18 (t = 4.83, p < 0.001) Female 22.6+0.8 26 21.6+1.0 35 (t = 4.43, p < 0.001)

Sanderling Male 25.0+1.1 52 24.6+1.4 8 (t = 0.97, p < 0.1) Female 26.2+1.1 15 25.5+1.2 22 (t = 1.89, p < 0.05) Figure 1. Dorsal views of the bills of Turnstone and Sanderling showing the outlines of the bone and rham- photheca.

In conclusion,it appearsthat in the studyof thebiomet- References ricsof the Sanderling,and presumably other sandpipers, the problemof bill shrinkagein museummaterial will not be Evans,P.R. 1964. Wader measurementsand wadermigration. Bird Study importantwhen looking at grossdifferences but mustbe 11: 23-38. home in mind when dealingwith very small differences. Green,G.H. & Williams, A.L. 1973. Wading Bird Project.Report of the Universityof Dundee,North-East Greenland Expedition 1972. Howeverwith theTumstone, and perhaps other species, the Vepsalainen,K. 1968. Wing lengthof Lapwing(Vanellus vanellus) before bill lengthsof museumspecimens should not be used directly and after skinningwith remarkson measuringmethods. Ornis Fennica in biometric studies of live birds. 45: 124-126.

Seasonal changes in bill lengths of Knots, and a comment on bill measuring techniques for waders

MIKE PIENKOWSKI

Departmentof BiologicalSciencies, South Road, Universityof Durham,Durham, UK

Citation: Pienkowski, M.W. 1976. Seasonal changes in bill-length of Knots, and a comment on bill measuring techniques for waders. Wader Study Group Bull. 17: 12-14.

The problem numberof retrapswithin the sameyear hadbeen accumu- latedby theWash Wader Ringing Group and these data show Wing-lengthsand bill lengthsare the methodsat present thatthe seasonalchanges in the populationmeans were due mostused by ringersin orderto attemptto separate.wader to variationsin thebill-lengths of individualsduring the year. populations.The difficultiesin standardisingwing measure- Elsewhere, (Dick, Pienkowski, Waltner & Minton, in ments between different observers are notorious, and, even prep.),we haveshown that the seasonalchanges shown by when this is overcome,there may be problemsconcerned retrapdata are statisticallysignificant. with seasonalchanges of wing-lengthin individualbirds We cansuggest two possibleexplanations for a seasonal (Pienkowski & Minton 1973). The measurementof bill- changein measuredbill-length of an individualbird: lengthsis possiblyeasier to standardisebetween observers, but little attentionhas been given to the possibilityof sea- a. seasonalchanges at the feather-marginat thebase of the sonalchanges in these,although White & Gittens(1964) uppermandible associated with abrasionand moult; or subjectivelyconsidered seasonal changes in the bill shapes b. seasonalchanges in the growthor wear(or, perhaps,the of OystercatchersHaematopus ostralegus. degreeof compression)of the rhampotheca,perhaps While attemptingto separatePalearctic and Nearctic Knot relatedto feedingconditions. Calidriscanutus populations on thebasis of bill-lengths(to be publishedelsewhere), William Dick andI foundthat, in Effect b. hasbeen suggestedfor somebirds, especially mostareas, the meanbill-lengths of the Knotscaught varied passefines(e.g. Davis 1951, Stettenheim1972). It could cyclically (Figure 1). possiblyoccur in Oystercatchers(White & Gittens1964) and It wasclearly important to discoverif thevariations were TumstonesArenaria interpres(see Summers 1976), both of due to changesin the racial compositionof the flocksor to whichhave rhampothecae extending well beyondthe bone changesin bill-lengthsof individuals.Fortunately, a large structure;but this is not the casein the Knot andmany other

Bulletin 69 Special Issue July 1993