'Vol. XXIV •s•a HotaEasœr•,Banding Shorebirds in Southern Norway [147

BANDING SI{OREBIRDS IN SOUTHERN NORWAY BY HOLGER HOLC.ERSEN During recentyears, the bird ringing stationrun by the Zoological Departmentof the StayangerMuseum, on the coastof Jaerenin SW- Norway,has had markedsuccess with the trappingof adult shorebirds. A greatnumber of recoverieshave been reported from variouscountries, and theresults seem to havearoused a considerableinterest among .orni- thologistsand particularlyso amongbird r,ingers. It is a greatpleasure to informthe numerous readers of Bird-Banding in this way of the •nethodsused and someof :•heresults achieved. The trappingitself certainlyinvolves no magic. The natural con&itionsare by far the mostimportant feature, and in this respectthe museumof Stavangeris extremelyfortunate in beingsituated so near a placelike Revtangen. The ringingstation was founded in 1937by Mr. H. T.ho. L. Schaann- ing, until 1948 leaderof the Zool. Dept. of the •nuseum.Thus it had scarcelyshown its possibilitiesbefore the war broke .out, and during the yearsof Germanoccupation the wholearea was closeddue to mili- tary activities. But thosefew yearsof initial work before 1940 gave at onceinteresting yet fragmentaryresults, and when the war ended, no time waslost in re-establishingthe station,repairing the building, renewingthe traps and graduallyimproving them and increasingtheir number,and goingon wherethe work had so abruptlybeen stopped. The observatoryhouse is a smallhut only, with kitchen,one living- room,and two smallerrooms, each with two bunks.Most of the gear is kept in a shed where there are benchesand a table, and where the ringingwith its additionalwork of diary keeping,etc., can be carried out when the weather is not favorable for outdoor work. The ,observa- tory hut itself is well shelteredbehind the sand dunes,some few hun- dredmetres away from and out of sightof the actualtrapping place, while the shed is placedwith a full view of this place. Revtangen(58045 ' N. lat., 5030' E. long.) formsthe mostwesterly point of the coastalplain of Jaeren.The mile-long,sandy beaches here protrudein a low nazecovered with stones,or more correctly,in two suchnazes, the northernone being considerably shorter than the prin- cipal one. Thesenazes are of great importance.Around this corner or bendof the coast,the currentswill usuallyform somesort of eddy, whetherrunning from north to southor from southto north. On the shelteredside, loose artasses .of sea-weed, torn offby ,theswell from the rockybottom far out andaway, will be washedashore in varyingquan- tities. Betweenthe two nazes,there is a smallbut comparativelywell shelteredbight, and the beachof this is almost.always covered with a thick bed of sea.weed.Of course,the sea-weedwill occasionallybe washedoff againin roughweather, but whenthe last winteror spring stormshave passed, the beachis asa rulecovered to a greatextent with thesebeds of decayingseaplants, whioh are not washed away or moved until the late autumnbrings rough weatheragain. The rotting algaeproduce first of all a smellwhich can seem.rather strong,to a refinednose, but which is a necessaryingredient of the wholeaffair. Thissmell attracts hordes .of flies, diptera, whioh lay their 148] HOLt;ERSEN,Banding Shorebirds in Southern Norway Bird-Banding October eggson and in the weed-beds,where the larvae find shelter,a conven- iently high temperature,and food. At times the number of larvae can bc enormous,but it dependsupon the actual state of the sea-weed.If it is too dry, the larvaecannot develop; if it is too fresh,recently washed ashore,it is likewise of no use to them. So we can sometimesfind areas of sea-weedwhere larvae abound,whilst othersnearby are completely lifeless. But luckily enough,there is most often during autumn,when the migrantsare passingby, someplace or o•her on the beachwhere theplants are in the right stageof decay,and wherelarvae are plentiful. Thesedipterous larvae beloug to speciesidentified by Mr. J. Smart of Cambridge,England, as Coelopaeximia Stenh.and Coelopa/rigida (FIB.). They lorenthe principal,and ahnostonly, food for the flocks of shorebirdswhich migrate along the coastof Jaeren,when they stop at thoseplaces where such beds of nice-smellingsea-weed are to be found. Now, there are few .suchplaces, and at no other one than Bevtangeuis the quantityof food so great or so regular,nor is there sucha concentrationof wadersat otherplaces as there is on Bevtangen as a consequenceof the protrudinghaze. Besidethe preseBceof food, of pr,imaryimportance of course,as it makesthe wadersstop and as no artificial bait for thesebirds is known, thereis anothersignificant feature. At this part of the Norwegiancoast thereis practicallyno tide. The meandifference between high tide and low tide is only about30 centimetres[about one foot]. Thus no tide wavessweep away the sea-weedwhen the sea,is falling, to briBgit back for a short while only when the sea rises again. This means a constantshoreline, a non-changingfeeding-area for the birds, and, eventually,a constanttrapping-place for us, with the exceptionsindicated above, as the conditionsmay vary somcwhatfrom oneyear to another,but comparativelylittle within the sameseason. The birds are caughtin trapsmade of galvanizedwire-netting (•- inch mesh) on frames of sol•idsteel-wire. Various typeshave been tested,but thc best one seemsto be the triangular.type which is now being mostly used. The sidesare about1.3 metres[about 51 inches]long, the heightof the .trap is 35 cm. [about 14 inches]. One corner is cut off, and here is a trap-door,not usedfor catchingthe birds,but for gettingthem out of the trap and ,into a portablecage. There is no bottom in the trap and the roof has no entrances. These are to be found on the middle of thelong sides, one on each. The openingmeasures about 18 by 30 cms. [about 7Y2 by 12 inches],but it narrowsinward and endsin a small "door" or holejust wide and high enoughto let in suchbirds as Dunlin, Sanderling,Knot, Turnstone,and evenGodwit. The systemis more or less the same as .is used for instance in a bow-net, or in a lobster-wed. One trap alone doesnot catch very much. The averagecatch in- creaseswhen several traps are placedtogether, in the way that a long sidc of one will lead the birds toward the entrance of another, etc. As there is much food to be found also outsidethe traps,the birds will usuallyfirst pick up everythingthey can find easily withoutentering thesenetting-cages, wMch must after .all seemstrange to them. But whenthe trapsare placedon the sea-weed,or whenthey are re-setafter Vol. 1953XXIV HOLGERSEN,Banding Shorebirds in Southern Norway [149 havingbeen emptied, the upperlayer is turnedover and the deeperones with their freshsupplies of larvaeare exposed.Outside the traps,the food will eventuallydisappear, and as the birds are not able to dig very deep,they soonfind out that the only food left for them is that seenon the other side of the netting-wall. Somedo get in more or less by chance,and hereas so .oftenelse, when one is alreadyin, othersdo not hesitatein following. Sometimesthe birds may be very eagerto enter the traps, when they have eatenall accessiblefood outside,but it may happenthat hundredsof waderswalk aroundthe trapsand feed, and not one getsin. From time to time all traps are emptiedand the birds carried in .the portablecages to dry land, i.e. the elevateddunes or the shed,to be ringed. How oftenthis is donevaries considerably, but the traps are alwayslooked after in the early morning,when reset in theevening, and duringthe day theyare usuallykept under observation, so that the birds are never retained.too long. However,they do not seemto be much worried, tame as wadersin autumn often are. Having discoveredthat theydo not find any way out, theymay evenperch on the entrancetun- nel, put the bill underthe dorsalfeathers, and fall asleep. Due to the varying natural conditions(food, weather) the annual catchmay vary considerably.The trappingseason is usuallybetween mid-Augustand mid-October,i.e. two monthsyearly. For the most importantspedes, Table 1 showsthe resultsfor the last four years:

TABLE 1 S•mcms: 1949 1950 1951 1952 Knot, Calidris canutus 761 226 408 145 Dunlin, Cal. alpina 663 1667 2344 2197 Curlew-Sandpiper,Cal. testacea 19 50 38 8 Little Stint, Cal. minuta 6 23 80 9 Sanderling, Crocethia alba 299 183 369 181 Turnstone,Arenaria interpres 96 66 149 36 Ringed Plover, Charadrius'hiaticula 148 85 96 48 GreyPlover, Squatorola squatarota 14 7 '•' 7 17 R.ff, Philomachuspugnax 11 -- 2 -- Bar-tailed Godwit, Limosa lapponica 138 •'46 18 7 Redshank, Tringa tetanus 20 241 29 3

2175 2377 3540 2651 The great increasein the nmnberof ringedDunlins is mainly due to a greaternumber of improvedtraps being used, whilst the Knot and the Godwithave not beenpresent in the samenumbers during the last years as before. It will'b•seen that thesebirds, with the exceptionof the Ruff, are mainly littoral species.Inland waders,landbirds like Dotterel,Golden Plover,Curlew, Whi•nbrel, and Lapwing,are not trappedhere. Other speciescaught in .the sametraps and on the sa•nespot, are Starling (Sturnusvulgaris), Rock pipit (Anthus spinoletta),White Wagtail (Motacillaalba), occasionallyOystercatcher (Haematopus ostralegus) andPurple Sandpiper (Calidris mariti•na), only the twofirst onesbeing trappedin any numbers(1952 resp.706 and 100). Table 2 showsthe grandtotal ringedof the sa•nespecies as above, with number of recoveries. Bird-Banding ]].50] HOLCERSEN,Banding Shorebirds in Southern Norway October 'Vol. 1953XXIV '.•OLGERSEN,Banding Shorebirds in Southern Norway ['15]_ Bird-Banding ].52] HOLGERSEN,Banding Shorebirds in Southern Norway October

ß Tr;ngatotanus 0 Cal. minuta /• Cal. testacea •'! Phil.pugnax I•] Char.hlaticula • Sq.squafarola

• Popenqu•ne,Senegal • ;' •'Dakar, St.Senegal Louis,Senegal

TABLE 2 1) SPECIES: Nos. RINGED: RECOVEamS: % Grey Plover 67 5 7.5 Bar-tailed Godwit 429 27 6.3 Turnstone 819 47 5.7 Redshank 231 9 3.9 Knot 2,924 109 3.7 IJttle Stint 187 7 3.7 Ruff '. 112 3 2.7 Sanderling 1,590 31 1.95 Dunlin .: 11,103 142 1.3 Curlew-Sandpiper 180 2 1.1 RingedPlover 621 6 0.97

-- 18,263 388 2.1 1) •byJune, 1953 It is not unreasonablethat thosetopping the list are big birdslike GreyPlover and Godwit, followed by Turnstone,Redshank, and Knot. ol. xxiv 1953 HOLGERSEN,Banding Shorebirds in Southern Norway [153

Iost of the recoveriesare dueto .thebirds being shot, and the hunters, f course,look first for the biggerbirds. Somewhatunexpected is the igh percentagefor LittleStint, bu.t this may be justan accident.1.2% eeoveriesfor Dunlin is not much,but dueto the high numberringed f thisspecies, recoveries are many and give a goodpicture of its migra- ton routesand winter quarters. Most of thesebirds havebeen on their way southfor sometime al- eadywhen they are.trapped at Revtangen.Some are no doubtbreeding ,irds from the nearestbeaches and fieldsor marshes(Ringed Plover, tedshank,Dunlin). Where the bulk do come from is difficult to find ,ut, as the breedinggrounds for a great part of the 'birds must be trctie regionswith no humanpopulation. Correspondingly, recoveries rom the breec[ingseason or breedingareas are extremelyscarce: One •not was reportedfrom W. Greenland;one Bar-tailedGodwit from the krchangeldistrict in N. Russia; one Knot and one Turnstonewere rappedand releasedin May in SW-Ieeland,presumably on their way o Greenland. Threeof our Dunlinshave been taken in anotherseason by the Swed- shbird observatory and ringing station at Ottenby in Gland;one Turn- ;tonein mid-Julyfive yearsafter ringing, on the northernBaltic coast )f Sweden; and a Knot and a Turnstone,as mentioned,in Iceland. On he otherhand, a Swedish-ringedDunlin from Ottenbywas trapped at .:[evtangentwo yearslater. It is to be hopedthat increasedactivities it the variousshore ringing stationswill give more suchresults in future. Most of the recoveriesare reportedfrom countriesvisited by the birdswhen they leave Norway shortly after havingbeen 'banded. Some Jo crossthe North Sea,as is demonstratedby a few Godwitsand Dun- lins. But the major part go south,cross the Skagerrakto Denmark, and continueSW. The winter-quartersare partly in the British Isles, partlyalong the coastsof France,for somespecies also on the Iberian Peninsula. Many of the species,but perhapsnot many individuals, extendtheir migration so far southas the NW coastsof Africa. For details,see the accompanyingmaps. A few examplesof longevity,as shownby recoveries:Knot, 6, 7, and 9 years; Dunlin, 14•/•; Turnstone,4 and 5 years; Bar-tailedGodwit, 4, 5, and 7 years. Finally onerather remarkable recovery: two Knots,Nos. 11,588and 11,587, wereboth ringedat Revtangenon August23, 1949. More than a year later, on October17, 1950, they were both (togetherwith an unmarkedbird) shotout of a flockof four at Nord-Mors,Limfjorden, Denmark. That theyhad kepttogether during the winterof 1949/1950 is likely, but what had they done in the summerof 19507 Had they beenback to theirArctic breeding grounds, or hadthey stayed together somewherein the North Sea area, withoutbreeding? The recoveryis, however,not unique:Two HoodedCrows (Corvus cotonecornix), 'both ringed in the .sametrap in Stayangeron February 13, 1942,were trapped together on January2, 1946,in .Moss,290 kilo- metreseast of the rin•ng-plaee. S•avangerMuseum, Zool. Dept., Stayanger,Norway.

[