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Occurrence and passageof Wood glareola and Tringa chloropuson the Dravsko polje, north- eastern Slovenia

Milan Vogrin

Vogrin,M. 1998. Occurrenceand passage of WoodSandpiper Tringa glareolaand Green Sandpiper Tringa chloropuson theDravsko polje, north-eastern Slovenia. Study Group Bull. 87' 55-58.

This paperdescribes the occurrenceof the WoodSandpiper and the GreenSandpiper in north-easternSlovenia in 1984- 1997. The WoodSandpiper is a regularmigrant between March andSeptember, whereas the GreenSandpiper is present throughoutthe season.The differencesbetween years in bothspecies is significantwhereas between months it is not (Kruskal-Wallistest). Both speciesare dependentduring migration on drainedponds and reservoirs (66% of T. ochropus and 85% of T. glareola respectively).

Milan Vogrin,Hotinjska c. 108, S1-2312Orehova vas, Slovenia. E-maih [email protected]

INTRODUCTION Sandpiperwere gatheredduring censuses at differentlocalities The WoodSandpiper Tringa glareolaand the GreenSandpiper andhabitats throughout the studyarea. Censusesand visitsto Tringa ochropushave beenstudied extensively on the localitieswere randomly chosen throughout the study. In breedinggrounds in northernEurope (e.g. Glutz Von general,it waspossible to avoiddisturbing during Blotzheimet al. 1977, Cramp& Simmons1983 and censuses.However, occasionally were flushed referencestherein). On the otherhand, little quantitative duringcounts. Usually, complete counts were obtainedbefore informationis availablefrom migrationin CentralEurope, the birdsflew andoften it waspossible to seewhere they went althoughbreeding biology in this regionhas received more (e.g.in complexof Raceponds), thus avoiding double- attention(e.g. Kraatz & Beyer 1982, Kraatz & Beyer 1984, counting. Data from the river Drava (on the borderwith the Zdarek 1994, Zavadil 1995). Therefore,the aim of the present studyarea) are not takeninto accountin this study. articleis to describethe occurrenceand migration pattern of bothspecies in north-easternSlovenia. All statisticaltests were performed with the SPSS6.0 statisticalpackage, and a nonparametricKruskal-Wallis one- STUDY AREA way ANOVA test was carriedout (Sokal & Rohlf 1995) to Dravskopolje (about 210 km2) is locatedin north-eastern comparenumbers recorded in differentmonths and years. Slovenia(approximately 46ø25'N, 15ø45'E; Figure 1) andis oneof the largestagricultural areas in the lowlandpart of RESULTS Slovenia.Throughout the countrythere are alsonumerous WoodSandpiper Tringa glareola and Green Sandpiper Tringa man-madewater bodies(i.e. fish ponds,reservoirs, gravel pits) ochropusare two of themost abundant of nonbreeding small townsand villages. The most importantstanding water shorebirdon theDravsko polje during migration (pets. obs.). bodiesin this area for waterbirdsare fishponds(Race), Overthe whole study period both species used drained ponds reservoirs(Pozeg and Medvedce),and somegravel pits. Most andreservoirs more often then other habitats for feedingand flowing watersare canalsand regulated streams. resting(Table 1).

Table 1. The usageof habitattypes (in %) by Tringaochropus and Tringa The areabelongs to the sub-Pannonicphytogeographical area glareolawithin the studyarea during 1984 -1997. (Madn•ek 1987) and the climateis moderatelyContinental (Furlan 1990). A detail descriptionof the studyarea and habitatshas been given elsewhere(Vogrin & Orgo 1995, drained ponds other water arable Vogrin 1996, Vogrin 1997a,Vogrin 1997b). and reservoirs bodies lands

METHODS Tringa ochropus 66 27 7 Data were collectedbetween 1984 and 1997 during all Tringa glareola 75 21 4 months. Field data for the Wood Sandpiperand the Green 56

Green Sandpiper Tringa ochropus Chi-square)= 6.17, df = 5, P> 0.05). The highestdaily count GreenSandpipers are regularlyobserved throughout all was54 in April 1993. seasons,however during late autumnand winter they become muchmore rare. Only occasionalmigrants are observedin More pronouncedmigration took place in 1984, 1993and June. The first migrantsusually appear in the f•rst weekin 1996 (Figure4), but the exactreasons for this are unknown. March. Peaknumbers in springoccur in May, whereasthe The differencesbetween years was significant(Kruskal-Wallis autumnmigration is lesspronounced (Figure 1). Nevertheless test,Chi-square = 19.95,df = 10, P < 0.05). the differencesbetween months in averagenumbers of observedindividuals was not significant(Kmskal-Wallis test, Chi-square= 8.90, df = 5, P > 0.05). The differencewas not significanteven between spring months (Kruskal-Wallis test, Chi-square= 5.63, df = 2, P > 0.05). The largestnumber countedin one day was 79 in May 1986.

April june August May July September

Month

Figure3 Migrationpattern of theWood Sandpiper Tringa glareola on the Dravskopolje in the northeasternSlovenia in differentmonths. July September MarchApril June August

Month

Figure 1 Migrationpattern of the GreenSandpiper Tringa ochropus on the Dravskopolio in the northeasternSlovenia in differentmonths.

Year

Figure4 Migrationpattern of theWood Sandpiper Tringa glareola on the Dravskopolje in differentyears. 84 8 86 87 88 90 91 92 93 96 97 DISCUSSION Year For bothspecies it is well knownthat birds migrate on a broad Figure2 Migrationpattern of the GreenSandpiper Tringa ochropus on the frontacross (e.g. Cramp & Simmons1983, Colston & Dravskopolio in differentyears. Burton 1988). We must also take into account that both The averagenumbers of migrantsin differentyears is present speciesalso migrate during the night(Zalakevi•ius et al. 1995) in Figure2. The largestaverage number of GreenSandpipers andthus the numbers of bothspecies are surely was observedin 1986. The differencesbetween years in underestimates.There is little relevantprevious work with averagenumbers of observedindividuals was highly whichto comparethe results of thepresent study, although significant(Kruskal-Wallis test, Chi-square = 25.92,df = 10, P wherecomparisons are possible, the articles present data from < 0.005). onlyone or twoseasons. According to Cramp& Simmons (1983)and Colston & Burton(1988), spring passage of the Wood SandpiperTringa glareola GreenSandpiper begins in Marchand is completedin May. In Wood Sandpiperson the Dravskopolje are recordedbetween my studyarea this is onlypartly true; on theDravsko polje, Marchand September. The first migrantsin springappear in peakspring passage of GreenSandpipers occurred in May. In March,but a larger-scalemigration starts in April (Figure3). autumn,the main passage period is in Julyand August (Cramp During the autumn,the WoodSandpiper is a regularmigrant & Simmons1983), and this is trueof my studyarea as well. in smallernumbers. In spiteof this difference,there was no difference in numbersbetween months (Kruskal-Wallis test, The numberof individualsof bothspecies occurring on the Dravskopolje was similar to theresults obtained by Musil 57

(1995) on fishpondsin theTrebon basin, Czech Republic shallowwater, and as suchare of little interestfor sandpipers between1988 - 1995. In Vojvodina(northern part of Serbia), (Smith et al. 1992) should be taken into account. theGreen Sandpiper was also a regularmigrant between 1966- 1974(Dimitrijevia• 1977). Springmigration in Vojvodinais ACKNOWLEDGEMENTS lesspronounced then on theDravsko polje. On theother hand, All of the fieldwork on which this paperis basedwas carried in Vojvodinaautumn migration is in two waves:the mainone out by the authorwith the assistanceof my wife Nusa and duringAugust, and the secondone during October Marjan Vogrin,to whom I am particularlygrateful. I am also (Dimitrijevia•1977). Neverthelessthe average number of indebted to K. Smith for critical comments on the first draft of individualsper month is similaror evena little lowerthan that the manuscriptand for additionalliterature on the abovetopics. on the Dravskopolje. REFERENCES The WoodSandpiper in Vojvodinaand in Seewinkel(Austria) Bukacinska,M., Bukacinski,D., Cygan, J.P.,Dobrowolski, reachedpeak numbers in spring,during late April or earlyMay K.A. & Kaczmarek,W. 1996.The importanceof fishpondsto respectively(Dimitrijevia• 1977, Winklet & Herzig-Straschil waterfowlin Poland.Acta Hydrobiol.37 (supplement1): 57- 1981), similarto'my results. During autumnmigration, in 73. Vojvodina,peak numbers occurred during July or in mid August. Howeverin north-easternSlovenia this species Colston,P. & Burton, P. 1988. Afield guide to the Wadersof migratesthroughout the autumnwithout any noticeable peak Britain and Europewith North and the Middle East. (seeFigure 4). The highestdaily countin Vojvodinawas up to Hodder & Stoughton. 600 individualsin July (Dimitrijevia• 1977), howeverthe averagenumber of individualsthroughout the seasonis similar Cramp,S. & K.E.L. Simmons(ed.) 1983. The Birdsof the on Dravskopolje. Kmecl & Riffnet(1993) presentdata for WesternPalearctic. Vol. 3. Oxford University Press.Oxford. WoodSandpiper passage through Lake Cerknica(south-west Slovenia)for 1991 and 1992. However, the authorspresent Dimitrijevia•,S. 1977. [Charadriiformesin the Provinceof maximumWood Sandpiper numbers per pentad,so a direct Vojvodina].Larus 29-30: 5-32. (In Serbianwith English comparisonis not possible. Summary).

The key factorswhich influence habitat selection by migrant Ens, B.J., Piersma,T. & Drent, R.H. 1994. The dependenceof waterbirdsduring the nonbreedingseason are availabilityof wadersand waterfowlmigrating along the EastAtlantic food, saferoosting sites and the extentof disturbance(e.g. Flyway on their coastalfood supplies:What is the most Myers1984, Ens et al. 1990,Ens et al. 1994).On the Dravsko profitableresearch programme? Ophelia 6 (Suppl.): 127-151. poljethere are numerous water bodies, especially fish ponds, which serveas feeding and roosting sites for many waterbirds Ens, B.J., Piersma, T., Wolff, W.J. & Zwarts, L. 1990. (Vogrinpets. obs.). Homewardbound: Problems face when migratingfrom the Banc d'Arquin,Mauretania, to their northernbreeding Water level fluctuations are a dominant feature in groundsin spring.Ardea 78: 1-16. and can determinewetland use by waterbirdsthrough effects on food availability(e.g. Kushlan 1989, Ntiamoa-Baidu et al. Furlan,D., 1990. [Das klima der gegendzwischen dem 1998). When the water level falls, aquaticprey becomemore Pohorjeund dem Bo•]. Zbornik ob&ineSlovenska Bistrica: concentratedand thus more available,especially for those 332-347. (in Slovene,with a summaryin German). specieswhich prefer shallow water, e.g. for Greenand Wood Sandpipers(Cramp & Simmons1983, Ntiamoa-Baidu et al. Glutz von Blotzheim, U.N., Bauer, K.M.& Bezzel, E. 1977. 1998). Habitatswhere water levelsfluctuate periodically on Handbuchder VogelMitteleuropas. 2. Teil. theDravsko polje are fishponds and other water bodies which Band 7. AVG Wiesbaden. serveas extensivefish farms (e.g. reservoirs). Every year (usuallyfrom March - May and/orbetween September - Kmecl, P. & Rizner,K. 1993. [Surveyof the waterfowland November),some ponds are drainedand the fish areharvested birdsof prey of Lake Cerknicawith emphasison their passage with the useof a seinenet over a numberof days. The ponds and wintering].Acrocephalus 14:4-31. are refloodedwith water from the neighbouringpond or canals.The partialspring and/or autumn drying of fishponds Kraatz, S. & Beyer,K.H. 1982. Zur Brutbiologiedes thereforepositively influences the numbers of migrating Waldwasserlaufers(Tringa ochropusL.). Beitr, Vogelkd.28: waders(see also Bukacinska et al. 1996). In my studyarea 321-356. this was the casefor Greenand Wood Sandpipers,which are highlydependent on drainedponds and reservoirs. On the Kraatz, S. & Beyer,K.H. 1984. WeitereBeobachtungen zur otherhand, the fact that,during these seasons, flowing water Brutbiologiedes Waldwasserlaufers (Tringa ochropusL.). sitesare fully vegetated,with little exposedmud or open Beitr. Vogelkd.30: 33-47. 58

Kushlan,J. 1989. Avian useof fluctuating wetlands.In: Vogrin,M. 1997a.Niche separationof the MarshHarrier Sharitz, R.R. & Gibbons, J.W. (eds.): Freshwater Wetlands and (Circusaeruginosus) and Hen Harrier(Circus cyaneus) during Wildlife. United StatesDepartment of the Environment. migrationthrough Dravsko polje (NE Slovenia).Buteo 9:31- Virginia. pp. 593-604. 33. 1997.

Mafinbek,L. 1987. Bukovigozdovi na slovenskem.Delavska Vogrin,M. 1997b.Breeding Tufted Duck in theDravsko polje, enomostLjubljana. pp 153. north-eastSlovenia. Duck SpecialistGroup Bulletin 1: 10-12. IUCN, Wetlands International. Musil, P. 1995. [Changesin numbersof water and birds onfishponds in the TrebonBasin in 1988-1995]. In: Hora Vogrin,M. In press. Migrationpatterns of the Cormnon J., J. Plesnik& J. Jandova(eds.): Vyznamna ptabi uzemi v SandpiperActitis hypoleucos and its habitatchoice during •eskeRepublice. Sbornik referam Kostelec nad •emymi lesy, migrationin northeasternSlovenia. Avocetta. 7-8. dubna1995. Praha.pp. 25-33. (In Czechwith English summary). Vogrin,M andZorgo A. 1995.Great Cormorant Phalacrocoraxcarbo at fishrearing ponds in NE Slovenia. Myers, J.P.1984. Spacingbehavior of non-breeding Acrocephalus16: 152-155. (In Slovenewith English shorebirds. Behav. Mar. Anim. 6: 273-323. summary). W'mkler,von Hans & Herzig-Straschil,B. 1981.Die Ntiamoa-Baidu,Y., Piersma,T., Wiersma,P., Poot, M., Battley, Ph'finologieder Limikolen im Seewinkel(Burgeland) in der P. & Gordon,C. 1998.Water depth selection, daily feeding Jahren1963 bis 1972.Egretta 24: 47-69. routinesand dietsof waterbirdsin coastallagoons in Ghana. Ibis 140: 89-103. Zavadil,V. 1995.[Breeding of theGreen Sandpiper (Tringa ochropus)in formermilitary area Ralsko (North Behemia)]. Smith, K.W., Reed, J.M. & Trevis, B.E. 1992. Habitat use and ZpravyfESO 41: 9-10. (In Czech with English summary). sitefidelity of GreenSandpipers Tringa ochropus wintering in SouthernEngland. Study39: 155-164. Zalakevibius,M., Vafias,S., Stanevibius,V. & Vaitkus,G. 1995.& winteringin Lithuania.Acta Sokal,R.R. & Rohlf, EJ. 1995.Biometry. The principles and ZoologicaLituanica, Ornithologia 2: a monograph. practice of statisticsin biologicalresearch. W.H. Freemanand Company.New York. Zdarek,P. 1994. [Nestingof GreenSandpiper (Tringa ochropus)in Bohemia].Sylvia 30: 91-96. (In Czechwith Vogrin, M. 1996. [Breedersof wet meadowsat Medvedce Englishsummary). impoundingresrvoir on Dravskopolje]. Acrocephalus 17: 61- 71.