Summering Coastal Waders on Fuerteventura, Canary Islands, Spain

Summering coastal waders on Fuerteventura, Canary Islands, Spain

Juan A. Lorenzo & Keith W. Emmerson ß

Lorenzo,J.A. & Emmerson,KoWo 1996. Summeringcoastal waders on Fuerteventura,Canary Islands,Spain. WaderStudy Group Bull. 79: 87-90. Data on the abundanceand richnessof waders summeringon the island of Fuerteventura (CanaryIslands) is presented. Fewerbirds occur here than at siteson the adjacentWest Africancoast, though the speciescomposition is similar. Waders showa strongpreference for coastalareas with soft substrates(mudflats and sandy beaches) as opposedto those with hard or mixedsubstrates (intertidal lava platformsand pebblebeaches), a situationwhich contrasts markedlywith that of the winteringwader community.The numberof summeringwaders represents27.1% of the wintertotal, and the majorityof individualsare juveniles. The summeringpopulation of WhimbrelsNumenius phaeopus is similarin size to the wintering populationwhich is nationallyimportant. JuanA. Lorenzo& Keith WoEmmerson, Departamento de BiologfaAnimal (Zoologfa), Facultad de Biologfa,Universidad cle La Laguna,38206 La Laguna, Tenerife,Islas Canarias,Spain.

INTRODUCTION Variablesconsidered were abundance(total numberof birds),species richness (total number of species),length The Canary Islandsare situatedon the western extreme of of coastalarea and substratetype. The latterwere the East AtlanticFlyway. Duringwinter, 3,000-4,000 classifiedinto three principalcategories: soft (sandy wadersare presentin this archipelago(Emmerson & beaches, mudflats,etc.), hard (intertidallava platforms Lorenzoin prep.)ø More birdsuse the islandsas a and pebblebeaches) and mixedcoast (a combinationof stopoversite during migration periods, but there is no the previoustwo). publishedinformation in summer. As notedby Van Dijk et al. (1990), summeringwaders have been lessstudied than A SpearmanRank Correlationwas carriedout to compare those that are breeding,wintering or on migration. abundanceand speciesrichness with the lengthof Moreover,Smit & Piersma(1989) stressedthe need for coastlinesurveyed and the frequencyof occurrenceof studiesof the size and compositionof summerwader birds'ineach habitat type. The G-test was used to communitiesalong the East AtlanticFlyway, a continuing determinestatistically significant differences between and importantgap in existingknowledge. variablefrequencies.

In this paper,we presentinformation about coastal wader communitiesduring summer on Fuerteventura,an eastern islandof the CanaryArchipelago (Figure 1).

STUDY AREA AND METHODS

Fuerteventurais semi-aridand highlyeroded, with importantpotential habitats for winteringcoastal waders (sandybeaches, intertidal lava platforms,mudflats, etc.). Its total coastlinemeasures 321.1 km of whichonly 157.3 km (49.4%) representssuitable wader habitaton the basis of its physicalconstitution (intertidal lava platforms, mudflatsand sandybeaches). However,a previousstudy demonstratedthat only35.7 km (22.7%) of this potential habitatharboured high concentrationsof waders (Emmerson1988). The eight localitiesconsidered in the presentstudy cover this lengthof coastline(Figure 1) for whichinformation about substrate type and length censusedis given in Table 1.

Censuseswere carriedout duringthe thirdweek of June 1989 and consistedof lineartransects along the shoreline duringlow tide when mostbirds were activelyfeeding. Figure1. Mapof Fuerteventura(Canary Islands) showing survey sites(numbering designation of sitescorrespond to thatof Table 1).

87 Table1. Kilometressurveyed and •ubstrate type of the localities RESULTS censusedon FuerteventuraoLocation of sitesshown in Figure1• A total of 35.7 km were surveyed duringthe study. The Localities Length Substrate type resultsof the censusesare presentedin Table 2. A total (km) of 453 birdsof 13 specieswere recorded.The locality 1 Sotavento 5.1 Soft,sandy beach and intertidal withthe maximumvalues of abundanceand species mudflat richnessWas Sotavent0 (226 birdsand 10 species),whilst 2 Cotillo 7.2 Mixed,intertidal lava platformand the lowestvalues were found at the rockycoast of La mud fiat Lajita(only nine birdsand two species). 3 Majanicho 8.3 Hard,intertidal lava platform Duringthe summer,as in winter, KentishPlover 4 El Matorral 1.3 Mixed,intertidal lava platformand Charadriusalexandrinus is by far the commonestwader supratidallagoon (Table2). Otherspecies present in relativelyhigh 5 Corralejo 4.8 Mixed,intertidal lava platform and numberswere Grey PloverPluvialis squatarola, Whimbrel sandybeach Numeniusphaeopus and TurnstoneArenaria interpres. The remainingspecies are rare, mostaccounting for less 6 LaLajita 2.3 Hard,intertidal lava platform and than 1% of the total. pebblebeach 7 Caletade 4.6 Mixed,intertidal lava platformand Table3 presentsthe numberof wadersrecorded at each Fuste mudflat localityduring winter 1990/91 comparedwith the present 8 Puertode 2.1 Hard, intertidallava platformand study. The presenceof summeringbirds differed Rosario pebblebeach strikinglybetween species, varying between less than 5%

Table 2. Combinedcensus results,abundance and species richness.

Species I 2 3 4 5 6 7 8 Total % of total

RingedPlover Charadnushia•cula 1 3 5 3 12 2.6 Kentish Plover Charadrius alexandrinus 202 64 8 i0 33 18 10 352 77.7 GreyPlover Pluvialis squatarola 8 2 2 2 4 5 23 5.1

Knot Calidris canutus 1 1 0.2

SanderlingCalidris alba 5 5 1.1 DunlinCalidris alpina 1 1 0.2 Bar-tailedGodwit Limosa lapponica 1 2 3 0.7 WhimbrelNumenius phaeopus 3 10 3 4 2 6 1 • 6.4 CurlewNumenius arquata 1 1 0.2 RedshankTdnga totanus 1 1 1 3 0.7 GreenshankTringa nebularia 2 2 0.4 CommonSandpiper Actitis hypoleucos 1 1 0.2 TurnstoneArenaria interpres 4 12 1 • 4.4

Abundance(total number of birds) 226 85 26 16 43 9 35 13 453

Richness(total number of species) 10 6 5 4 ,4 2 5 4 13

of the winteringpopulation to nearly50% or even more. were. The lengthof coast surveyedis not correlatedwith Withrespect to summeringKentish Plover, most birds eitherthe abundance of birds or with richness{rs=0.643, wereprobably of the localbreeding population. Whimbrel d.f.=8, p=0.089and rs=0.687,d.f.=8, p=0.068, wasthe onlyspecies to maintainsimilar population levels respectively).Thus the differencesin the lengthof the duringboth seasons. differentcoasts surveyed did not accountfor the differences in the numbers of birds recorded at those The abundancevalues are significantlycorrelated with locations. speciesrichness (rs=0.847, d.f.=8, p=0.025),in other words,the morespecies there were, the morebirds there The number of censuses undertaken in each substrate

88 type did not differ statistically(G=1.836, d.f.=2, N.So)and postnuptialmigration commenced in July (Lorenzo1993). thus, the resultscan be consideredrepresentative of the Similartimings have also been documentedon the West community.The proportionof the total on each substrate Africancoast (Cabo & Sanchez 1985; Piersmaet aL 1987; is shown in Table 4. More birdsand species occurredon Zwarts & Piersma 1990; Piersma etaL 1990). soft habitatsfollowed by mixedcoast and finallyhard substrate coast. Table 4. Totalsand percentagesof waderssummering on each substratetype on Fuerteventura(H: hard substrate,S: softsubstrate, The abundanceof waders in each habitattype differed M: mixed substrate). significantly(G--132.9, d.f.=2, p<<0.01), but species Percentageof birds richnessdid not (G=0.70, d.f.=2, N.S.). Knot Calidris Species/ habitattype S H M canutus,Sanderling Calidris alba, Dunlin Calidrisalpina % (n) % (n) % (n) and Greenshank Tringanebularia showed a marked preferencefor soft substrateswhereas Curlew Numenius RingedPlover Charadrius 8.3 (1) 41.7 (5) 50.0 (6) arquataand CommonSandpiper Actitis hypoleucos hiaticula KentishPlover Charadrius 57.4 (202) 7.1 (25) 35.5 (125) preferredintertidal lava platformsøThe remainingspecies alexandrinus appearedin eithertwo or three of the habitattypes• The Grey PloverPluvialis 34.8 (8) 8.6(2) 56.5 (13) overallabundance of each specieswas positively squatarola correlatedwith the numberof habitattypes it used (rs= Knot Calidriscanutus 100.0 (1) 00769, d.f.=13, p=0o007)o SanderlingCalidris alba 100.0 (5) Dunlin Calidrisalpina 100.0 (1) Table3. Numbersand percentageof waderspecies wintering and Bar-tailedGodwit Limosa 33.3 (1) 66.6 (2) summeringat studysites on Fuerteventura. lappon/ca Whimbrel Numenius 44.8 (13) 55.2 (16) % of w•nter Species/ season Winter Summe phaeopus r total occursrig •n Curlew Numenius arquata 100.0 (1) summe, Redshank Tringatotanus 33.3 (1) 33.3 (1) 33,3 (1) Greenshank Tringa 100,0 (2) RingedPlover Charadr/us 128 12 94 nebularia h/at/cula CommonSandpiper Actiris 100.0 (1) Kentish Plover Charadrius 215 352 61,1 hypoleucos alexandrinus" TurnstoneArenaria 20.0 (4) 80.0 (16) Grey Plover Pluvialissquatarola 115 23 20,0 interpres Knot Calidris canutus 3 1 33,3 SanderlingCalidris alba 90 5 5.5 Total 49.9 (226) 10.6 (48) 39.5 (179) Dunlin Caliddsalpina 29 1 3.4 Bar-tailed Godwit Limosa 11 3 27,3 lapponica Whimbrel Numeniusphaeopus 31 29 93,5 Fuerteventura harbours low numbers of waders Curlew Numeniusarquata 1 (comparedto West Africancoastal areas) as also is the Redshank Tringatotanus 8 3 37.5 case elsewherein the archipelago,and indeed only3,000- GreenshankTringa nebularia 4 2 50.0 4,000 waders over-winter(Emmerson & Lorenzoin prep). CommonSandpiper Actitis 26 1 3.8 It is not possibleto obtainthe total number of waders hypoleucos summeringon Fuerteventuraby simplyextrapolating the TurnstoneArenaria interpres 142 20 14o1 numbercensused in differenthabitat types to the total Total 372 101 extentionof these habitatsas undertakenby Piersma (1986) in April 1986 on three islands. Waders tend to use becauseKentish Plover is a breedingspecies (Lorenzo & Emmerson1995) it is not includedin t•e total. specificareas in the Canary Islands,and, moreover,they are encounteredin irregularconcentrations along the When comparingwinter and summersubstrate coast, possiblydue to variationsin, for example, preferencesof waders on the Fuerteventurancoast, the invertebrateproductivity and the degree of human disturbance. Such circumstances have been detected in overalldistribution appears to be different(G=60.72, d.f.=2, p<<0.01), as more birdsare presenton hard other areas (Recher 1966; Wolff 1969; Dominguez 1989; substratecoast duringthe winter than in the summer, Goss-Custard& Durell 1990; Kirby etal. 1991; Mouritsen when soft substratecoast was the preferredhabitat. & Jensen 1992; Nehls & Tiedmann 1993). This is also the Furthermore,at the eight localitiesno correlationexists case on Fuerteventura,as shownby the fact that the between numbers counted in summer with those of winter abundanceof birdsor richnessof specieswas not (rs=0.5714, d.f.=8, p=0.1306). correlatedwith lengthof habitatat each locality.

The overallpercentage of waders spendingthe summer DISCUSSION on the coast of Fuerteventurarepresents 27.1% of the numbers counted at the same sites in winter, and The June date of the studyshould imply that the waders correspondsreasonably well withthe reportsfor other recordedwere summeringbirds and not migrants wetlands in other sites (Van Dijk et aL 1990). However, departinglate or returningearly. Duringthe same year on the winter countsused in this comparisonare from the Tenerife, prenuptialmigration finished in May and precedingwinter 1990/91 (Emmerson & Lorenzoin prep.) and one thereforehas to bear in mindthe possibilityof

89 significantbetween year variations inpopulation size. No Ardea 78(2): 301-314. majorchanges, however, were detectedon Tenerife Goss-Custard,J.D. & Durell,S.E.A. 1990. Bird behaviourand between 1989/90 and 1990/91 winter censuses and thus environmentalplanning: approaches in thestudy of wader the same situation has been assumed for Fuerteventura. populations.Ibis 132: 273-289. Kirby,J., Cartreel,S. & Green, M. 1991. Distributionand habitat As regardsindividual species, Fuerteventura could be an preferencesof waderswintering on the non-estuarinewest importantsummering area for Whimbrel,the only species coast of Ireland. Irish Birds 4: 317-334. for which the number recorded in summer was similar to that in winter. Emmerson& Lorenzo(in prep.) indicate Lorenzo,J.A. 1993. Descripci•Snde la comunidadde aveslira[colas that the winteringCanarian population represents 63.6% de El IVl•dano(Tenerife, Islas Canarias) durante un ciclo of total Spanishwinter numbers. anual. Ardeo/a40(1): 13-19. Lorenzo, J.A. & Emmerson, K.W. 1995. Recent infromation on the The speciescomposition of the summeringpopulation is distributionand statusof the breedingpopulation of Kentish more or less similar to that found on the West African PloverCharadrius alexandrinus in the Canary Islands. Wader coast, althoughOystercatcher Haernatopus ostra/egus, Study GroupBulletin 76: 43-46. LittleStint Ca/idrisrninuta and CurlewSandpiper Ca/idris Mouritsen, K.N. & Jensen, KT. 1992. Choice of microhabitatin ferrugineaare notablyabsent on Fuerteventura. tactileforaging dunlins Calidris alpina: the importanceof Accordingto Summers eta/. (1987) virtuallythe entire sedimentpenetrability Marine EcologyProgress Series 85: 1- populationof waderswintering in East Africaleaves the 8. area; however, this is not the case on Fuerteventura or the Nehls, G. & Tiedmann, R. 1993. What determines the densitiesof Banc D'Arguinon the adjacent West Africancoast (Van feedingbirds on tidalflats? A case studyon DunlinCalidris Dijk et al. 1990). alpina,in the Wadden Sea. NetherlandsJournal of Sea Research31 (4): 375-384. As regardshabitat use, the seasonaldifferences are Pierstoa,T. 1986. Coastalwaders on three CanaryIslands in noteworthy.In winter,maximum values of abundance March-April1986. WaderStudy Group Bulletin 48: 19-20. and richnesswere registeredon hard substrates, Pierstoa, T., Beintema, A.J., Davidson, NC., OAG Munster & especiallyintertidal lava platforms,whilst in summerthe Pienkowski,MW. 1987. Wader migrationsystems in the oppositeoccurred, waders preferring sites with a EastAtlantic. WaderStudy Group Bulletin 49, Supplement. predominanceof soft substrates. IWRB SpecialPublication 7: 35-56. Piersma,T., Klaassen,M, Bruggemann,J.H., Blomert,A.M., Gueye, Finally,as regardsthe age of the birds,for the majorityof A., Ntiamoa-Baidu,Y. & Van Brederode,N. 1990. Seasonal species,individuals were in freshfirst winter or juvenile timingof the springdeparture of wadersfrom the Banc plumagewIn particular,for Grey Plover,Bar-tailed Godwit D'Arguin, Mauritania.Ardea 78(1 ): 123-134. Limosalapponica and Sanderlingno individualswere observedin breedingplumage. This seemsto indicate Recher,H.F. 1966. Someaspects of the ecologyof migrant that immaturebirds spend their first summer outside their shorebirds.Ecology 47(3): 393-407. breedingareas, usuallyin theirwinter quarters (Cramp & Smit, C.J. & Piersma, T. 1989. Numbers, midwinterdistributions Simmons 1983). Thus, it is essentialthat summering and migrationof waderpopulations using the EastAtlantic areas for wadersare conserved,since they harboura Flyway. In: H. Boyd& J.-Y. Pirot(eds.) Flywaysand reserve significantpercentage of first-yearbirds whose importance networksfor waterbirds:24-63. IWRB SpecialPublication 9, lies in their value for futuregenerations of waders. Slimbridge. Summers, R.W., Underhill, L.G., Pearson, D.J. & Scott, D.A. 1987. Wader migrationsystem in southernand easternAfrica and westernAsia. WaderStudy Group Bulletin49, Suppl./IWRB ACKNOWLEDGEMENTS Special Publication7: 15-34.

N.J. Abreu and R. Linares collaborated in the fieldwork. Van Dijk,A., de Roder,F.E., Marteijn,E.C.L & Spiekman,H. 1990. Summeringwaders on the BancD'Arguin, Mauritania: a census in June 1988. Ardea 78: 145-156.

REFERENCES Wolff,W.J. 1969. Distributionof non-breedingwaders in an estuarine area in relation to the distribution of their food organisms.Ardea 57 (1-2): 2-27. Cabo,J.M. & S•nchez,J.M. 1985. Descripci(Snde la comunidadde lim[colasde la Mar Chica(Marruecos). Alytes II1: 89-95. Zwarts,L. & Pierstoa,T. 1990. How importantis the BancD'Arguin, Mauritania,as a temporarystaging area forwaders in spring? Dominguez,J. 1989. Distribuci(Sn delim[colas enzon•as de Ardea 78(1): 113-121. alimentaciOny reposaderos de pleamarde la R[ade Ortigueira. Thalassas 7: 31-38.

Emmerson,K.W. 1988. Estudiobase para la catalogacidny valoracidnecoldgica de las principales areas del litoral canario para un futuroprograma de conservacidn.Vol. 1 & 2. Ornistudio S.L.

Ens,B, Duiven,P., Smit,C.J. & VanSpanje, T.M. 1990. Spring migrationof turnstonesfrom the BancD'Arguin in Mauritania