Summering Coastal Waders on Fuerteventura, Canary Islands, Spain
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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 number of birds),species richness (total number of species),length The Canary Islandsare situatedon the western extreme of of coastalarea and substratetype. The latterwere the East Atlantic Flyway. 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