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The wader communities of a saline and an intertidal site on the ,

LeslieBatty

Batty,L. 1992. Thewader communities of a salineand an intertidalsite on the RiaFormosa, Portugal.Wader Study Group Bull 66: 66-72.

Comparisonsare madebetween the two sites in relationto the permanencetime of species, seasonalvariations in abundance and species composition.

LeslieBatty, Unidade de Ci•nciase Tecnologiasdos Recursos Aquaticos, Universidade do ,Campus de Gambelas,8000 Faro, Portugal.

INTRODUCTION Rufinoet al. (1984)gave the following values for the percen- tageof thetotal wader population feeding and/or resting on The RiaFormosa is a tidallagoon system along the eastern thesalines at hightide: January 36%, February24% and sectionof the southcoast of Portugal.It stretchesabout 60 March29%. Theyalso pointed out the variationbetween kmfrom Ancao/(36ø58'N, 8ø02'W), 20 km speciesin the useof salines- Black-tailedGodwit Limosa westof Faro,eastwards to CacelaJMantaRota (37ø03'N, limosa,for example,being almost exclusive to salineseven at 7ø32'W)east of (Figure 1 ). Thefirst published count of lowtide, Kentish Plover Charadrius alexandrinus roosting wadersin the Ria Formosawas madein January1975 by therein considerable numbers but also using the Riafor CEMPA(the ornithological section of the ServicoNacional de feeding,and Bar-tailed Godwit Limosa lapponica not using Parques,Reservas e a Conservacaoda Natureza).This the salines at all. gavea totalof 12,775birds of 20 species(Rufino 1978), and thefollowing years - 1976and 1977 - producedcounts of However,no publishedinformation exists on wadernumbers 20,068and 21,383 waders respectively. During the period andspecies composition during the complete annual cycle on 1975-78 the averageJanuary counts on the principalPor- the RiaFormosa, although Rufino & Araujo(1987) described tugueseestuaries and lagoon systems were as follows:mejo seasonal variations between the end of November and the estuary54,560, Ria Formosa18,800, Ria de Aveiro13,460, endof May. Thispaper presents information on the complete Sadoestuary 12,570 (Rufino 1978). The mostrecent pub- annualcycle on a salineand an intertidalsite, and makes lishedcount, for January 1988, was of 17,883waders of 24 comparisonswith the work of Rufinoet al. (1984)and of species(Rufino 1988), although the coverage was not Rufino& Araujo(1987), as wellas withthe salines of the complete.The Ria Formosaalso provides habitat for large Camargue,southern (Britton & Johnson1987) and the numbersof ducks,coots, egrets, storks, gulls, terns and other lagoonsof Andalusia,southern (Amat 1984). aquaticspecies which breed and/or winter there. STUDY SITES AND METHODS Of the8,350 ha lagoonsystem, the following are theareas of the majoraquatic habitats from Teixeira & Alvim(1978): Thestudy saline was a largeevaporation tank in the south-centralsection of the salinecomplex at Ludo,near Saltmarshes,mudflats and sandbanks 4,800 ha Faro(Figure 2). Thiswas chosen because of itseasy access Channels,creeks and bottoms 3,550 ha andthe fact that it holdswaders throughout the year. This Salines for extraction of -salt 900 ha salineis 230 m by 190 m (4.37ha.). Thesaline is subdivided Aquaculturetanks 200 ha byinternal ridges into eight rectangular sections, although mostof the ridgeshave become so erodedthat they are Rufinoet aL (1984)and Bijlsma et al. (1985)showed the underwater for mostof thesummer, and only start to appear importanceof thesalines of the Riaas feedingan/or roosting as thewater level drops in Octoberowing to drainage and areasfor largenumbers of waders.They also showed that evaporation.The one main ridge which remains reaches a thereare markedmovements of somespecies between the heightof aboutone metre, and it andsurrounding banks have salinesand intertidal areas, whilst other species generally a sparsecovering of halophyticvegetation. feed either on the salines or on the intertidalareas. Theinvertebrate fauna of thesaline is dominated by the brine • SPAIN

RIA FORMO

The location of the study sites at Ludo Key: [] = studysa/tna; [] = intertidalsite; R = river (Ribeira de Sao Laurenco); SM = saltmarshes: SB = sand bar (Prala de Faro},

Scale approxm)ately 1 . 18,000

F,gure1 The locationof the Ria Formosaand the Ludostudy area. Figure2 The locationof the studysites at Ludo. shrimpArtemia, larvae, pupae and adult insects of the familiesEphydridae and Chironomidae,and beetlesof the Boththese study sites are obviouslysmall in relationto the familyHydrophilidae. habitatsthey represent and it isdifficult to sayto whatextent theyare typical. However, they presented a practicalsize for Thesaline is usuallyfilled with sea water during April, and detailedstudies (Batty 1991) whose results should be ableto remainsfull, with some slight fluctuations, until the salt serveas a referencepoint for further work. extractionprocess finishes during October. Buring October thewater level begins to fallthrough evaporation and drain- Countswere made at thesaline and the intertidal area up to age,and is diluted by autumn and winter rains. The salinityof fourtimes a month,as nearto theneap and spring tides as thewater varies throughout the cycle from about 8ø/øø to over possible,from February 1987 to April1989. Countswere 112ø/oo,being lowest in winterand early spring because of madeon the saline for up to 4 hoursuntil the publishedtime rainfall,and highestin summerand early autumn because of of highwater, and on the intertidalsite for up to 4+ hoursfrom evaporation. the publishedtime of lowwater. In thisway the periodsof maximum numbers in each site were covered. In total 337 The intertidalsite is an area of 6 ha, about380 m due south countswere made on the intertidalsite during 74 visits,and ofthe saline,bounded on itsnorthern side by a seawall and a 380counts were made on the saline during 94 visits,covering thinstrip of saltmarsh,and on itssouthern and western sides a totalof 132different days. bysaltmarsh. It emptiesand fills with tidal water from a channelwhich runs in fromthe easternend, and the substrate Various authors have reviewed mudflat bird census methods is moreor lessentirely soft mud. It waschosen as a study (e.g.Storer 1951; Jeh11963; Recher 1966; Gerstenberg sitebecause of itsproximity to thesaline complex, its 1972)and, whilst some workers tend to aimfor a censusof well-defined boundaries and ease of access and observation. the maximumnumber of birdspresent, others aim for an The invertebratefauna is dominatedby polychaeteworms, averagenumber of birdsusing the areaat differenttimes of especiallyof the genusNereis and Heteromastus, but there thetidal cycle. Recher(1966) considered that an accurate arealso molluscs - Scrobicularia plana and Hydrobia ulvae- assessmentof speciescomposition is best made on a falling andcrustaceans - Ucatangeri, Carcinas maenas and tideafter 30-60% ofthe tidal mudflat has been exposed, Cyathuracarinata. which,according to Storer(1951 ), isthe period of maximum

67 numberson a mudflat.However, for reasonsrelated to other (1987)(in the caseof the Andalusianlagoons). studiesundertaken during the course of the project (Batty 1991), countswere made during rising tides. Seasonalvariations in thenumbers of eachspecies

Prater(1981) suggested that there are "almostinnumerable RESULTS AND DISCUSSION possibilities"in presenting monthly variations in birdnumbers, butconcluded that the average peak count indicates average Permanencetime of species maximumusage of thesite. Thiswas used in this study to analysemonthly variations in the numbersof eachspecies. Duringthe annual cycle, different species occurred on the Foreach species the maximumnumber recorded on each studysites over different periods depending on their migration visitin eachmonth of the yearwas taken and the meanvalue andbreeding phenologles. The numberof monthsin which a calculated,and full details are givenin Batty(1991 ). Table2 speciesmay be present in an area has been called its indicatesthe seasons in which each species showed peak 'permanencetime' (Amat1984), and Table 1 showsthe numbers on each site. permanencetime of waders on the study sites during the annualcycle. It shouldbe notedthat this permanence time Of 13 speciesshowing peaks on oneof the studysites in refersto thespecies and not to individuals,which may be winter,and three showing peaks in spring, all except Green- presentfor muchshorter periods. shankTringa nebularia were so listedby Rufino& Araujo (1987),although they gave no information for Golden Plover Thereare interesting differences between these results and Pluvialisapricaria, Lapwing and Snipe Gallinago gallinago thoseof Amat (1984) for Andalusian lagoons, and Britton & whichwere winter visitors to the saline,showing a peakin Johnson(1987) for Camargue salines. Amat (1984) found no December/January.Portuguese ringing recoveries (Candeias waderspecies occurred for a durationof 11-12 monthsof the & Castro1982) of GoldenPlovers ringed as migrantsor year,and only two species (Kentish Plover and Lapwing winteringbirds in Holland, suggest that the birds at Ludowere Vanellusvanellus) occurred for a durationof 9-10 months fromthe populationbreeding in Fenno-Sandia/northern whereasLapwing are only winter visitors on the RiaFormosa. Russia(Cramp & Simmons1983), whilst most Lapwing may Absentfrom the Camarguesalines in winterwere Black havebeen from the centralEuropean population of West -wingedStilt Himantopus himantopus and Kentish Plover, ,Holland and Belgium (Candeias & Castro1982), a whichoccur only as breedingsummer visitors. These Januarypeak indicating the importanceof hardweather differencesare probably due to geographicalposition (in the movementsin bringingLapwings to the Algarve. caseof the Camargue)and the generaldifference between salinesand naturalsalt lakes referred to by Britton& Johnson Althoughthere is a smallbreeding population of Avocet

Table1. Permanencetime of waders on the study sites during the yearly cycle (s = saline;i = intedidalsite).

Number of months 1-2 3-4 5-6 7-8 9-10 11-12 Himantopushimantopus s Recurvirostra avosetta Charadrius hiaticula C. alexandrinus Pluvialisapricaria P. squatarola s Vanellus vanellus Calidris canutus s C. alba C. minutus C. ferruginea i s C. alpina Philomachuspugnax Gallinagogallinago Limosa limosa Numeniusphaeopus N. arquata Tringa etythropus T. totanus T. nebularia Actitishypoleucos Arenaria interpres

68 Winter Spring Summer Autumn Nov-Feb Mar-May Jun-Jul Aug-Oct

Himantopushimantopus s Recurvirostra avosetta s Charadrius hiaticula i s C. alexandrinus s i Pluvialisapricaria s P. squatarola i s Vane//us vaneflus s Calidris canutus s i C. alba s C. rninutus s C. ferruginea si C. alpina si Philornachuspugnax s Gallinagogallinago s Lirnosa lirnosa s i Nurneniusphaeopus i N. arquata i Tringa erythropus s T. totanus si T. nebularia s i Actitishypoleucos si Arenaria interpres s i

Table2. Seasonsof peaknumbers of eachspecies on the studysites (s = saline;i = intertidalsite).

Recurvirostraavosetta on the Ria Formosa,the peakin Rufino& Araujo(1987) described Black-tailed Godwit Limosa Novemberat Ludocoincided with the periodof post-moult !imosaas mainlya wintervisitor, but also a springmigrant in migrationof northEuropean adults from the HeligolandBight the Ria Formosa.However, a peakon the intertidalstudy site andDutch Delta (Cramp & Simmons1983; Boere & Smit inAugust/September shows that it isalso an autumnmigrant. 1983). Thepassage migrants were probably from the European population,which winters mainly in Africanorth of theequator LittleStint Calidris minutus were present in the studyarea (Cramp& Simmons1983), including many from Holland mainlyfrom September to February,with a peakon the saline (Candeias& Castro1982), whilst the wintering population in February.Many of the autumnbirds were probably mayalso include icelandic birds (Prater 1975). The peak on migratingon to Africa,and winter fluctuations in numbers the salinecoincided with return passage which occurs in (Batty1991; Rufino & Araujo1987) may have been due to February.Most birds in thestudy area usedthe saline, lateonward post-moult movements referred to byCramp & exceptduring autumn passage when the intertidalsite was Simmons(1983). also used.

Peaknumbers of DunlinCalidris alpina were reached on both Thesubstantial wintering population of KnotCalidris canutus sitesduring the winter, as confirmedalso for the Ria in indicatedin Rufino& Araujo(1987) was poorly represented generalby Rufino & Araujo(1987). Autumnmigration through onthe studysites, as thesewere away from the mainfeeding theAlgarve begins with the passageof adultsof the continen- areas. The peakon the salinewas in May,coinciding with the tal schinziirace in lateJuly. Thesecontinue on to NWAfrica peakon the Riaas a whole,as winteringbirds pass through andare followedduring August-October by the juveniles, and en routeto theirnorth-central Siberian breeding grounds the adultsand juveniles of the icelandicpopulation, the later (Dicket a11987;Rufino & Araujo1987). The peakon the arrivalsremaining to winterin the Algarve. Some alpina are intertidalsite was in September,coinciding with the autumn presentduring September-October, theadult Dunlin popula- migrationof theSiberian breeding population. Rufino & tionin the Algarvecontaining a muchhigher proportion of this Araujo(1987) assumed that the winteringpopulation on the racethan does the juvenilepopulation, and some at leastcan Riais of Nearcticorigin, although Cramp & Simmons(1983) be assumedto passon to .More arrive in the late mentionthe mostsoutherly wintering population of Nearctic autumn,to winterin the Algarve after moulting on the Wadden birdsas in westernFrance, and Kerstenet al. (1983)con- Sea and the Wash. Small numbers of arctica also seem to be cludedthat the Moroccanwintering population isof Siberian present,both as autumnpassage and as winteringbirds. The origin.it is morelikely that the Knotswintering on the Ria winteringbirds leave during March, at whichtime passage Formosaare from Siberia,and that the declinein numbers alsostarts of thosebirds which have been wintering in NW afterDecember is dueto regionalinter-estuarine movements. Africa.This passage reaches a peakin lateApril with arctica andIcelandic schinzii being a dominantelement. As Rufino& Araujo(1987) only included data for November to

69 Communitycomposition May,they attributed toother seasons all species which had mainpeaks on the study sites during summer and autumn. Black-wingedStilt Himantopus himantopus were present in The relativeabundances of the commonestspecies of waders peaknumbers on the saline in summer owing to the presence on the salineand intertidalsite throughout the year,calcu- ofadults and juveniles of thebreeding population, but were latedon the basisof the averagemonthly peak counts, are listedwith species showing a mid-winter peak by Rufino & comparedinFigure 3. Figure4 showsthe variations in Araujo(1987). A secondpeak in September may have been speciesrichness (number of species) of both sites. The most dueto migrants from northern Iberia and France (Cramp & abundantwader on bothsites was clearly Dunlin, followed by Simmons1983), and there was also a smallwintering KentishPlover, and with Redshank almost as abundantas population. KentishPlover on the intertidalsite though not on the saline. Redshankhowever, appeared to be moreabundant on some Therewere two peak periods for the Ringed Plover othersalines, especially those nearer the intertidal area and Charadriushiaticula, a main autumn peak coinciding with the duringsummer there was a tendencyfor this species to roost passageof NENearctic and NW European birds to west on saltmarshesrather than on salines. Africa(Cramp & Simmons1983), and a secondpeak from Januaryto March (shown also by Rufino & Araujo1987) Incomparison Rufino & Araujo(1987) showed that for the whichmay indicate that return migration from NW Africa starts wholeRia, Dunlinwere about four times as abundantas any inJanuary, or that there is a latewinter movement ofbirds otherspecies from the end of Novemberto earlyMarch. fromnorthern Europe. The small passage in May of African Bar-tailedGodwit was the mostabundant other species, and birdsen routeto thearctic, as shownby Rufino & Araujo KentishPlover and Redshankwere in aboutsixth and fourth (1987)was not represented onthe study sites. (a} Salina KentishPlover Charadrius alexandrinus were present on both thesaline and the intertidal study site during all months. Peak % numberson the intertidal site in August coincided with the 100 .... :...:... ß . periodof autumn migration, and there were secondary peaks --=-•'• • SW Stilt onthe saline in February (and March) during the period of '•'='•'--'=-"•'" ..... ß -'-'-'-=-=-i•::==•'"='='•"':"• Ringed P ß,,-,•. .. •• _•• •-.'i •] KentishP reoccupationofbreeding sites and spring migration and i:'= --• L Stint duringJune when large numbers of juveniles were present. 60 • - ..-'.= • Dunlin ß"• .• B'r Godwit Rufino& Araujo(1987) described Whimbrel Numenius 4.0 ',•' ß '"' "';'•:'' • •' ' • OtherRedshankspp. phaeopusashaving a a smallwintering population and a peakpassage inApril, but they missed the main peak which occurs,as indicatedon the intertidalstudy site, during return o Jan Feb Mar •.pr May Jun Jul Aug Sep Oct Nov Dec passagein July and August. Month

Autumnmigration of RedshankTringa totanus appears to (b) Intertidal site beginin July with the arrival of some adults and juveniles from northernEurope, and peak numbers were reached on the studysites in August (Rufino & Araujo (1987) gave peak

numbersfor winter). Migration continues during September Ringed P. andOctober with a largemajority of juvenilesinSeptember Kentish P. anda smallmajority ofadults in October, possibly as a result Grey Plov. ofthe onward movement ofjuveniles to NWAfrica and/or the Dunlin BT Godwit arrivalof post-moult adults. Although a few of the juveniles Redshank seemto befrom northern and Spain, the majority 4O Turnstone arefrom the countries of north-centralEurope, especially Other spp. Denmark,Germany and Holland. Most of the adults seem to befrom Spain, with a smallernumber from north-central '""•"i'.•-" •':•":"• '• .....ii• o Europe.Numbers drop to the winter level in November, when Jan Feb Mar Apr May Jun Jul Aug $ep Oct Nov Dec thepopulation ispresumably made up of a mixtureofSpanish Month andnorth-central European birds. There is a smallreturn passageinFebruary-April, peaking inMarch, only a few Rgure3. Thespecies composition ofthe wader communities ona) the saline andb) the intertidal site dudng the annual cycle, based on average monthly remaininguntil June. peakcounts. (BW Stilt = Black-wingedStilt; Ringed P. = RingedPlover; KentishP. = KentishPlover; Grey Plov. = GreyPlover; L Stint= LittleStint; BT Godwit= Black-tailedGodwit).

7O Europeanestuaries. However, a veryhigh proportion of the Riais occupied by a "patchwork"of saltmarshes and creeks, Number of Species 16 withfew areas of extensivemud- or sand-flats. However, calculationsusing data on the intertidalareas from Teizeira &

141 Alvim(1978) and on winterwader numbers from Rufino et al (1984)gave densities of 5.6-8.6birds ha-• representinga

12 moderateto highdensity in relationto averagewinter densi- tiesin intertidalareas in Britain(Batty 1991 ). Considering

1o thosebirds which use the salinesfor feeding or roosting duringat leastthe highwater period, figures from Rufino et al.

8 (1984)of 6,426waders in January, on 900 haof salines,give an averagedensity on the salines of 7.14 birdsha -1- However,a totaldensity of 106 birdsha-• wasreached on the 6 studysaline in January and a feedingdensity of 79.6 birds ha-• inFebruary. On the intertidalstudy site the densitywas 4 upto 30.5 birdsha -1 andthe highestdensity of 41.7 birds ha-• was reachedin August.

Althoughthe construction of salines has been considered Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec detrimentalto waders and other birdsof coastalwetlands, in removingintertidal feeding areas (Smit et al. 1987),those on Month the Ria Formosamay have improved the areafor waders and

Intertidal Site [] Salina otheraquatic species, as themajority of salineshave been builton saltmarshesrather than intertidal areas. Theyhave increased the area of shallow water and mud available for Rgure4. Variationsinthe species richness (number of species) of the wader feeding,supplied supplementary high-water feeding areas for communitiesof bothsites during the year, manyintertidal foraging species, and sheltered, still-water areasfor species which are usually restricted to inland places.Bar-tailed Godwit was absent from the intertidal waters,and have provided artificial banks suitable for nesting. studysite as it isa specieslargely restricted to sandysub- strateswith a goodflow (Cramp & Simmons1983), and is not foundat allon salines.In May,Dunlin and Knot comprised ACKNOWLEDGEMENTS 70%of birdspresent in the whole Ria but Knot was absent from the intertidal sites. I am gratefulto ArqtoNuno Lecoq, Director of the Parque Naturalda Ria Formosa,and to Sr. Marcelo,manager of Notabledifferences between sites includethe abundanceof Quintade Ludo,for their permission to carryout this study at Black-wingedStilt on the salineduring summer but its Ludo. completeabsence from the intertidal site. LittleStint were alsoabsent from the intertidalstudy site (although present in otherintertidal areas. The salinewas also used by a greater REFERENCES proportionofother species, especially during spring and autumnmigration periods. These included species such as Amat,J.A. 1984. Laspoblaciones de avesacuaticas en las SanderlingCalidris alba which fed elsewhere in the Riaduring lagunasAndaluzas: composicion y diversidad durante un lowwater, and less coastal species, such as RuffPhiloma- ciclo anual. Ardeola 31:61-79. chuspugnax, for which the salines resemble inland waters whichare a morefavoured habitat. Grey Plover Pluvialis Batty,L. 1991. Aspectsof the phenologyof waders squatarolaalso rested on the saline during May and (Charadri/)on the RiaFormosa, Portugal. Unpublished September/October,en route to and from wintering areas in M.PhilThesis, University of Wales. southernAfrica (Cramp & Simmons1983). The large increase in relative abundance of Kentish Plover in June is a Bijlsma,R.G., Meininger, P.L., Rekers, M., de Roder,F.E., combinedresult of the presenceof juveniles from the breed- Shulting,R. & Vogel,R. 1985. Wadercounts in the Tejo ingpopulation and the seasonal decline of Dunlinand other estuarynear and in the salinasof southPortugal. species. WaderStudy Group Bull 43: 23-24.

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