Informationabout the habitatuse of salinesand pondsby winteringwaders in CadizBay, southwest Spain

A. Perez-Hurtado & F. Hortas

Perez-Hurtado,A. & Hortas,F. 1991. Informationabout the habitat use of salinesand fish bywintering waders in CadizBay, southwest Spain. WaderStudy Group Bull. 66: 48-53.

CadizBay, recently declared as a NaturalPark, is an importantarea for wintering waders in Spain. In the lastfew years and salines in Cadiz Bay have been claimed for human activities with adverseimpacts on their shorebird populations. Thus, the importance to shorebirdsof thesalines andfish ponds adjacent to theBay could be increasingif they are usedas alternativefeeding areas. In generalthe birds used the salines and fish ponds both for feeding and roosting: some 66% of wadersin salinesat lowtide were feeding. However,not all the birdsused the differenthabitats in thesame way or at thesame state of tide. Someimplications of the usemade by waders of these areasto theirenergetic requirements, morphological adaptations and prey availability are discussed.

A. Perez-Hurtado& F. Hodas,Laboratorio de BiologiaMarina, Apto. de Fisiologiay Biologia Animal,Facultad de Biologia,Universidad de Sevilla,Aptdo 1095, E-41080, Spain.

INTRODUCTION

Thewetlands of CadizBay (between 36ø23'N, 6ø08'W and 36ø37'N,6ø15'W, southwest Spain) extend over 18,000 ha, sall•es la tapa andinclude many different and productivehabitats; intertidal mudflats,salines, fish ponds, and semi-natural salt marshes(Figure 1). Thesesupport a largenumber of winter- ingwaders (30,000 birds approximately, Alberto et al. 1987). Dueto the strategicgeographic position of the Bayon the fishpond EastAtlantic Flyway it is possiblyan importantstaging area for Study area migratingwaders.

Nonetheless,only a fewgeneral studies have been under- takenin relationto thewader populations of CadizBay and theirlinks with other Iberian (Alberto & Velasco 1988;Dugan 1980; Hortas 1990; Smit in press).There has also been little work on the use that some waders make of the feedinghabitats here (Perez-Hurtado & Garcia1990; Perez -Hurtado& Hortas1990).

Although10,000 ha of CadizBay have recently been declared a NaturalPark, a greatnumber of changeshave taken place overthe last20 yearsof humanactivity in thesalines and mudflats.A highproportion of salines(62% of theoriginal area) havebeen deserted or drainedand, in somecases, the pondshave been filled to allowhouse building. Other ponds Figure1. Locationof CadizBay in the EastAtlantic Flyway (inset) and the havebeen deepened and transformed into fish ponds (25% of distributionof differenthabitats in the Bay. The mapalso shows the study thearea). Thesechanges clearly affect the waders using areasselected: 'Salinas la Tapa'and the fishpond study area. these areas. Keyto habitattypes

The humanmanagement regime in the remaining fish ponds Salinas alsostrongly affects birds. In general,ponds are emptied in • •lsnponds ":• lost salinas ,Cities

48 tonnes and holds about 10% of the total number of waders in I•IONTH•-qTATU9 LOWTIDE I IllOHTIDE the Bay. Forcensusing and studying bird distribution, we also made observations on the mud beside Guadalete River close to thesesalines. Finally, we selecteda representativefish pondand area close to PuertoReal village (Figure 1 ). - •R• WA•• • ..... ;. •:-,,..[ ,...... " ..... * ...... 1 • T• i FE•U•Y I In thesehabitats, data were collected in goodweather conditionsat lowtide, in Decemberor earlyJanuary, when winteringnumbers are morestable in CadizBay. We also collectedqualitative information about habitat use, at hightide, •TI• inthe fishpond area selected.

To understandthe habitatsused by differentwaders, we recordedthe locationsof thoseobserved on habitatmaps. We identifiedfour habitat categories: mudflats, walls (with and Figure2. Annualmanagement regime of the fishponds in termsof water withoutvegetation) and five sub-categories of ponds: level,season and tidal cycle. Type0 = Wet groundbut no water Type1 = Shallowwater < 3 cm Octoberor Novemberto collectfish; after, this, pond sluices Type2 = Waterlevel 3-11 cm areopened and sea-water can move in and out with the tide. Type3 = Waterlevel 11-20 cm Duringthis period, from November to February,a large Type4 = Waterlevel > 20 cm amountof marinenutrients enter the pondswith the tide, perhapsaugmenting the production of preybiomass. From

Februaryto thefollowing October, the sluices of the pondare LEVEL 0 LEVEL 1 closedto allowfish cultivation (Figure 2).

The mudflatshave been adapted for the culture of thebivalve molluscVenerupis semidecussata in twoways that reduce preyavailability to wadersconsiderably. The mud is removed andmixed with gravel, creating a newsurface layer to a depth of approximately12 cm. In somecases, nets are alsoplaced on the surface.

We thinkthat the importanceto shorebirdsof the salinesand LEVEL 2 LEVEL fishpond habitats comes from their use as alternativefeeding groundswhich may help waders to obtaintheir daily energy requirementswhen feeding opportunities are limitedon the mudflats.Given the changesin the habitatsthat have taken place,it isvery important to knowhow bird numbers and distributionhave changed in thearea over recent years and how waders use these habitats. The aim of this work was thusto investigatethe useby birds of twocontrasting habitats in CadizBay: a modernsalina and a representativefish pond (Figure1). Someimplications related to tidalcycle, morpho- logicaladaptations and energetic requirements are also Figure3. Fourcategories for estimationof waterlevel in pondsin relationto discussed. the Black-wingedStilt leg.

Type0 = Wet groundbut no water Type1 = Shallowwater < 3 cm METHODS Type2 = Waterlevel 3-11 cm Type3 = Waterlevel 11-20 cm

The data were collected each winter in a modern salina from 1987,and ina representativemarine culture (fish pond) area from 1988. To make the observations we used two 15 x 60 The habitat and water level were recorded for each bird telescopesand a carto movethrough the area. observed.To estimatewater level we useda scoringsystem basedon the mean'leg level' of birdsfeeding in the pond, We selectedone of thetypical modern salines in the Bay. The dividedinto four categories (Figure 2). Birdactivity was 'Salinasla Tapa'has a highsalt production, of about40,000 scoredas feedingor notfeeding.

49 Table1. Habitatpreferences offeeding wading birds at lowtide in 'Salinas la Tapa' (S) and the mudflats of theGuadalete River (M) in Cadiz Bay. The estimated numbersare basedon peakcounts from the Decemberor Januarycensus.

Winter 1987/88 Winter 1988/89 Winter 1989/90 Winter 1990/91 M S %(M) %(S) M S %(M) %(S) M S %(M)%(S) M S%(M) %(S)

Haernatopusostralegus 4 100 5 1O0 Himantopushirnantopus 6 1O0 31 1O0 42 100 20 100 Recurvirostra avosetta 197 100 1 285 3 99 69 160 30 70 1 300 3 996 Charadrius hiaticula 67 57 54 46 82 65 56 44 16 113 12 82 223 100 Charadrius alexandrinus 151 172 47 53 140 134 52 48 103 289 26 74 434 58 88 12 Pluvialissquatarola 16 29 36 64 64 67 49 51 36 91 28 72 50 89 36 64 Calidris alba 6 4 60 40 19 100 5 10 33 67 55 30 65 35 Calidris minuta 2 35 5 95 21 100 15 100 8 21 28 72 Calidds ferruginea 1 28 3 97 15 10 60 40 4 4 50 50 3 1O0 Calidrisalpina 40 505 7 93 399 411 49 51 247 661 27 73 1287 98 93 7 L/rnosa lirnosa 395 1O0 1 146 7 99 120 100 146 1O0 Lirnosalapponica 1 1O0 21 1 96 4 2 1O0 Tringa totanus 65 150 31 68 175 54 76 24 52 106 33 67 230 99 70 30 Arenaria interpres 1 1O0 6 3 67 33 2 1 67 33 6 100

TOTAL WADERS 348 1580 927 1228 541 1614 2299 861

HABITAT USE (%) 18 82 43 57 25 75 73 27

RESULTS AND DISCUSSION KentishPlover Charadrius alexandrinus, Dunlin Calidris alpina,and Sanderling Calidris alba) fed on mudflatsat low The importanceof thesalines and fish ponds for feeding tide(Table 1) butin the salinesand fish ponds for the restof variesgreatly between species. In 'Salinasla Tapa',Oyster- theday. Rufino(1984) showed similar patterns to thosefound catcherHaematopus ostralegus, Bar-tailed Godwit Lirnosa here for KentishPlover, Bar-tailed Godwitand Black-tailed lapponica,Grey Plover Pluvialis squatarola and Turnstone Godwitin the Algarye of SouthPortugal. In generalthe Arenariainterpres, mainly concentrated their feeding on the salinesare used at alltimes of dayby waders for feeding and mudflatsat lowtide. Otherssuch as Black-wingedStilt forroosting. They are alsoused at night(Rufino et al. 1984; Hirnantopushirnantopus, Black-tailed Godwit Lirnosa limosa, Batty1988). LittleStint Calidrisminuta and AvocetRecurvirostra avosetta, fednearly exclusively inthe salines and fish ponds (Table 1) Theproportion of birdsin 'Salinas la Tapa'which were feeding wasabout 66% at lowwater (Table 2 & 4). The habitats Severalsmall species (Ringed Plover Charadrius hiaticula, selectedmost frequently were ponds with a wetsubstrate, but

Table2. Numbersof birdsfeeding and not feeding at lowtide in 'Salinasla Tapa'.

January1989 January1990 January1991 Feeding Not Feeding Not Feeding Not feeding feeding feeding

Haernatopusostralegus H/mantopushimantopus 66 2 10 6 3 17 Recurviros tra a vos etta 65 125 4 125 1 275 Charadrius hiaticula , 43 61 95 26 Charadrius alexandrinus 1O0 269 153 56 58 Pluvialissquatarola 98 8 76 2 87 Calidris alba 6 3 10 30 Calidris rninuta 17 13 21 Calidrisferruginea 5 2 Calidrisalpina 527 795 76 22 L/mosa limosa 159 81 27 119 L/mosa lapponica Tringa totanus 125 4 70 4 89 4 Arenaria interpres 2

TOTAL WADERS 1115 562 1241 293 307 524

ACTIVITY PERCENTAGES 66.5 33.5 80.9 19.1 37.0 63.0

50 Table3. Habitattypes selected bywaders atlow tide in 'Salinas laTapa'. WWV --Saline walls with vegetation, WNV = Salinewalls with no vegetation, P0-1 = Pondtypes 0 & 1 (water< 3 cm),P2-3 = Pondtypes 2 & 3 (water3-20 cm), P4 = Pondtype 4 (water> 20 cm). January1989 January1990 January1991 WWVWNV P0-1 P2-3 P4 WWVWNV P0-1 P2-3 P4 WWVWNVP0-1 P2-3 P4

Haematopusostralegus Himantopushimantopus 2 66 6 10 8 Recurvirostraavosetta 190 125 4 35 265 Charadriushiaticula 104 2 119 Charadriusalexandrinus 1 11 353 4 209 58 Pluvialissquatarola 26 41 31 30 54 16 39 34 Calidrisalba 3 1 10 25 5 Calidrisminuta 17 13 20 1 Calidrisferruginea 5 2 Calidrisalpina 527 795 15 35 48 Limosalimosa 159 81 146 Limosalapponica Tdngatotanus 100 29 69 14 2 7 90 Arenariainterpres 2 TOTALWADERS 27 55 1142 453 6 157 1352 28 76 184 601

Table4. Habitatuse at lowtide, in 'Salinasla Tapa'and muds of Guadalete river.

January1989 January1990 January 1991

ACTIVITY Number of total Numbers of total Numbers of total waders waders waders

Feeding on mud 927 541 2299 Feeding on salines 1115 1241 307 Roosting on salines 562 293 524

TOTAL WADERS 2604 2075 3130

nosurface water, and ponds with shallow water (Table 3), mudflatsand at hightide roosted on the walls (see Tables 5 & wherethe prey (Hydrobia ulvae, Chironomid larvae and 6). However,small species such as RingedPlover, Kentish nymphs,Polychaete worms and Ephidridae) would be more Ploverand Dunlin, fed throughout the day on mudor in the availablethan in deeperponds (pers. obs.). pondsat lowwater, and in ponds at highwater. They mainly usedponds with wet substrate or shallow water. Small The lastfour tables show a differenthabitat use in January speciesfed for a greaterpart of the day and so depended 1991. Inthat year fewer waders fed in the salines while a moston the hightide feeding areas provided by the salines greaternumber fed on the mud. This difference was particu- andfish ponds. larlyobvious inthe smaller species; Kentish Plover, Ringed Plover,Dunlin, Sanderling and Curlew Sandpiper. These Theponds with water depth of 1-20 cmwere primarily used speciespreferentially used mud (Table 1), while in previous bythe long-legged species, such as Black-wingedStilt, wintersthey also used salines, feeding on pond type 0-1 Avocetand Black-tailed Godwit. Ponds with greater depth of (Table3). Thereason for this change could be related to a waterwere used by Avocet only. Thus the sameponds can delayin the normal management activities ofthe ponds in be u,;edfor feeding by different species depending on water 1991;the pond sluices were not yet opened in January and so level,this being determined by humanaction and morphologi- thewater level of the pondsexceeded a depthof 20 cm. caladaptations such as billand leg length.

Theuse made of thesalines and fish ponds varied according Onthe other hand, some species with very similar morphol- tothe body size of the bird. Large species, such as Grey ogy,like Black- and Bar-tailed Godwits did not feed in the Plover,which take larger prey fed only at lowtide on the samehabitats in CadizBay (Table 5 & 6). Black-tailed

51 Table5. Distributionoffeeding (F) and roosting (R) waders at low tide, in different habitats ofa fishpond in Cadiz Bay (habitat codes as Table 3) inJanuary 1991. WWV WNV P0-1 P2-3 Mud

Himantopushimantopus 29 R 40 F 38 F Recurvirostra avosetta 10 F 1 Charadrius hiaticula 28 F 70 Charadrius alexandrinus 11 F 4 Pluvialissquatarola 8 R 76 Calidris alba Calidris minuta 6 F Calidrisalpina 25O Limosa limosa 2 F 43 F Limosa lapponica 134 Trfnga totar.us 79 F 8 Actitishypoleucos 9 F Arenariainterpres 5

TOTALWADERS 29 8 139 91 548 Table6. Distributionoffeeding (F) and roosting (R) waders at high tide, in different habitats ofa fishpond in Cadiz Bay (habitat codes as Table 3) in January1991.

WWV WNV P0-1 P2-3 Mud Himantopushimantopus 15 R 1 F 25 F Recurvirostra avosetta 8 F Charadr/us hiaticula 53 R 20 F Charadrius alexandrinus 5 R 10 F Pluvialissquatarola 112 R Calidris minuta 7 F Calidrisalpina 28 R 132 F Limosa limosa 8 F 31 F Limosa lapponic• Trfnga totan.•s 33 F 12 F Act•*ishypoleucos 7 F Arenaria i,3teipres 4 R

TOTAL WADERS 15 202 218 76

Godwitused pond Type I and2 throughoutthe day, while ACKNOWLEDGEMENTS Bar-tailedGodwit fed only on the mudflatsat lowtide. Wewish to thank all those who helped in various ways to do Thecontinuing loss of mudflatareas in CadizBay increases thiswork. Ourspecial thanks to J.D. Goss-Custardand theimportance ofthe salines and fish ponds as alternative F.J.Garcia for their helpful comments, suggestions and feedingareas. The problemof mudflatloss is mostacute for encouragement.We thank B. Ensfor his help with the thesmall species (Kentish and Ringed Plovers, Sanderling, English:any remaining errors are entirely our own. We also Dunlinand Curlew Sandpiper) which need to feedthroughout aregrateful with 'Union Salinera de EspanaS.A.' and Sal- theday to obtainall their daily energy requirements. vadorAlgarin from C.U.P.I.M.A.R.

Thedifferent morphological adaptations and energetic requirementsofthe variousspecies allow them to feedat a REFERENCES rangeof differentwater levels. However,water level is most criticalto smallerwaders, because at hightide they can only Alberto,L.J., Solis, F. & Hortas,F. 1987.Importancia para la feedin pondswith no or shallowwater. It isvery important to invernadade Limicolasde las zonas h8medas de la Bahia de knowhow different fish pond management regimes could Cadiz.Coastal wetlands symposium, Sevilla 7-8 May,1987. affect the food intake rates of waders and how different waderswith different diets, morphological adaptations and Alberto,L.J. & Velasco,T. 1988. Limicolas invernantes en energeticsrequirements use these habitats, and the relative Espa•a. In:Monografias de la S.E.O.1, Invemadade aves importanceof thesedifferent habitats to the birds.These are en la PeninsulaIberica. Ed. byJ.L. Telleria theaims of our continuing field work. Batty,L. 1988.Seasonal and diurnal variations inthe feeding

52 intensityof wadersin the Ria Formosa,Portugal. Wader theW.S.G. Annual Meeting, Lido degli Estensi, Italy, 5-8 StudyGroup Bull. 54:9-10. October 1990.

Dugan,P.J. 1980. Springcounts of wadersat coastal Perez-Hurtado,A. & Hortas,F. 1990. Some information wetlandsin SouthernSpain. WaderStudy Group Bull. 30: aboutthe use of salinesand marine cultures by wintering 14-16. shorebirdsin theCadiz Bay, Southern Spain.

Hortas,F. 1990. Phenologyof wadersin 'Salinasla Tapa', Rufino,R., Araujo,A., Pina,J. P. & Miranda,P.S. 1984. The CadizBay, SouthwestSpain. Communication presented at useof Salinesby waders in the Algarye, South Portugal. theW.S.G. Annual Meeting, Lido degli Estensi, Italy, 5-8 WaderStudy Group Bull. 42:41-42. October 1990. Smit,C. J. in press.The importanceof Iberianwetlands for Perez-Hurtado,A. & Garcia,F.J. 1990. Informationabout the waders.J. CastroviejoEd. Proc.IWRB Symp. Sta. Maria de dietof RedshankTringa totanus, feeding in traditional salines la Rabid,Spain, 1983. of CadizBay, Southwest Spain. Communication presented at

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