Magellanic Plovers Pluvianellus socialis in southern Santa Cruz Province, Argentina
SILVIA FERRARI•, SANTIAGO IMBERTI2 & CARLOS ALBRIEU•
• UniversidadNacional de la PatagoniaAustral, Unidad Acad•mica Rœo Gallegos, Santa CruzArgentina, albrieuc@ arnet. com.ar; 2 Rivadavia 780, 9400 R/o Gallegos,Santa Cruz, Argentina,imbertis @ ar. inter. net
Ferrari, S., Imberti, S. & Albrieu, C. 2003. Magellanic PloversPluvianellus socialis in southernSanta Cruz Province,Argentina. Wader StudyGroup Bull. 101/102: 70-76.
We presentresults of targeted surveysand casual observationsof the little-known Magellanic Plover Pluvianellussocialis in southernSanta Cruz Province,Argentina, during 1998-2002. Includedare the first recordsof the speciesusing the shoresof riversduring the breedingseason and observationsof flocksof 123 and 145 on the Gallegosand Chico estuariesduring the non breedingseason. These probably represent the largestconcentrations of the speciesever recorded,and indicatethe importanceof thesesites to the species' conservation.
INTRODUCTION beaches,mudflats and salt-marshes(mainly Salicorniaam- bigua)for breeding,feeding and roosting. Also, Jehl(1975) The relationshipsof the Magellanic Plover Pluvianellus suggeststhat Magellanic Plovers prefer sheltered areas, such socialisare uncertainand it has long beenconsidered differ- as river mouthsand bays while avoidingthe exposedcoast ent and separatedfrom true ploversbecause of variousas- of the ocean. pectsof its biology,ecology and behaviour, and also because The combinedestuaries of the Gallegos and Chico are it sometimesfeeds its chicksby regurgitationfrom the crop, subjectto multiplehuman uses, being adjacent to the city of the only known caseamong waders (see Jehl 1975). R•o Gallegos(85,000 inhabitants).In comparison,the estu- It is an endemic speciesof southernPatagonia, nesting ariesof the Coyle and SantaCruz are subjectto far lessdis- during September-Februaryon the stonyshores of inland turbanceand degradationof habitat. lakesand ponds where there are alsoclay or mudpatches in Inland, the habitat surveyedcomprised mostly shallow Tierra del Fuegoand SantaCruz Province,Argentina (Hum- alkalineponds and lakes, such as Lago Argentino,that offer phreyet al. 1970, Jehl 1975). The post-breedingdispersal to the beachesof intermixed pebblesand mud, favouredby the coastof the Atlantic Oceanusually starts in March •ers. MagellanicPlovers (Jehl 1975, Plate 1). obs.),with birdsregularly moving northto Rio Negro Prov- In an attempt to clarify the movementsof the plovers ince (Gonzfilez 1996, Harris 1998) and occasionallyas far betweenthese two areas,and to investigatetheir possible use north as BuenosAires Province(Narosky et al. 1993). of other wetlandhabitats, portions of somerivers were also Jehl (1975) suggestedthat the total populationmight be surveyed,despite the fact thatthe specieshas not previously very small,probably less than 1,000 birds.It is categorized beenrecorded as usingthem (Jehl 1975). The surveythere- as "Near Threatened" (BirdLife International 2001), "Rare" fore included sections of the rivers La Leona, Penitente, (Grigera& l)beda1997) and, due to the scarcity of studies, GallegosChico, E1 Zurdo, Chico and Santa Cruz as well as it has beenrecommended as a priority casefor researchin all possiblenesting habitat along the entire length of the Patagonia(Blanco & Canevari 1995). Gallegosriver from its sourcenear the Chileanborder to the sea. STUDY AREA AND METHODS The mean temperatureof the studyarea is 7.2ø C with prevailingW-SW windsaveraging 35 km/h with gustsocca- With the aim of learning about the distributionand move- sionallyreaching 150 km/h, mainly in springand summer. ments of Magellanic Plovers, we surveyedsmall alkaline Most inland water bodieswere visitedevery monthdur- lakesand pondswhere they breed,and areason the coastto ing the breedingseason (the australspring and summer,Sep- whichthey migratein winter.We presentthe resultsof spe- tember-February),while the Gallegosand Chico estuaries cifically targetedsurveys to areaswith suitablehabitat in the were surveyedalmost year round; other estuarieswere vis- southernpart of SantaCruz Province,south of the 50øSpar- ited mainly during winter. Observationswere made from allel in Patagonia,Argentina (see Fig. 1). We also include 1998 to 2002. some additional casual observations made on other occasions. Most of the pondswere coveredby walkingthe complete On the coast of the Atlantic Ocean, the area covered in- perimeter.Due to the size of the estuaries,lakes and rivers, cludedthe tidal estuariesof the Gallegos(51ø35'S 69ø02'W), fixed pointswere usedto make the observations.It is impor- Chico (51ø41'S 69ø09'W), Coyle (50ø58'S 69ø13'W) and tant to note that due to factors such as winter weather con- Santa Cruz (50ø10'S 68ø27'W) rivers. These were targeted ditions,accessibility and funding, we were not able to visit becauseof our experienceand previousknowledge of them all of the areasduring a completeyear. Therefore,to some being visited by various wader speciesthat use the stony extent, our observationswere not systematic. • Bulletin101/102August/December 2003 70 Ferran et al Magellan•c Plovers •n southern Santa Cruz Prov•nce, Argenhna 71
Santa Cruz Province
R Chico Lago Viedma
Rio Santa Cruz La Leona ',io Santa Cruz and Lago 13 Chico Estuaries Argentin 2
Rio Coyle Estuary Rio Coyle
lO Rios Gallegos and Chile Chico Estuaries
Rio Chico
MagellanStrait References
1- Lago Argentino 2- Paso Biggieri, Rio Leona 3- Rio Gallegos, Estancia Glencross 4- Laguna de Los Escarchados 5- Estancia La Angelina 6- Rio Gallegos Estuaryand Isla Deseada 7- Rio Chico Estuary 8- Laguna Little Hill, Estancia Morro Chico 9- Rio Coyle Estuary 10- Laguna Travesia, Estancia El Roda 11- Rio Penitente, Estancia Rinc0n de los Morros
12- Unnamed Lagoon near NR 3 (4 km N Rio Coyle) Localities of Magellanic Plover in 13- Unnamed Lagoon near NR 3 (40 km S Piedra Santa Cruz Province, Argentina Buena)
Fig. 1. Map of southernSanta Cruz Province,Argentina, showing the locationssurveyed for MagellanicPlovers (numbers cross-reference w•th Table 1).
Bulletin 101/102 August/December 2003 72 Wader Study Group Bulletin
Plate 1. An adult Magellanic Plover on the shore of Lago Argentinoon 30 November 2001 (photo by Carlos Albrieu).
Plate 2. The chick found at Estancia Glencross on the Rio Gallegos on 12-13 February 2002 (Site 3, Fig. 1, Table 1' photo by Santiago Imberti).
Bulletin 101/102 A ugust/December 2003 Ferrari et aL: Magellanic Plovers in southernSanta Cruz Province Argentina 73
Plate 3. Two adultMagellanic Plovers feeding on intertidalmud on the Gallegosestuary on 3 August2002 (photoby CarlosAlbrieu)
Table 1. Countsof MagellanicPlovers at sites in southernSanta Cruz Province,Argentina, during 1998-2002. (Full: area described fullysurveyed, Partial = area describedpartially surveyed, Casual = casualrecord, no systematicsurvey, pr = pair,juv = juvenile).Numbers correspond to location of sites in Fig. 1.
1. Lago Argentino(50ø19'S, 72ø16'W) - Largelake, 90 km longand 10-25 km wide, 185 m abovesea level.Nothofagus forests in the west, arid steppein the east. Area surveyed:5 km of shorelinewith pebblesand mud,just northof El Calafate. Land used for sheep and cattle grazing in the past but mostlyfor recreationor developmenttoday. Date 25 Oct 1999 21 Oct 2000 8 Dec 2000 30 Nov 2001 22 Sept2002 Coverage Full Full Partial Partial Full Count 10 5 3 (pr & juv) 2 6
2. Paso Biggieri, Rio Leona (50ø09'S,72ø00'W) - Largeriver connecting lakes Viedma and Argentino,160 m abovesea level,shrub steppe. Land used for sheep grazing.
Date 2 Dec 2001 Coverage Casual Count I
3. Rio Gallegos,Estancia Glencross (51ø50'S, 71ø33'W) - River,330 m abovesea level;nearest standing water 10 km (2 ha. lake). Area surveyed:8 km stretchof riverwith pebbleand sandyshores. Land used for sheepand cattlegrazing.
Date 21 Mar 2001 12-13 Feb 2002 24 Mar 2002 Coverage Casual Full Full Count 2 3 (,pr& chick) 5
4. Laguna de Los Escarchados(50ø24'S, 71ø33'W) - Lake, 2.8 km long,740 m above sea level. Shoresof pebblessurrounded by bunch-grasssteppe. Area surveyed:all of the southeastshore (about 1.5 kin). Severelyovergrazed by sheep.
Date 11 Jan 1998 13 Mar 2001 7 Jan 2002 Coverage Full Full Full Count 2 I 5
5. EstanciaLa Angelina(51ø25'S, 69ø04'W) - Smalllake, 1.2 km long,40 m abovesea level.Shores of pebblessurrounded by grassland steppe. Area surveyed:entire lake. Land used for sheep grazing.
Date 10 Feb 1999 24 Oct 1999 11 Nov 2001 Coverage Full Full Full Count 4 6 (3 pt) 11 (1 juv)
Bulletin 101/102 August/December 2003 74 Wader Study Group Bullebn
Table 1 cont. Countsof MagellanicPlovers at sites in southernSanta Cruz Province,Argentina, during 1998-2002. (Full = area descnbed fullysurveyed, Partial -- area describedpartially surveyed, Casual = casualrecord, no systematicsurvey, pr = pair,juv = juvenile).Numbers correspond to location of sites in Fig. 1.
6. Rio Gallegos Estuary (51ø35'S,69ø02'W) - Extensiveestuary, 40 km long,3-8 km wide,hugely affected by tides.Extensive pebble beachesand muddyintertidal areas. Area severelyaffected by development,fishing, sheep grazing and recreationalactivities. Includes a provincialreserve, Isla Deseada, 37 ha. Area surveyed:south coast aroundPunta Loyola(2 km) and Isla Deseada. Date 23 Mar 1999 23 Jun 2002 14 Jul 2002 3 Aug 2002 Coverage Full Full Full Full Count 145' 57 44 29
* at Isla Deseada
7. Rio Chico Estuary (51ø41'S, 69ø09'W) - Merges with the previoussite (Site 6, the Rio Gallegos Estuary).Smaller but includes extensivepebble and muddyintertidal areas used by MagellanicPlovers. Also affectedby tides and slightlymodified by development, fishing,sheep grazingand recreationalactivities. Part of it is a provincialreserve. Area surveyed:southeast coast (7 km). Date 25 Apr 1999 28 Apr 1999 17 May 1999 5 May 2002 Coverage Full Full Full Full Count 15 (8 juvs) 32 123 45 (25 juvs)
8. Laguna Little Hill, Estancia Morro Chico (51ø55'S, 71ø19'W) - Lake, 1.7 km long, 0.6 km wide, with a smaller lake usuallycon- nected,0.5 km by 0.5 km, 190 m above sea level. Grasslandsteppe, pebble and clay shores.Area surveyed:the whole of the small lake and the south shore of the larger one. Land used for sheep grazing.
Date 31 Mar 1999 3 Oct 2001 Coverage Casual Full Count 17' 3 (pr & juv) * P. Sturzenbaumpers. comm.
9. Rio Coyle Estuary (51ø55'S,71ø19'W) - Extensivetidal estuary,20 km long,2-3 km wide. Extensivepebble beachesand muddy intertidalareas. Area used for fishing,sheep grazing and recreationalactivities. Area surveyed:5 km of the southwestshore.
Date 24 Apr 1999 13 Jun 1999 Coverage Casual Full Count 1 5
10. LagunaTravesia, EstanciaEl Roda (51ø21 'S, 71ø48'W) - Largelake, 3 km long,2.5 wide,450 m abovesea level.Grassland steppe, pebble and clay shores. Area surveyed: north shore. Land used for sheep grazing.
Date 1 Jan 2000 Coverage Full Count 2
11. Rio Penitente,Estancia Rinc6n de los Morros (51ø55'S,71 ø30'W) - Smallerriver, tributary of the Gallegos,340 m abovesea level Grasslandsteppe, pebble shores. Area surveyed:6 km. Land used for sheep and cattlegrazing.
Date 14 Feb 2000 20 Jan 2002 Coverage Partial Full Count 2 2
12. Unnamed Lake near National Road 3, 4 km north of Rio Coyle (51ø04'S,69ø32'W) - Small lake, 0.6 km long, 150 m abovesea level.Shores of pebblesand clay surroundedby shrubsteppe. Area surveyed:entire lake. Land usedfor sheepgrazing.
Date 6 Dec 2000 Coverage F Count 4 (2 juvs)
13. Unnamed Lake near National Road 3, 40 km south of Piedra Buena (50ø20'S,69ø12'W) - About2-3 km long, 250 m above sea level.Shores of pebblesand clay surroundedby shrubsteppe. Area surveyed:1.5 km of east coast.Land usedfor sheepgrazing
Date 2 Dec 2002 16 Dec 2002 Coverage Partial Full Count 7 7
Bulletin 101/102 August/December 2003 Ferrari et al Magellamc Plovers •n southern Santa Cruz Prov•nce, Argenhna 75
O Inland lakes x Datesjuveniles seen l O Rivers ß Estuaries 160 +Dates chicksseen X X >X<; +
140
120 -
100
80-
60-
40-
20 o ß o o 0 o o--e 01 -Jul 30-Aug 29-Oct 28-Dec 26-Feb 27-Apr 26-Jun
Fig. 2. Counts of Magellanic Plovers in Santa Cruz Province, Argentina, during 1998-2002 plotted separately for the three different habitats occupied (lakes, rivers and estuaries) against the annual cycle.
On the breedinggrounds, all birds were agedas adultsor theseflocks may haveincluded many of the samebirds, they juvenileson the basisthat juveniles have white edgesto their representabout 14% of the estimatedworld populationof wing coverts(lacking in adults)and yellowish legs as op- 1,000 (Jehl 1975). Theseobservations therefore highlight the posedto the red legs of adults(Hayman et al. 1986). crucialrole of theseestuaries as probably the mostimportant wintering site for the species. RESULTS Although it is clear that our observationscovered a size- ableproportion of the total population,they do not enableus We presenta completelist of all recordsof MagellanicPlov- to make an updatedestimate of what the totalpopulation size ers recordedduring 1998-2002, includingdates, localities may be. The main reasonis evidencethat thereare substan- and the numberand age of birdsobserved (Table 1, seealso tial but uncountedpopulations outside our studyarea. Some Fig. 2). Locations where and visits when we recordedno birds, for example, remain in Tierra del Fuego in winter ploversare not included. (Johnson & Goodall 1965, Jehl 1975, L. Benegaspers. comm.) where the specieshas never been the subjectof a DISCUSSION AND CONCLUSIONS systematicsurvey. Moreover, in winter, our surveywas re- strictedto estuariesbut Magellanic Plovers also occur in Our resultsshow clear patternsof habitatuse and seasonal other coastalhabitats (Narosky et al. 1993, Gonzfilez 1996). movementsin MagellanicPlovers throughout the year. This In addition,our observationsof fairly large flocks are prob- is the casedespite the fact that our surveycoverage was not ably very unusual.Most recordsare of very small numbers comprehensive.The birdsabandon their breedinggrounds in with individualsbeing recorded as far northas Buenos Aires early autumn(March-April) to spendthe winter at the coast. Province(Narosky et al. 1993). Therefore,hundreds of birds They return inland in early spring (August-September) could be scatteredalong the Atlantic coastin winter. Alto- (Fig. 2). Besidesour recordspresented here, this seasonality gether,these factors mean that it is impossibleto arrive at a is also supportedby severalunreported visits that yielded total populationestimate from our observationsalone. We negativeresults. These observationsaimed to confirm the thereforebelieve that a major priority for the conservation absenceof ploversat breedingor winteringareas during the of the speciesshould be a thoroughcensus of the entirepopu- monthsour researchindicated they shouldnot be present. lation throughoutits range. Our observationsof the occurrenceof MagellanicPlovers on On the breedinggrounds, suitable nesting sites appear to estuariesare consistentwith those of Jehl (1975) who re- be scarceand this mustbe exacerbatedby the unstablewater cordedtheir presenceon the Patagoniancoast in winter. levels of lakes and ponds.No doubtthis is why the breed- Our observationsof flocks of 123 and 145 Magellanic ing densityof MagellanicPlovers we foundwas low, though Ploverson the Gallegosand Chico estuaries are probably the it was similar to that reportedby Jehl (1975). We suppose largestaggregations of the speciesever reported.Although thatthe birdsnesting in a hugeinland catchment area become
Bulletin 101/102 August/December 2003 76 Wader Study Group Bulletin concentratedinto the main winteringsites in our studyarea, recordedsuch losses in Magellanic Oystercatchers,which the Gallegosand Chico estuaries. These concentrations may nest in similar habitat (pets. obs.). alsoinclude birds from elsewhere,such as the northernparts Despiteits limitations,our surveyhas shed new light on of Tierra del Fuego. thislittle known species.However, as the MagellanicPlover On the Gallegos and Chico estuaries, we only found hasbeen paid scantattention by researchersand in view the Magellanic Ploversin areasthat were relatively free from importanceof its conservation,many more systematicsur- humandisturbance or human-relatedchange (the west shore veysand searches of potentialhabitat are needed. Currently, of Rfo Chico, Punta Loyola and Isla Deseada).Elsewhere, a year-roundcensus is beingcarried out on the Gallegosand apparentlysuitable places close to highlymodified sites, such Chico estuaries.However, much more effort is requiredin as R•o Gallegoscity, are avoided.We infer that Magellanic otherareas of high concentrationsas well asless visited sites, Ploversare particularlyvulnerable to humandisturbance and, suchas the river and estuaryof Rio SantaCruz, as well as given the large numbersof birdsrecorded for the area, we the breedinggrounds. recommendincreasing the protectionof key sitesfor thisand the otherspecies with which it often associates(Magellanic ACKNOWLEDGEMENTS OystercatcherHaematopus leucopodus, Two-banded Plover Charadrius falklandicus, Rufous-chested Plover Ch. mo- We thankPatricia Gonzalez for encouragementand informa- desms,Baird' s SandpiperCalidris bairdii andWhite-rumped tion, JorgePerancho and Pablo and Silvina Sturzenbaumfor SandpiperC. fuscicollis). field assistanceand personalrecords, Martina McNamara, Although there is no mentionin the literatureof rivers as PatriciaRacamato, Ricardo Nfifiez and Percy Beecher for the breedinghabitat for MagellanicPlovers (Jehl 1975,Hayman companyin the field. PrefecturaNaval Argentinaprovided et al. 1986, Fjelds•t& Krabbe 1990), we found the species theaccess to Isla Deseada.The editor,Humphrey Sitters, and by rivers on six occasions(Fig. 2). Most significantly,one reviewer JosephJehl Jr. provided helpful commentsand of theserecords related to a pair with a small chick (Site 3, ideasthat greatlyimproved the manuscript. Fig. 1, Table 1, Plate2). This suggeststhat they nested by the river, asthe closestsuitable lake was about10 km away and REFERENCES the chick was too young(probably <10 days)to havewalked so far (Imberti 2003). It is also interestingthat they were BirdLife International 2001. BirdLife'sonline World Bird Database.the nestingso late in the season(February). This suggestseither site.tbr bird conservation. Version 1.0. Cambridge, UK: BirdLife International. a long breeding seasonwith the raising of two or more Blanco,D.E. & Canevari, P. 1995. Situaci6nactual de chorlosplayeros broodsor one or more attemptsafter failure. migratoriosde la zona costerapatag6nica (Provincia de Rio Negro, Another interestingobservation was that of a pair feed- Chubuty Santa Cruz). Informes Tdcnicosdel Plan de Manejo Inte- ing two well-developedjuveniles on 6 December2000 (Site grado de la Zona Costera Patagdnica 3: 1-26. 12, Fig. 1, Table 1). Although Magellanic Plovers lay two Fjelds•, J. & Krabbe, N. 1990.Birds of theHigh Andes.Zoological Mu- eggs,the weaker chick, usually the secondto hatch,normally seum,University of Copenhagen,Denmark. dies of starvation(Jehl 1975). Gonz•ilez,P. 1996. Habitatpartitioning and the distributionand seasonal A particularlypuzzling observationis that of a juvenile abundancesof migratoryplovers and sandpipersin Los Alamos,Rfo Negro, Argentina. Pages93-102 in P. Hicklin editor. Shorebird ecol- on the extremely early date of 3 October (Site 8, Table 1, ogy and conservationin the WesternHemisphere. International Wader Figs. 1 & 2). For a juvenile to havefledged by then,the egg Studies, Quito, Ecuador. musthave been laid in earlyAugust, yet it is notthought that Grigera,D. & 0beda,C. 1997.Recategorizaci6n delestado de conser- MagellanicPlovers start breeding until early September (Jehl vaci6n de la fauna de la Patagonia Argentina, Antfirtida e Islas del 1975).It wasin the companyof a pair of adultsand this sug- Atlfintico Sur: un analisisde susresultados. Gayana Zoologica 61: 113-124. geststhat they raised it. Thereforeperhaps at leastsome birds Harris, G. 1998.A Guideto thebirds and mammalsof coastalPatagoma. nestearlier than has been recorded. An alternativeexplana- PrincetonUniversity Press,New Jersey. tion is that the juvenile was a bird hatchedvery late in the Hayman, P., Marchant, J. & Prater, T. 1986.Shorebirds: An identtfi- previousbreeding season (such as the chick found at Site 3 cation guide to the waders of the world. ChristopherHelm, London. on 12-13 February2002) and still showedcharacteristic ju- Humphrey, P.S., Bridge, D., Reynolds, P.W. & Peterson,R.T. 1970. venile plumageand leg colour. Birds qf Isla Grande (Tierra del Fuego). SmithsonianInstitution, During winter, the birds fed on the estuariesin areasof Washington D.C., 411 pp. Imberti, S. 2003. Notes on the distributionand naturalhistory of some softmud and scattered pebbles, usually high in theintertidal birdsin SantaCruz andTierra del Fuegoprovinces, Patagonia, Argen- zone, far from the waterline (Plate 3). They roosted on tina. Cotinga 19: 15-24. shinglebanks or salt marshes.These observationsare simi- Jehl, J.R. 1975.Pluvianellus socialis: biology, ecology and relationships lar to thosereported by Jehl (1975). of an enigmatic Patagonian shorebird. San Diego. Soc. Nat. Htst On their wintering grounds,probable threats to Magel- Trans. 18: 31-72. lanic Ploversinclude predation by feral animals(mostly cats Johnson,A.W. & Goodall, J.D. 1965. The Birds qt' Chile and adjacent regions of Argentina, Bolivia and Petri. Vol. 1. BuenosAires, Platt and dogs)and habitatdestruction due to pollutionfrom the Establecimientos Gr•ficos, S.A. constantdumping of garbageand sewage as well asoil spills Narosky, T., Di Giacomo, A.G. & Babarskas, M. 1993. Presencla aroundRio Gallegoscity andPunta Loyola harbour.On the invernal de Pluvianellus socialis en la provincia de BuenosAires, breedinggrounds, probably the greatestdanger is trampling Argentina. Hornero 13:309-310. of nestsand chicksby grazinganimals. Certainly we have
Buffetin 101/102 August/December 2003