The Condor 89:2X-281 0 The Cooper Ornithological Society 1987
PRESENT STATUS OF THE FLIGHTLESS CORMORANT, GALAPAGOS PENGUIN AND GREATER FLAMINGO POPULATIONS IN THE GALAPAGOS ISLANDS, ECUADOR, AFTER THE 1982433 EL NINO
CARLOS A. VALLE Charles Darwin ResearchStation, Casilla H-39, Guayaquil, Ecuador
MALCOLM C. COULTER Savannah River EcologyLaboratory, P.O. Drawer E, Aiken, SC 29802
Abstract. The 1982-83 El Niiio/Southem Oscillation was the most severe recorded in the tropical Pacific Ocean. It was a period of low ocean productivity. Many seabirdsin the GalapagosIslands, including the GalapagosPenguin (Spheniscus mendiculus) and the Flight- less Cormorant (Nannopterum harrisi), did not breed. The cormorant and penguin popu- lations were reduced by 49 and 77%, respectively. The Greater Flamingo (Phoenicopterus ruber) population size remained unchanged,Between July 1983 and September 1984, the cormorant population recovered whereas the penguin population had not recovered. Key words: Galapagos;El Nirio; Southern Oscillation; ENSO; Flightless Cormorant; GalapagosPenguin; Greater Flamingo.
and present the results of our own censuses INTRODUCTION through 1984. The El Nifio/Southem Oscillation (ENSO) phe- nomenon that occurred in 1982-1983 was the METHODS most severe ever recorded in the eastern equa- Cormorants and penguins were censusedalong torial Pacific Ocean with large changes in fish, the shoresof Femandina and Isabela Islands 29 marine mammal, and bird populations (Barber August to 8 September 1983, 7 to 15 January and Chavez 1983, Cane 1983, Limberger et al. 1984, and 4 to 14 September 1984. Individual 1983, Schreiber and Schreiber 1984). The Ga- birds were counted along the coast and in the lapagosIslands, about 950 km west of mainland adjacent waters from an inflatable boat 15 to 50 Ecuador, were surrounded by particularly warm m from shore. Along 10% of the coastline, we ocean water, there was heavy rainfall (Cruz and counted birds from a larger boat 50 to 150 m Beach 1983, Grant 1984) fish populations de- offshore. clined (Grove 1984), and there were breeding Landings were made at 95% of all sites where failures of marine iguanas (Amblyrhynchus cris- nesting cormorants or nest traces were seen. We tatus) (Laurie 1983) and fur seals(Arctocephalus recordedthe numbers of adults (blue eyes [Snow gufupagoensis)(Limberger et al. 1983). The pop- 19661) subadults (brown eyes), juveniles and ulations of Flightless Cormorants (Nannopterum chicks that were still at the nest, as well as the harrisi) and Galapagos Penguin (Spheniscus number of active nests, nest contents, type of mendiculus)decreased (Valle 1984). The unusual nest material, and number ofnesting individuals. ENS0 conditions lasted from October 1982 to We were unable to distinguish subadults from July 1983 when conditions began to return to adults when they were in the water away from normal. We censusedthe populations of Flight- the colony. less Cormorants, Galapagos Penguins, and Simultaneous counts of flamingos were made Greater Flamingos (Phoenicopterusruber) to re- at 1O:OOon 22 March 1984 at all the 32 locations cord the effects of the 1982-83 ENS0 on pop- where flamingos are known to occur. ulation sizes and to record any recovery in the populations since the phenomenon. In this paper RESULTS AND DISCUSSION we summarize the results of previous censuses END OF THE ENS0
I Received3 January1986. Final acceptance27 Oc- The 1982-83 ENS0 was a period of warm ocean tober 1986. temperature and heavy rains, during which there
[2761 GALAPAGOS BIRDS 277
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‘A’M’J’J’A’S’O’N’D J’F’M’A’M’J’J’A’S’ 1983 1984 ISABELA FIGURE 1. Seatemperatures among the Galapagos IALBEMARLE) Islandsin 1983 and 1984. /
was little breeding activity among seabirds(Mer- FIGURE 2. Areas censusedfor Flightless Cormo- len 1984; Valle 1985; Coulter, unpubl. data) and rants and Galapagos Penguins. The small circles in- heavy mortality among some seabirds.Along the dicate cormorant nesting areas. coastsof Isabela and Fernandina, Valle (unpubl. data) counted hundreds of dead Blue-footed cormorantswere countedand by September 1984, Boobies(&da nebouxii)and Brown Pelicans (Pe- 869 cormorants were counted. lecanusoccidentalis). The end of the ENS0 in Distribution.The entire range of the Flightless July 1983 was indicated by the lowering of sea Cormorant is limited to the north and west coasts temperatures to more normal levels (Fig. 1) and of Isabela Island and the entire coast of Fernan- a reduction in rainfall. dina Island (Fig. 2). During our visits we cen- CORMORANTS sused the entire area. The birds and breeding areas were concentrated along the north coast of Populationsize. In 196 1 Leveque (1963) counted Isabela Island (from Punta Vicente to Cabo 501 cormorantsin approximately 75% of the area Berkeley), along the coast of Isabela Island at where cormorants are found. He estimated a to- Bahia Elizabeth, and along the eastern coast of tal population of 1,000 individuals. In 1962 Femandina Island (Fig. 2). Brosset (1963) estimated a population of be- Reproduction.During the census taken im- tween 3,000 and 5,000 birds. In 1971, Harris mediately after the ENS0 (August/September (1974) estimated from numbers of active or re- cently used neststhat there were 406 pairs in the area censused by Leveque, from which he ex- TABLE 1. Numbers of cormorantscounted along the trapolated a total population of between 700 and coasts of Fernandina and Isabela Islands during cen- susesfrom 1977through 1984.Data from Tindle (1977) 800 pairs. Although there is no available infor- Harcourt (1980) and this report. mation on the population between 197 1 and
1977, there has been no suggestionof any large Year population decline during this period. Since 1977, Island 1977 1980 1983 1984* 19x4** the population estimates have remained fairly Femandina 326 293 169 278 321 stable at about 650 to 800 adults, with a sharp Isabela 357 509 240 359 548 decline of about 50% in 1983, which coincided Total 683 802 409 637 869 with the ENS0 (Table 1). In August and Sep- *January. tember 1983, after the ENS0 had ended, 409 ** August/September. 218 CARLOS A. VALLE AND MALCOLM C. COULTER
TABLE 2. Number of nesting pairs of cormorants and proportion of the populationduring the post-ENS0 censuses.
Number of nesting pain (percent) of the population in
Femandina 62 (73%) 39 (28%) 63 (39%) Isabela 81 (68%) 65 (36%) 103 (38%) Total 143 (70%) 104 (33%) 166 (38%)
251 portunistic breeders, and females which leave their mates to finish raising the young may breed 0 1 successfullytwice during a year (Tindle 1984). 1983 BetweenSeptember 1983 and September 1984, FIGURE 3. Numbers of nests of Flightless Cormo- the population increased by 112%, or 2.3 young rants in different stagesof breeding at the times of the introduced into the population per pair in a 12- 1983 and 1984 censuseson Isabela Island (I) and Fer- month period. The production estimated for this nandina Island (F). study period is higher than that suggestedby Har- ris (1977) for a previous non-ENS0 year. He 1983) adults, chicks, most of which were less calculated a reproductive rate of 0.76 young per than a month old, and a few juveniles still de- nesting attempt in 1970 and 197 1, and juvenile pendent on their parents were observed; there survival rate of 92% in 1970. Assuming two were no subadults (Fig. 3). We counted 143 breeding attempts per year, the production would breeding pairs, representing 70% of the total be 1.5 fledglingsof which 1.4 would be recruited number of birds counted (Table 2). The nests into the population, less than the 2.3 calculated observed during this censuswere constructed of for 1983/1984. dead Blue-footed Boobies, Brown Pelicans, and marine iguanas as well as mangrove twigs and PENGUINS leaves, and black coral (Anthipathes sp.). Nests Population. Early estimates of the Galapagos are usually made of marine algae (Surgussumsp., Penguin population were vague. In 1962 Brosset Laminaria sp., and Ulva sp.), which had all but (1963) estimated the population to be between disappeared during the ENSO. 3,000 and 5,000 individuals. Leveque (1963) es- In January and Septemberof 1984, we counted timated 500 breeding pairs, but later revised the 104 and 166 nesting pairs, respectively. This was total estimate to 1,500 individuals (Leveque a lower proportion of the population than ob- 1964). Harris (1977) later suggesteda population served in 1983 and probably reflected the ad- size similar to that put forward by Brosset,3,000 dition to the population of juveniles and sub- to 5,000. Boersma (1977) censused the entire adults which did not breed. In all three censuses breeding range in 1970 and again in 197 1 (Table we counted a total of 4 13 breedingattempts which 3). She estimated a total population of between indicates that the majority of the adults bred 6,000 and 15,000 birds. during the post-ENS0 period and that many bred Subsequent censuses have indicated a rela- more than once. Flightless Cormorants are op- tively stable population. In 1980 there was a de-
TABLE 3. Counts of Galapagos Penguins around the coasts of Femandina and Isabela Islands in censuses made since 1970. Data from Boersma (1977) Harcourt (1980), and this report. See Figure 2 for areas.
Yeal- 1970 1971 1980 1983 1984* 1984**
Number of penguins 1,584 1,931 1,716 398 463 435
*January. ** August/September. GALAPAGOS BIRDS 219
TABLE 4. Numbersof Greater Flamingoscounted r in censusessince 1967. Data. from de Vries (unpubl. observ.), Harcourt (198 1, 1982), and this report.
Year 1967 1968 1976 1981 1982 1984
Numbers of individuals 317 512 442 371 418 394
nesting at only six small brackish lagoons: El Sarten and the Salt Mine on Santiago Island, Bainbridge Rocks, Poza de1 Cementerio and Quinta Playa on Isabela Island, and at Punta Cormorant on Floreana Island. The Greater Fla- FIGURE 4. Locationsof areaswhere Greater Fla- mingo is the only flamingo speciesthat breeds mingoshave beenobserved among the GalapagosIs- in groups as small as 50 or fewer pairs (Tindle lands. 1978). These flamingos can reside in the Gala- pagosIslands, perhaps, becausethey are able to breed successfullyin small colonies. During the cline in numbers in areas seven and eight (Fig. 1984 censusno nesting was observed, although 2). Harcourt (1980) has suggestedthat this may six pairs were observed nesting at Quinta Playa have been related to predation by feral dogsand in April 1984 (Tupiza, pers. comm.). During the the eruption of Volcan Chico (Cerro Azul) on census15% of the flamingos were juveniles com- Isabela Island in November 1979. During this pared with 9% recorded in 1982. This indicates eruption the lava reached the sea, raising the that there was a significant amount of breeding water temperature and modifying the coastline after the ENSO. around Bahia Elizabeth. Nevertheless, in 1982- CONCLUSION 1983 there was a 77% reduction associatedwith the ENSO. The population has not recovered. The 1982-83 ENS0 phenomenon was a period Few juveniles have been observedduring the last of low ocean productivity and heavy rains. Many three censuses,suggesting poor reproduction and animals that depended on marine resourcessuf- recruitment. fered heavy mortality. Among seabirdsthere was Reproduction.During the three censusessince little reproductive activity and many birds may the ENSO, many pairs have been observedcourt- have left the Galapagos.Both the GalapagosPen- ing. Yet only 29 juveniles were counted during guin and the Flightless Cormorant are endemic the two 1984 censuses.This indicates a lack of to the archipelago and severe declines in their actual reproduction or low reproductive success. numbers or inability to recover from a decline may have important consequencesfor the species. GREATER FLAMINGOS The Greater Flamingo that breeds in the Gala- Populationand distribution.Leveque (1963) es- pagos also breeds in the Caribbean but it is timated a population size of less than 150 fla- doubtful that the Galapagospopulation has con- mingos. However, based on complete censuses tact with other populations. After the ENS0 the since 1967, it is estimated that the population is FlightlessCormorant population was 5 1% as large closer to 400 individuals (due to the discovery as it had been during censusesbefore the ENSO. of additional feeding sites between censuses).At There is no evidence that cormorants bred dur- present there are 32 areas where flamingos have ing the 1982-l 983 event and there was probably been observed (Fig. 4). Furthermore, the popu- heavy mortality. This contrasts with the 1972 lation seems to have remained relatively stable. ENS0 when Harris (1979) recorded some, albeit In January 1984, 394 birds were observed, only low, reproductive effort and high juvenile mor- 12% less than the 4 18 counted in January 1982 tality. The Galapagos Penguin population was (Table 4). Apparently the population was not reducedto 23% of its previous levels. In contrast greatly affected by the ENSO. to these species,the flamingo population did not Reproduction.Flamingos have been observed decreasesignificantly during the ENSO. 280 CARLOS A. VALLE AND MALCOLM C. COULTER
During the year after the ENS0 event, the cor- to thank the many peoplewho collaboratedin the field- morant population increased to above its pre- work, particularly-S. Ayala, H. Beck, C. Rector, L. vious levels. This was due to nearly all of the Riedel, J. Rodriguez, I. Stupakoff, C. Ulloa, J. Villa, W. Weber, and studentsand employees of the CDRS adults in the population breeding (and many and the GNPS. S. Harcourt, M. Hurtado, M. Mac- breeding more than once), and to low mortality Donald. G. Reck. and T. de Vries imoroved the manu- rates and high recruitment of juveniles into the script with thei; comments. A. Fgjardo typed the population. Such high reproductive effort is pos- manuscriptand C. McFarling translatedit. J. Coleman prepared the figures. Preparation of this manuscript sible because successfullybreeding females can was supported in part by the CDRS and by contract reproduce twice a year; and males that breed DE-AC09-76SROO-8 19 between the University of successfully, while reproducing at somewhat Georgia’s SavannahRiver EcologyLaboratory and the longer intervals than females, probably breed at U.S. Department of Energy.This is contribution num- intervals of less than a year. ber 389 of the Charles Darwin Foundation. The GalapagosPenguins, in contrast, have not LITERATURE CITED recovered. The 1984 census indicated that the population had only increased 9% since the end- BARBER,R. T., AND F. P. CHAVEZ. 1983. Biological conseauencesof El Niiio. Science222: 1203-l 2 10. ing of the ENSO. The low number of juveniles BOERSMA,P. D. 1977. An ecologicaland behavioral observed suggeststhat penguins have reproduced study on the GalapagosPenguin. The Living Bird very little in 1983 and 1984. Penguins probably 15:43-93. have much stronger pair bonds than the cor- BROSSET,A. 1963. La reproduction des oiseaux de mer des iles Galapagosen 1962. Alauda 31:81- morants and usually breed with the same mate 109. from year to year. Pair bonds may have been CANE, M. A. 1983. Oceanographicevents during El disrupted during the ENSO, through mortality Nifio. Science 222:1189-i 195. or through separation of members of pairs when CRUZ. F.. AND T. BEACH. 1983. Weather data on food was scarce. The many courting pairs that goreana, 1982-1983. Noticias Galapagos38:28. GRANT,P. R. 1984. Extended rainfall d&ng the El we observed during all the censuses after the Niiio event of 1982-83. Noticias Galaoaaos- _ 39: ENS0 suggests that it may take a long time for 10-11. pair bonds to become established and for the GROVE,J. S. 1984. Influence of the 1982-83 El Nifio birds to begin laying eggs. It may, then, take on the icthyofauna of the Galapagosarchipelago. Tropical Ocean-AtmosphereNewsletter 28: 18-l 9. many years for the penguin population to re- HARCOURT,S. 1980. Report on censusof the Flight- cover. less Cormorant (Nunnopterum harrisi) and Ga- The numbers of Greater Flamingos were ap- lapagosPenguin (Spheniscusmendiculus) around parently little affected by the climatic changes Femandina and Isabela. Unpubl. report, Charles during the ENSO. They do not feed on marine Darwin ResearchStation files. HARCOURT, S. 198 1. The Galapagos Flamingo animals and were not affected by changes in the Phoenicopterusruber ruber. Unpubl. report, Charles oceans. One might have expected that the in- Darwin ResearchStation files. crease in rain may have decreased the salinity in HARCOURT,S. 1982. GalapagosFlamingo census- the brackish lagoons, and so affected the repro- 1982. Noticias Galapagos36: 15-16. HARRIS,M. P. 1973. The Galapagosavifauna. Con- duction and density of their prey. If this did oc- dor 751265-278. cur, the changes were not sufficient to affect the HARRIS,M. P. 1974. A complete censusof the Flight- flamingo population size. lessCormorant (Nunnopterumharrisi). Biol. Con- serv. 6:188-191. ACKNOWLEDGMENTS HARRIS,M. P. 1977. Comparative ecologyof seabirds in the Galapagos Archipelago, p. 65-76. In B. This is part of a long-term project to monitor seabirds Stonehouseand C. M. Perrins [eds.],Evolutionary and lagoon birds in the Galapagos,carried out by the ecology. Charles Darwin ResearchStation (CDRS) and the Ga- HARRIS, M. P. 1979. Population dynamics of the lapagos National Park Service (GNPS). Funding for FlightlessCormorant (Nunnopterumharrisi). Ibis the censuswork was provided by grantsfrom the World 121/2:135-146. Wildlife Fund to the CDRS. We are grateful to the LAURIE,A. 1983. Marine iguanas suffer as El Nifio EcuadorianGovernment and the GNPS for permission breaks all records. Noticias Galapagos38: 11. to work in the GalapagosNational Park. We thank the LEVEQUE,R. 1963. The status of some rarer Gala- CDRS for supporting this research.Our appreciation pagosbirds. Int. Count. for Bird Preservation9:96- goesto the director, Gunther Reck, and to Mario Hur- 98. tado and Tjitte de Vries who made this work possible. LEVEQUE,R. 1964. Notes sur la reproduction des The crew of the BeagleIV were a great help during the oiseauxaux iles Galapagos.Alauda 32:5-44, 8 l- voyages and made the trips more pleasant. We wish 96. GALAPAGOS BIRDS 281
LIMBERGER,D., F. TRILLMICH,G. L. KOOYMAN,AND Phoenicopterusruber in the Galapagos Islands. P. MAJLUF. 1983. Reproductive failure of fur- CDRS Annual Report, 1978. sealsin Galapagosand Peru in 1982-1983. Trop- TINDLE,R. 1984. The evolution ofbreeding strategies ical Ocean-Atmosphere Newsletter 2 1:16-l 7. in the FlightlessCormorant (Nunnopterumharrisi) MERLEN,G. 1984. The 1982-83 El Niiio: some of its of the GalapagosIslands. Proc. Linn. Sot. Lond. consequencesfor Galapagoswildlife. Oryx 18:2lO- 21:157-164. 214. VALLEC., C. A. 1984. Breve nota sobre el impact0 SCHREIBER,R. W., AND E. A. SCHREIBER.1984. Cen- de El Niiio 1982-l 983 en las poblacionesde aves tral Pacific seabirdsand the El Nifio southern os- marinas en Las Galapagos.Revista Comisibn Per- cillation: 1982 to 1983 perspectives.Science 225: manente de1Pacific0 Sur 15:259-26 1. 713-716. VALLEC., C. E. 1985. Alteracibn de las poblaciones SNOW,B. K. 1966. Observations on the behaviour de1cormoran no volador, el pinguino y otras aves and ecologyof the FlightlessCormorant Nunnop- marinasen Galapagospor efecto de El Niiio 1982- terum harrisi. Ibis 108:265-280. 83 y su subsequenterecuperation, p. 245-258. In TINDLE,R. 1977. Censo de cormoranes (Nunnopte- G. R. Robinson and E. Del Pino [eds.],Galapagos rum harrisi). Unpubl. report, Charles Darwin Re- 1982-1983: a chronicle of the El Niiio. Springer searchStation files. Verlag, New York. TINDLE,R. 1978. Studies on the Greater Flamingo