Noteson tropical terns Mexico

Steve N. G. Howell, Sophie Webb and Barbara M. de Montes

OOTYTERNS (STERNA FUSCATA) breedvery locally along the east coastof Mexico. Pa7nter (1955) consideredthe only cdlonyin the Yucatfin Peninsula to be on Arrecife Alacrfin,having found no evidenceto supportthe reportsof Friedmannet al. (1950) that the species breeds on Cayos Arcas and Isla Mujeres. How- ever, the American Ornithologists' Union (1983) maintainsthat Sooty Terns formerly bred on Isla Mujeres and also on Isla Cancfin.The species also may breed on Isla Contoy (de Montes, pers. obs.) though confirma- tion has not yet been obtained.There are no confirmedbreeding records for the Gulf •oast of Mexico. We report on the continued exist- ence of the Isla Cancfincolony which, with the colony on Arrecife Alacr•n, makesup the known breedingpopula- tion of SootyTerns in easternMexico. Unfortunately,as with s6 many tern colonies, the Cancfn birds are threat- ImmatureBlack (lower) and Brown noddies,CancrOn, July 9, 1988. ened by increasing human pressure. Following our observations at Isla Cancfin we researched the status of the Photographsby SteveN. G. Howell and SophieWebb Bridled Tern (Sterna anaethetus),and here clarify its occurrencein Mexico. We also document the first Mexican recordof the Black Noddy.

Volume 44, Number 3 381 The Cancun colony. the breeding terns and, hopefully, to About 200 meters off the beach at photographthe Black Noddies. the Hotel Camino Real on Isla Cancfin, We all headed out to the beach on QuintanaRoo, is a smallrock, barely the afternoon of July 9, 1988, and an islet. Since1974, up to 600 Sooty Howell and Webb swam out to the Terns and 190 Brown Noddies (Anous colony. Their census of the Sooty stolidus)have been seenat the islet be- Terns revealed 35 nests with single tween April and September (de eggs, 14 newly hatched chicks, and Montes, pets. obs.) thoughthey have four medium-sizedchicks, represent- likely beenthere for manyyears. ing a total of 53 pairs. Undoubtedly some chicks were missed due to their On the afternoonof July 8, 1988, • ...... •..,-• . . ..',.• Howell and Webb stoppedby to check crypticcoloration and tendency to hide Comparisonof eggsof Bridled (left) and on the colony,which is threatenedby amongthe rocks,but we doubtthat the Sootyterns at theCanc•n colony. increasing,but oftenunwitting, distur- actively breeding population com- bancelinked to the rapid touristdevel- prised more than 100 pairs. At most amongthe people,including tourists, this would account for 200 of the 550 of Cancfin.It is hopedthat disturbance to 600 adult birds present.Harrington can be minimized and that the terns (1974) showedthat Sooty Terns may will continue to breed there. return to a colony in their third and fourthyears, but that most do not breed Black Noddies beforetheir sixthyear; this wouldhelp As on the previous afternoon, on accountfor the surplusbirds. No band- July 9, 1988, noddiescame to roost on ing has been done at the Cancfin the islet and by 1745 hrs both Black colony but at least three Sootiesthere Noddies were back at their same worebands (all on rightleg, apparently perches.Close-range views enabledus silver USFW bands)indicating a de- to seeall features,and numerouspho- gree of immigration,or at least visita- tos were taken. From shore, with a tele- tion, from other colonies. scope,the most obvious featureswere Howell and Webb found three Bri- the relatively uniform blackish dledTern nests, each with a singleegg, plumage (primaries not signficantly The Canctincolony, resort development in and also found a newly hatchedBri- darker than the back as on Brown Nod- the background. dled chick. As indicatedin Bent (1921) dies), and sharply contrastingwhite the nests were relatively well hidden cap, reminiscent of a White-crowned opmentof Cancfin.On their arrival at among the rocks and vegetation com- Pigeon (Columba leucocephala).The 1700 hours no Brown Noddies were paredto the exposedSooty Tern sites. Black Noddies' smaller size was obvi- present, but 10 to 11 adult Bridled The Bridleds' eggs were slightly ousin direct comparisonwith Browns. Terns were seen around screaming smaller than those of the Sooties and At sea the Blacks' relatively fluttery Sooties. No time was available to visit differed in their pale brownish-buff flight enabledus to pick themout quite the rock that day, but observations (rather than whitish) coloration and easily.The slenderbill was only appar- were continued from shore. At 1710 their finer dark spotting.Bridled Terns ent at closerange. Strongly contrasting hrs Brown Noddiesbegan arriving in breedon severalcays off Belize (Rus- white caps, relatively abradedflight ones and twos and at 1740 hrs, Howell sell 1964;Pelzl 1969) sotheir presence feathers, and lack of contrast between spotted a Black Noddy (Anous in QuintanaRoo is not surprising. back and tail indicate that both were tenuirostris)among them. A few min- Therewas no evidenceof nestingby immatures (Harrison 1983, 1987; Pratt utes later a second Black Noddy Brown Noddies and, of the 20 birds et al. 1987). appearedand both were watched for that arrived to roost before dark, the The discoveryof Black Noddies at about 30 minutesas they preenedand majority were immature.The observa- Cancfinis not too surprisingsince the flew aroundbefore settling down to tions of de Montes in the 1970s and speciesis a rare but fairly regularvisi- roost. Plans were made to visit the rock early 1980s indicatedthat Brown Nod- tor to the Dry Tortugas, Florida the followingday to make a censusof diesprobably did breedon the islet, but (A.O.U. 1983). However, it is interest- increaseddisturbance may have caused ing to note that the nearest known them to abandon the site. breedingcolony of the Black Noddyis On both days we observed the off Venezuela (A.O.U. 1983); Black colony,numerous people, both tourists Noddies bred on Southwest Cay, and local residents,caused much alarm Belize, from at least 1862 to 1907, to the terns by swimming out and but there are no recent records walking aroundon the islet. Most of (Russell1964, Pelzl 1969). Meyer de the disturbancewas unintentional, and Schauenseeand Phelps (1978) re- the peoplewe spoketo oftendid not re- portedthat the Black (Lesser)Noddy alizethe pressurethey were putting on "Breedsin many small islandsin the Bridled Ternat Canctin,July 9, 1988. the colony.De Montes is trying to in- Caribbean," but apparently no data creasepublic awarenessof the colony supportthat statement(cf. Bond 1971).

382 AmericanBirds, Fall 1990 Tern was observed at 18ø50'N,104 ø LITERATURE CITED 11'W, close to Manzanillo, on June 4, AMERICAN ORNITHOLOGISTS' UNION. 1982 (Pitman 1986). In Guerrero, 1983. Check-list of North American Birds, Richard Ryan (pers. comm.) saw a 6th Edition: 56-57. A.O.U. Washington, few Bridled Terns off Zihuatanejo in D.C. October 1988, and again in November BENT, A. C. 1921. Life histories of North 1989. Americangulls and terns.U.S. Nat. Mus. Bull. 113. Govt. PrintingOffice. Washing- Bridled Terns breed widely in the ton, D.C. Caribbean (A.O.U. 1983, Bond 1971) BOND, J. 1971. Birds of the West Indies, 2nd but have not previously been docu- Edition. HoughtonMifflin Co. Boston. mented from the east coast of Mexico. FOSBERG, F. R. 1962. A brief surveyof the caysof ArrecifeAlacrgn, a MexicanAtoll. In additionto the breedingat Cancfin Atoll Research Bulletin No. 93. Pacific detailed above we are aware of the fol- ScienceBoard, Washington, D.C. lowingrecords in easternMexico. FRIEDMANN, H., L. GRISCOM, and R. T. In Quintana Roo, since the mid MOORE. 1950. Distributional Check-list of the Birds of Mexico. Pacific Coast Avi- 1970s, up to six Bridled Terns have faunaNo. 29. CooperOrnith. Club, Berke- been seen on Isla Cozumel between ley. late April and August (John Guamac- Two immature Black Noddies (lower) and HARRINGTON, B. A. 1974. Colony visita- tion behaviourand breeding ages of Sooty immature Brown Noddy for comparison, cia, Howell, Kenn Kaufman, Andres M. Sada);on July 12, 1988 Howell and Terns (Sterna fuscata). Bird-Banding CancrOn,July 9, 1988. 45:115-144. Webb confirmedbreeding when they HARRISON, P. 1983. Seabirds: An Identifi- It seemslikely, however, that Black found two nests, each with a single cationGuide. Houghton Mifflin, Boston.-- Noddies will be found in 'the West egg, on a small rocky islet near Punta 1987. Seabirds of the World: A Photo- Indies, perhaps even breeding, if Celarain at the south end of Cozumel. graphicGuide. ChristopherHelm, London. observers check suitable areas. Other coloniesprobably remain to be MEYER DE SCHAUENSEE, R. M. and W. H. PHELPS, Jr. 1978. A Guide to the Birds discovered.Banco Chinchorro,a large of Venezuela. Princeton Univ. Press, reef 30 kilometers offshore and 165 Statusof Bridled Terns in Mexico Princeton. kilometers south of Cozumel, has PAYNTER, R. A., Jr. 1955. The ornithogeog- Most literature cites only one old never been visited by an ornithologist raphy of the YucatfinPeninsula. Peabody record of the Bridled Tern from Mex- Mus. Nat. Hist. Bull. 9. New Haven. in summer. In Yucatfin, at Arrecife ico, a seriesof eight birdscollected by PELZL, H. W. 1969. Preliminary Report. Alacran, Fosberg (1962) reported Nelson and Goldman on the rocky Birdsof the BritishHonduras Keys. (Un- "Many [Bridled Terns] seenon July 5 published). islets at Zihuatanejo, Guerrero, on in a mixed flock with black terns [= PITMAN, R. L. 1986. Atlas of Seabird Distri- April 9, 1903 (Ridgway 1919, Fried- bution and Relative Abundance in the East- Chlidonias niger]." However, given mann et al. 1950); these include the ern Tropical Pacific. National Marine that he apparentlymisidentified Sand- type specimenof S. a. nelsoni,the sub- FisheriesService, La Jolla, California. wich Terns (S. sandvicensis)as Com- speciesbreeding along the Pacific coast PRATT, H. D., P. L. BRUNER, and D. G. mon Terns (S. hirundo), and that no BERRETT. 1987. A Field Guide to the of Middle America. It is likely that ornithologistshave reported Bridled Birds of Hawaii and the TropicalPacific. Zihuatanejowas, and may still be, the Princeton Univ. Press, Princeton. Terns from Arrecife Alacrfin, the siteof a breedingcolony. However, the RIDGWAY, R. 1919. The Birds of North and A.O.U. (1983) described the statusin recordshould, for the present,be con- Middle America, Part 8. Bull. U.S. Nat. sideredhypothetical. Mus. No. 50. Washington,D.C. Mexico as "Rangesat sea...offGuer- The foregoingrecords indicate that RUSSELL, S. M. 1964.A distributionalstudy rero." Tuck and Heinzel (1978) and of the birds of British Honduras. Ornith. Bridled Ternsbreed locally alongboth Harrison(1983, 1987) map a continu- Monog. No. 1. ousbreeding range for the BridledTern coastsof Mexico. The speciesdoes not TUCK, G. S., and H. HEINZEL. 1978. A from westernMexico to Colombia, but seem to nest in large, conspicuous Field Guide to the Seabirds of Britain and the World. Collins, London. this is largely based on assumption. coloniesas does the SootyTern andthe sites mentioned above are all small Bridled Terns almost certainly breed rocks or islets close to shore. Ob- locally alongthe Mexican Pacific coast from at least Nayarit to Guerrero,but serversvisiting Mexico in the summer should be on the lookout for other other than the specimensmentioned above,we are aware of only the fol- coloniesas they are almost certainly there to be found. ß lowingrecords. In Nayarit, the specieswas seenat San Blas, from 1970 to 1980 (Peter Alden pers. comm., Kenn Kaufman ACKNOWLEDGMENTS pers.comm.) from late March to May, We wish to thank Peter Alden, John Guar- --Point ReyesBird Observatory, but no visits were made during the naccia, Kenn Kaufman, Richard Ryan, and 4990 ShorelineHighway, summer.On August 5, 1988, Howell Andres M. Sada for helpful commentsand StinsonBeach, CA 94970 (Howell); and Webb estimated17 to 20 pairs of unpublishedobservations of Bridled Tern in Box 664, Wellfleet,MA 02667 Bridled Terns at San Blas, and ob- Mexico, and Kenn Kaufman and Mary (Webb) ; LeCroy for their helpful reading of the servedadults feeding chicks (photos manuscript.This is publicationNumber 407 Apdo.Postal #8, Cancurt, taken). In Colima, a single Bridled of the PointReyes Bird Observatory. Ouintana Roo, Mexico (de Montes).

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