Records of Tropicbirds in the North Atlantic and Upper Gulf of Mexico, with Comments on Field Identification

DISTRIBUTION, IDENTIFICATION

Records of tropicbirds in North Atlantic and upper Gulf of Mexico, with comments on field identification

A review of the occurrenceof Red-billed Tropicbirds suggeststhat "some sight records of White-tailed Tropicbirdsmay be suspect"

David S. Lee, David B. Wingate, and Herbert W. Kale H

ESPITEITS SEEMINGLY accidental that there was no reason to question June 10, 1963 on the shore of Bergen occurrence, recent records of the tropicbird sight identifications and of Beach, Jamaica Bay, Kings County, Red-billed Tropicbird, Phaethon aethe- limiting the information necessary for New York (Bull 1964). Bull noted that reus, in the North Atlantic suggestthat them to quickly make species specific this bird was probably driven to Long It may occur more frequently than is identifications in the field. Considering Island by a tropical disturbanceof June generally believed. also that most of the distinguishingfield 4 that originated south of the Bahamas On October 9, 1975, an individual was characters are on the dorsal surface, two days previously. On July 3, 1973a found sick on a beach near Jacksonville, whereasflying tropicbirdsare normally moribund Red-billed Tropicbird was re- Florida. On May 16, 1979, Lee collected seen only from below, the likelihood covered from a tenth floor window two specimens ca. 40 miles east of that some previous records were ledge in Providence, Rhode Island Oregon Inlet, Dare County, North Car- misidentified becomes even greater. (Finch 1973)and the specimenis now at olina, and on September 1, 1979, a sick Red-billed Tropicbirds are pantropi- the Museum of Comparative Zoology, Red-billed Tropicbird was found cal and range in the Pacific to southern Harvard University. Three records ex- beached near Stuart, Martin County, California between Long Beach and ist for Florida. The first is a sight record Florida. These birds represent the third Catalina Island, near San Clemente Is- by J. Johnsonon July 9, 1964, 31 miles through sixth documented records of land, off San Diego (A.O.U. Check-list off Cape Canaveral (Stevenson 1964). the speciesfor eastern North America. 1957). In the North Atlantic they are Additionally a photo record at the known to breed only as far north as the HEFIRST FLORIDA specimen record North Carolina State Museum of Natu- Virgin Islands but are reliably reported nd third for the eastern United ral History (hereafter, N.C.S.M.) is ranging north to the Bahamas, at least States, was of a sick bird found by Ron available for May 1981. to Latitude 23øN, in the nonbreeding Davin at Ponte Vedra Beach, St. Johns Details on these occurrences are pre- season. White-tailed Tropicbirds nest County, south of Jacksonville Beach, sented below. Such evidence of Red- throughoutthe Caribbean and Bahamas October 9, 1975. The bird, an adult billed Tropicbirdsin this region suggests as well as on Bermuda at Latitude 32øN female, was held captive by Mrs. Vere that someof the sightrecords for White- and are reliably documented as ranging Brumbaugh, Jacksonville, until it d•ed tailed Tropicbirds, Phaethon lepturus, north in the western Atlantic to North January30, 1976.The specimenis in the may be suspect. There is little value in Carolina near the coast and even farther collection of the Florida State Museum questioning earlier identifications, but north in the Gulf Stream, or east of it, (F.S.M. 19291). It had no apparent molt we take this opportunity to briefly re- with records of accidentals as far north and weighed 496 grams; primaries and view the nature of tropicbird records as Nova Scotia. tail feathers were badly frayed and from eastern North America, including worn from two months' captivity. Mea- the upper Gulf of Mexico, and to dis- Peters and Burleigh (1951) and the surements: right wing chord 250 mm, cuss the more obvious field identi- A. O. U. Check-list (1957) recorded left chord 270 mm, culmen 64.2 mm, fication problems. Red-billed Tropicbirds from the New- tarsus 26.3 mm. The second Florida Althoughnumerous reports of tropic- foundland banks based on P. E. Freke's specimen and sixth for the eastern birds, chiefly ofWhite-taileds, are avail- assertion that he "noticed" this bird United States, was of a bird found mori- able from the western North Atlantic there in August 1876. Palmer (1962) bund on the beach a meter or so south of and Gulf of Mexico, few are supported found this record unsatisfactory, and the St. Lucie-Martin County line on by specimensor photographs.Until re- Godfrey (1966) considered the bird's September1, 1979•just ahead of hum- cently (see Peterson 1980) the White- occurrence in Canada hypothetical. cane David, which passedthrough the tailed Tropicbird was the only tropic- The first specimen record of the Red- area on September 3--by a Mrs. Patter- bird recognizedin popular field guides billed Tropicbirdfor continentaleastern son, who transported it to Ms. Jean as occurring in this area. This had the North America was of an immature Henry, Martin County Audubon Wild- effect of leading observersto the belief female (A.M.N.H. 776556) found dead life Hospital. It died there several days

Volume 35, Number 6 887 later. One tail streamer, 130-150 mm mens. Two cestodes(Tetrabothrins sp.) were sible second Bermuda record was seen long, broke off and was lost during found in the intestines. Tetrabothrinsrnagel- by Wingate September 11, 1979 in the !anicus has been reported for the Red-tailed captivity. The specimen,a female, is at Tropicbird, P. rubricaudus, in the Indian wake of hurricane David. The bird ap- the University of South Florida (G. E. Ocean (Deblock 1966). Mercury concentra- peared very large with a slow wingbeat Woolfenden 5223). Measurements: tions (ppn wet weight) were .66 and .78 in the and barred upper plumage, but as it wing chord 295 mm, culmen 59 mm, muscleand .75 and .59 in the kidney, respec- lackedelongated tail feathers, the possi- tarsus 28.8 mm, ovary 11 x 2 mm. The tively, for the adult and immature birds. bility of confusion with an immature P. Mercury was not present in the liver. This emaciated bird contained no fat and sp.ecies apparently does not regulatemer- lepturus recently departed from a nest weighed 350 grams. The skin and body cury ingestedwith its food. The kidneys of cannotbe discounted.This is especially skeleton were saved. Mallophaga birds properly regulating mercury levels true becausethe bird was sightedinside present were Ishonecra: Saernundsso- should have concentrations much higher CastleHarbour, where a vagranttropic- than the muscle. Investigations of other sea- nia phaetona. birdsgenerally show higher metal concentra- bird would not normally be expectedto The two North Carolina birds col- tions in older birds (Whaling et al. 1980). occur. lected May 16, 1979 both approached The "normal" season of occurrence the charter boat "Gal-O-Mine" in direct PHOTOGRAPHRECORD of an adult of P. lepturus in North America is line flights at approximately 35-40 feet Red-billedTropicbird was obtained difficult to assessowing to the occur- above the surface of the sea, then hov- by Wayne Irving 0N.C.S.M.) May 6, rence of numerous storm-driven birds ered as if to land on the boat's observa- 1981. The single bird flew around the and the possibility of confusion with P. tion tower. The first bird, observed headboat"Captain Stacey" in the Gulf aethereus which partly mask extreme at 0945, was an immature female Stream offMorehead City, North Caro- dates of occurrence. We think it proba- (N.C.S.M. 7183) with the following lina. Beyond the continental shelf, P. ble, however, that the early June to data: weight 607.8 grams, gonads2 x 8 aethereus has now also been recorded mid-Septemberdates reported by Lee mm, total length 480 mm, wingspan from Bermuda at 32ø18'N, 64ø45'W. An and Booth (1979) may be typical for all 1033 mm, wing chord 317 mm, tail 130 earlier sightrecord from Bermuda (Ver- areasexcept southTexas and Florida. It mm, tarsus 33 mm, body temperature rill 1901) has been rejected (by us) as appears that the majority of coastal P. 38.5øC.The primaries looked worn and unreliable on the basis of many proven lepturusrecords from north of the Caro- the innermost ones were new, just be- errors in A. Hyatt Verrill's Bermuda litms are of true vagrant and/or storm- ginning to emerge from the sheaths. identifications. On June 8, 1968, driven individuals. From North Caro- Thus, although the bird was obviously Wingate obtained and prepared as a lina south, the bird's status would sub-adult, based on its yellow bill and specimenan immature female P. aethe- probably best be described as expected lack of "streamers", the molt and con- reus that had beached on Elbow Beach, but uncommon. Lack of systematicoff- dition of feathers indicated it was past PagetParish, Bermuda, in starving con- shore surveys throughout much of the its first year. The second specimen, dition with an eye injured or diseased area, however, make this statement collected at 1005, was an adult female (ova minute, no weight taken). A pos- somewhat speculative. with a red bill and full streamer (N.C.S.M. 7182) with these data: weight 624.9 grams, gonads 2 x 10 mm, total length 905 mm, wingspan 1033mm, wing chord 317 mm, tail 539 mm, tarsus 35 mm, body temperature 40.0øC. No molt was observed, but the central tail feather was still partly ensheathed. George Watson of the United States National Museum, exam- inedboth specimensand concludedthat they were Phaethon aethereus meso- nauta, the race that breeds in tropical parts of the North and mid-Atlantic. Two large flying fish (Exocoetidae; probably Cypselurus), along with par- tial remains of other unidentified fishes, were removed from the stomach of the immature bird. The stomach of the second bird contained no recognizable food items because it apparently regur- gitated during collecting.

The following external parasites were identified: Mallophaga Amblycera: Austro- tnenopan(probably beckii see Timmermann 1954) and Acarina: Allotidae Latnina!!optes phaetontis.Phaethon aethereusis known to host at least two other specieswhich were not recovered from the North Carolina speci- Figure1. Phaethonaethereus adult (N.C.S.M. 7182)upper and lepturus adult (N.C.S.M. 6828).

888 American Birds, November 1981 close range and also are difficult to see becausethey involve the dorsal surface (Figs. 1-2). Nevertheless, under good light conditions the wings have a trans- lucent quality, thus the black tertials and secondary coverts of P. !epturus can be seen from below as very dark shadows. The barring of the dorsal plumageofP. aethereusat all stages,is much finer and denser than that of immature P. lepturus, which is coarse and sometimes widespaced. The dorsal as- pect of immature P. lepturus should therefore appear distinctly barred at any distance, whereasP. aethereus may appear to be a uniform pale gray when viewed from afar. The presence of barring on any tropicbird with elongated central tail feathers automatically confirms its identity as P. aethereus, because adult P. lepturus are never barred. An illustration of the difficulty in- volved in separating the two species is seen by the single Phaethon "specimen" record reported as P. lepturus by Pearson et al. (1942) for North Caro- lina. According to the description of the bird, found dead on the beach on July 5, 1939, it "was in immature plumage, as the back was fully barred with wavy, black lines. The long, central tail feathers worn by the adults also were absent." The original record card in the museum files said it was an adult. In view of the information discussed above, we must questionthe validity of this identification since the description could refer to either species. A photo- graphreportedly taken of the specimen, and the salvaged skull, apparently no Figure 2. From left to right: adult and immature Phaethonaethereus. longer exist. Most eastern North Amer- ica sight records do not contain any Adult tropicbirds can readily be rec- until they are relatively close to the descriptionsother than the presence of ognizedeven at some distanceby their boat. They are more likely to be heard long central tail feathers. We hope that "streamered" tails. At distances where before they are seen. future bird studentswill attempt to iden- their tails are not evident, or in the case tify and report field characters. of immature birds, their long, pointed HELARGER SIZE, slightly broader Lee (1979) suggestedthat the inner wings, bill, and tail are suggestiveof a ngs, and slower wingbeat of P. edge of the Gulf Stream and the edge of large tern in flight. The tropicbird's aethereus make it comparable to a the continental shelf in the Hatteras- rapid, steady, deep wingbeat, however, Royal Tern in flight. In contrast, the Oregon Inlet area of North Carolina should separate it from any gulls or smaller P. lepturus has narrower wings provide an area of regular seabird con- terns expected in North American wa- and faster wingbeat (slightly faster than centrations, at least during warmer ters. Tropicbirds normally occur singly a Common Tern). Bill color is unreliable months. The regular occurrence here of except near their breedinggrounds. Our as a field mark because of extreme "unexpected" birds indicates that experiences, and first-hand reports individual and age variation, and be- many of them are not simply vagrants. from charter boat captains, show that cause it is difficult to see accurately Diversity and modest densities have the birds frequently follow boats and when being viewed from a rolling boat. been documented, with over a third of seem to be attracted to those with high Immatures of both specieshave yellow- the known pelagic fauna "discovered" rigging, over which they hover as if to ish bills that change gradually to red in in the last several years (Lee and Booth land. Because of their light ventral sur- P. aethereus, and to orange or orange- 1979, Lee and Rowlett 1979). Lee and face and their high (30-200 feet), direct red in breeding P. !epturus. Differences Platania (1979) have since discovered flight, individuals are often not seen in plumage pattern are useful only at probable sightings of five additional

Volume 35, Number 6 889 LITERATURE CITED

AMERICAN ORNITHOLOGISTS' UN- ION. 1957. Check-list of North American Birds. 691 pp. BULL, J. L. 1964. Red-billed Tropicbird on Long Island, New York. Auk 81 (3): 433- 434. DEBLOCK, S. 1966. Six cestodes d'oiseaux de mer ou de xivage de l'hamisphere Austral (ile Europa). Description de Tetrabothrius mozambquus, Baebonaia baerbonae. Mere. Mus. Nat. Hist. Paris No, S.A., r. 41 (1): pp 127-134. FINCH, D. W. 1973. The Nesting Season-- Northeastern Maritime Region. Am. Birds 27(6): 1020. GODFREY, W. E. 1966. The Birds of Can- ada. Nat. Mus. Canada Bull. No. 203, Biol. Ser. 73:1-428. LEE, D. S. 1979. Second record of the South Trinidad Petrel (Pterodroma arminjo- niana) for North America. Am. Birds 33(2): 138-139. --and R. A. ROWLETT. 1979. Additions to the seabird fauna of North Carofina. Chat 43(1): 1-9. -- and J. BOOTH, JR. 1979. Seasonal distribution of offshore and pelagic birds in North Carolina waters. Am. Birds 33(5):715-721. --and S. P. PLATANIA (1979). Unverified sight records of sea birds in North Caro- lina waters. Chat 43(4): 79-81. PALMER, R. S., ed. 1962. Handbook of North American Birds. Vol. 1. Loons through Flamingos. Yale Univ. Press, New Haven. 567 pp. PEARSON, T. G., C. S. BRIMLEY, and H. H. BRIMLEY. 1942. Birds of North Carolina. N.C. Dept. Agric., Raleigh. 434 PP. PETERSON, R. T. 1980. A Field Guide to the Birds East of the Rockies. Houghton Mifflin Company. 384 pp. PETERS, H. $. and T. D. BURLEIGH. 1951. The birds of Newfoundland. New- foundland Dept. Nat. Res., St. John's. 431 pp. STEVENSON, H. M. 1964. The Nesting Season--Florida Region. Aud. Field Figure 3. Adult and immature P. lepturus. Notes 18:503. TIMMERMAN, YON G. 1954. $tudien Uber Mallophagen Aus Den $ammlungen species. Because of these findings, it in Florida. Cooperation of the charter- Des Britischen Museums (Nat. Hist.) would be premature to assumethat oc- boat captains of Oregon Inlet, North London. Bonn Zool. Beitr 5:195. currences such as those reported here Carolina, is greatly appreciated.Steven VERRILL, A. H. (1901). Notes on birds of for the Red-billed Tropicbird represent P. Platania, Ron Mobley, John Funder- the Bermudas with descriptions of two new subspeciesand several additionsto nothing more than vagrants. Other burg (all N.C•S.M.), and CaptainAllen the fauna. Osprey 5:82-85. coastal areas of eastern North America Foreman were present on the May 16 WHALING, P. H., D. $. LEE, J. have not been as intensively surveyed, trip. George Burgess confirmed our BONAVENTURA, and M. RENTZE- so the absence of records of various identification of the food items; Ron PI$. 1980. The body burden approach of looking at natural mercury accumulation pelagics there has less meaning at this Mobley provided identification of the in pelagic seabirds, 1980stated meetingof time, internal parasites; Mike Browne (N.C. the American Ornithologists' Union. State University) and K. C, Emerson ACKNOWLEDGMENTS (U.S,N.M.) identified the external par- North Carolina State Museum, P.O. asites; Patrick Whaling (Duke Univer- Box 27647, Raleigh, North Carolina E THANKRenaldo G, Kuhler, sity Marine Laboratory) provided the 27611 (Lee), Department of scientific illustrator, N.C.S.M., data on the heavy metal concentrations; Agriculture and Fisheries, P,O. Box for preparingthe figuresaccompanying and John E. Cooper (N.C.S.M,) re- 834, Hamilton, 5, Bermuda (Wingate), this article. viewed earlier drafts of the manuscript. Florida Audubon Society, 35 1st Court Lyn Atherton, Tampa, Florida pro- This is publication 1981-13of the North S. W., Veto Beach, Florida 32960 vided useful information on Phaethon Carolina Biological Survey. (Kale).

890 American Birds, November 1981