Population Estimates, Conservation Concerns, and Management of Tropicbirds in the Western Atlantic

DAVID S. LEE1 AND MARTHA WALSH-MCGEHEE2

1North Carolina State Museum of Natural Sciences, P.O. Box 29555, Raleigh, N C, 27626, USA. [email protected] 2Island Conservation Effort, P.O. Box 599 Windwardside, Saba, Netherlands Antilles. [email protected]

ABSTRACT.—Two species of tropicbirds (Phaethontidae) live in the Western North Atlantic. The White- tailed Tropicbird of the region is an endemic race, Phaethon lepturus catesbyi, with approximately 5000 pairs. This is half the estimate made less than two decades ago. The Red-billed Tropicbird, P. aethereus, has approximately 2000 pairs regionally and fewer than 8000 pairs globally. Neither species has been considered to be of conservation concern. We suggest that the Atlantic populations of Phaethon lepturus and the global population of Phaethon aethereus be considered for appropriate conservation status listings reflecting their rare and declining populations.

INTRODUCTION 30 colonies), and was formerly reported as breeding off Ecuador and Peru. The same Two of the three extant species of tropic- race also breeds in the Cape Verde Islands birds (Phaethontidae), the White-tailed (less than 1000 pairs and perhaps as few as Tropicbird (Phaethon lepturus) and the Red- 100 pairs), islands off Senegal (status un- billed Tropicbird (Phaethon aethereus), occur known) and the Madeleine Archipelago of in the Atlantic (AOU, 1998). A large per- Senegamba (30 pairs). Furness and Mon- centage of the Atlantic breeding popula- teiro (1995) record a single breeding pair of tions of both species nests in the West In- Red-billed Tropicbirds in the Azores, the dies region. first European breeding record and the The Western Atlantic population of only example of a range expansion in this White-tailed Tropicbirds is represented by species. Van Halewyn and Norton (1984) an endemic subspecies (P. l. catesbyi) whose estimated the West Indian population at breeding distribution extends from Ber- 1600 pairs at 22 sites. muda and the Bahamas, through the We review the distribution, abundance, Greater and the northern Lesser Antilles, breeding, and conservation status of these and reportedly, to Trinidad and Tobago two pelagic seabirds in the Western North (AOU, 1998). In the early 1980s, the total Atlantic and discuss possible management population was estimated at more than strategies. 10,000 pairs breeding at over 30 sites (van Halewyn and Norton, 1984) but since then no additional information has appeared. MATERIALS AND METHODS We have reassessed the population status of this species in the western North Atlantic For historical records we relied on exist- and find the aggregate population to be sig- ing literature and on data from museum nificantly lower than previously reported. egg collections. Information compiled is Red-billed Tropicbirds in the Atlantic are derived from the previous two decades, the represented by the subspecies P. a. meso- greater portion from the 1990s. On islands nauta. This race breeds in the Lesser An- with scant recent information, historical re- tilles and southern Caribbean, the Gulf of ports always indicate small colony sizes. California (350 pairs at 2 colonies), the Whenever possible, population estimates Galapagos Islands (a few thousand pairs at are based on personal observations, re- 267 268 D. S. LEE AND M. WALSH-MCGEHEE cently published reports and information Tropicbirds from known nest locations vis- given to us by resident authorities. We be- ited many occupied and unoccupied holes lieve that we have up-to-date information in the course of a morning. This behavior on the species conservation status and local has been observed occasionally in Red- population sizes for all countries except billed Tropicbirds on Saba (pers. obser.). several Lesser Antillean islands, where the The problems in obtaining comparable populations of both species are believed to population estimates are compounded by be small (Montserrat, St. Lucia, and St. Vin- the lack of a central seabird information cent & the Grenadines). base, contact persons for a number of is- The aggregate population figures we lands, and the multinational makeup of the have determined for both species in the re- region. Censusing and estimation methods gion probably err on the high side. The vary. Many nesting sites are remote and only portion of the West Indies where size- seldom visited, and those visited by seabird able populations of White-tailed Tropic- students are often visited at times when birds may remain undetected is the keys terns and other species are in peak breed- along the northern coast of Cuba. While it ing numbers (usually a poor time to esti- would be surprising if these birds did not mate tropicbird population sizes). A num- breed there, recent surveys (H. Gonzalez, ber of early surveys failed to differentiate pers. comm.) give no indication that they the two species or have misidentified them. do. Population numbers and the identifica- Numbers of nesting pairs (Table 1) were tion of colony sites for Red-billed Tropic- obtained from literature, personal observa- birds are less well documented than those tions, and the observation of others. In all for White-tailed Tropicbirds because many cases, we have attempted to cite the most island groups in the Lesser Antilles are sel- recent source. Field observations are listed dom visited by biologists, and because of in ascending order of reliability; estimates, the unknown sizes of the small, scattered surveys, censuses, and counts. breeding colonies on the northern South American and eastern Central American RESULTS coasts. Estimating the sizes of breeding tropic- The following is a compilation of the sta- bird populations is difficult. Major prob- tus and conservation concerns for White- lems include an inability to access colonies tailed and Red-billed Tropicbirds in Ber- or vantage points from which to observe muda, the United States, the Bahamas, the and count birds, and the optimal timing of Greater and Lesser Antilles, Trinidad & To- visits, both seasonally and hourly. Bird bago and the Caribbean coast. Population numbers are variable, and behavior causes estimates of both species are presented in problems because birds are not always pre- Table 1. sent on the nests and the intervals between the changing of incubation partners or Populations: status and trends feeding of chicks may last several days. Wingate (pers. comm.) believes that the Bermuda: White-tailed Tropicbird.—The number of nesting pairs of White-tailed largest Atlantic population of this species Tropicbirds at any given location in Ber- breeds on Bermuda. After reviewing the muda is six times the maximum number of historical records, D. B. Wingate (pers. birds seen in the air. This factor would not comm.) has documented a drastic decline. necessarily work for other populations, Partially due to millinery use, the tropic- where feeding grounds may be closer or birds were afforded full legal protection by foraging grounds may be richer. While the Wild Birds Protection act of 1881. Nev- birds seen entering nesting holes clearly in- ertheless, since the 1920s the species has dicate local nesting activity, a tally of the continued to decline steadily. It is esti- number of holes visited does not necessar- mated that in 1950 there were 3000 pairs ily equate to the total number of active nesting in Bermuda, but this number was nests. In the Bahamas, marked White-tailed reduced to 2500 by 1995 (D. B. Wingate, TABLE 1. Population estimates for two species of tropicbirds (Phaethon) in the western North Atlantic. Symbols: — = absent: b = breeding (population size unknown): b? = breeding suspected:f=fossil record only: e = extirpated in historic period: e? = believed extirpated. Numbers indicate breeding pairs. Percentage numbers are for total Western North Atlantic populations.

Breeding location White-tailed Red-billed Source Census methods Bermuda 2500 (45%) — Lee and Walsh-McGehee, 1998 Surveys Bahamas 1000 (19%) — Walsh-McGehee et al., 1999 Literature reviews and surveys United States Dry Tortugas 0-2 (0.1%) — Stevenson and Anderson, 1998 Count Greater Antilles Cuba >100 (2%) — Vinã et al., 1998 Surveys Jamaica 50-100 (2%) — A. Haynes-Sutton Surveys RPCID NWSENALNI 269 ATLANTIC WESTERN IN TROPICBIRDS Cayman Islands 60 (1%) — P. Bradley, pers. comm. Count Hispaniola 1000 (19%) — J. Ottenwalder, pers. comm. Estimate Mona & Monito 100-200 (3%) — J. Saliva, pers. comm. Census Puerto Rico 200-300 (5%) <10 (1.4%) J. Saliva, pers. comm. Census U.S. Virgin Islands <40 (0.1%) 300 (14%) J. Pierce, pers. comm. Count British Virgin Islands <50 (0.1%) <100 (5%) J. Pierce, pers. comm. Count Lesser Antilles Sombrero — b? van Halewyn and Norton, 1984 Literature review Redondo b? c. 100 (5%) van Halewyn and Norton, 1984 Literature review Antigua f c. 50 (2%) K. Lindsay, pers. comm. Observation Barbuda c. 10 (0.2%) 50-100 (5%) K. Lindsay, pers. comm. Observation St. Maarten 15 (0.3%) 15 (7%) van Halewyn and Norton, 1984 Literature review Saba 50-100 (2%) 750-1000 (35%) M. Walsh-McGehee, pers. comm. Survey-island Count-10% St. Bartholomew — e Van Halewyn and Norton, 1984 Literature review St. Eustatius >10 (0.2%) 30 Voous, 1983 Survey Montserrat —? c. 100 (5%) J. Daley, pers. comm. ? Guadeloupe 68 (1.2%) 69 (3%) Guadeloupe WIldlife Dept., pers. comm. Census Dominica 10+ (0.2%) e R. Winston, pers. comm. Observation Martinique c. 10 (0.2%) c. 50 (2%) van Halewyn and Norton, 1984 Literature review St. Lucia ? ? Evans, 1990 ? St. Vincent b? e? Evans, 1990 ? Barbados — e P. A. Buckley, pers. comm. Recent observation Grenadines e b Evans, 1990 ? Trinidad & Tobago — c. 400 (20%) Van Halewyn and Norton, 1984 Literature review Caribbean Basin — c. <100 (5%) van Halewyn and Norton, 1984 Literature review Total c. 5500 c. 2200 270 D. S. LEE AND M. WALSH-MCGEHEE pers. comm.). Development in outlying ar- (1984). Vinã et al. (1998) present evidence of eas and increased predation from pet cats a slightly larger area of distribution along and dogs has accelerated the species de- the southeastern coast in the early 1900s. cline (Wingate, 1988). There is some indication that the species Bahamas and the Turks & Caicos: White- may breed on the cays of the north coast tailed Tropicbird.—Walsh-McGehee et al. (Morales Leal and Garrido, 1996) but this (1999) identified 36 historic and extant remains to be validated. Despite seemingly breeding colonies of White-tailed Tropic- appropriate cliff habitat on the Isle of Pines, birds in the Bahamas archipelago. There residents interviewed by Lee in January are no documented island extirpations. 2000 indicated that the birds are not breed- Several sites identified by Bryant (1859) ing there. have not been revisited and the bird’s sta- Jamaica: White-tailed Tropicbird.—Van tus on those islands is unknown (Sprunt, Halewyn and Norton (1984) reported 200- 1984). To compensate for the fact that some 1000 pairs nesting in Jamaica. Haynes- nesting sites may remain undetected, Sutton (pers. comm.) reports 10 active colo- Walsh-McGehee et al. (1999) provided high nies with a total population of 50-100 pairs. population estimates (pr./site) for all Cayman Islands: White-tailed Tropic- known extant sites, estimating a total of bird.—Nesting is confined to the Bluff on fewer than 1000 breeding pairs of White- Cayman Brac and the south coast of Grand tailed Tropicbirds for all islands in the ar- Cayman (Bradley, in litt.). The colony on chipelago. This figure agrees closely with Grand Cayman has 18-20 pairs. The bird earlier and current estimates made by was an abundant breeder on Cayman Brac, Sprunt (1984 and pers. comm.). Following where a sizeable colony was documented Bermuda, the Bahama archipelago is the by Maynard in 1889. About 400 pairs bred second most important island group for on this island in the early 1980s, but by 1995 breeding White-tailed Tropicbirds in the numbers fell to 40 pairs (P. Bradley, in litt.). western North Atlantic. By 1998 numbers had not recovered. Fossils United States: White-tailed Tropicbird.— were found on Cayman Brac by Morgan This species is not known to breed in the (1994). United States, although between 1974 and Hispaniola: White-tailed Tropicbird.—Jose´ 1984 one or two pairs were seen in court- Ottenwalder (pers. comm.) has estimated ship flight and in incubation positions at Ft. the total population at 1000 pairs. Specific Jefferson, Dry Tortugas (Florida Keys) nesting localities are largely undocu- (Stevenson and Anderson, 1994). This is the mented. Haiti: The U.S. National Museum only instance of attempted colonization of a of Natural History (USNM) has two speci- new site documented for this species. mens collected in 1931 by A. Wetmore at Ile-a`-Vache. No other breeding localities are mentioned in the literature. Biologists Greater Antilles working in the country agree that there has been a general loss of breeding sites and a Cuba and Isle of Pines: White-tailed Trop- reduction in the overall population (F. Ser- icbird.—Vinã et al. (1998) provide the only gile, pers. comm.) but this has not been up-to-date summary of tropicbird nesting documented. Dominican Republic:de in Cuba. They found that nesting was re- Dod (1981) indicates that the species breeds stricted to two or three small areas, and only on the easternmost third of the coast conclude that the total population is fewer and on a section along southwestern coast. than 100 pairs. Documented nesting is lim- Beata, Alto Velo, and Saona are extant ited to a small area along the southeastern breeding sites (J. Ottenwalder, pers. coast, at sites where the species was first comm.), but colony sizes are unknown. A noted by Gundlach in the 1800s and last colony of 20-25 pairs nests at Cabo Cabroń, reported by Barbour (1943). The actual at Las Galeras, east of the Samana´ penin- nesting area is about one third smaller than sula. A colony of 60 pairs nests southwest indicated by van Halewyn and Norton of Cabo Rojo and the Bahıá de Las A´ guilas. TROPICBIRDS IN WESTERN ATLANTIC 271

Mona and Monito: White-tailed Tropic- Rock, Cockroach, Cricket, Dog, Dutchcap, bird.—The USNM has birds collected in Flanagan, and Frenchcap Cays. Red-billed 1935 by J. Smyth and S. T. Danforth at Tropicbird. Based on a nest count of 225, J. Playa de Pa´jaros (Mona). Van Halewyn and Pierce (pers. comm.) estimated a maximum Norton (1984) estimated the population of of 300 pairs. Most nests were found on these islands at 1000 pairs but current esti- Cockroach Cay, followed by Hans-Lollick, mates by the US Fish and Wildlife Service Mingo, Congo, Kalkun, Buck, and Capella stand at 100-200 pairs. The large difference Cays. Fewer nests were found on Carval in estimates is believed to reflect errors in Rock, Cas, Cricket, Dog, Dutchcap, Flana- earlier calculations and is not interpreted as gan, Flat, French Cap, Grass, Inner Bass, a major population decline. Little St. James, Outer Bass, Ram’s Head Puerto Rico: White-tailed Tropicbird.— (St. James), Saba, Sail, Savannah, Shark, These birds were apparently common early Sula, Two Brothers, Water Island, West, in the 1900s along cliffs on the north and and Whistling Cays. One adult was seen south coasts of western Puerto Rico, but are searching for a nest on Hassel Island. Red- now limited to a few nesting pairs on the billed Tropicbirds may nest in very small northwest coast (van Halewyn and Norton, numbers on the main islands of St. Thomas, 1984). Schaffner (1988) reported a mini- St. John, and St. Croix. They formerly mum of 63 nests on the Culebra archi- nested on Little Flat Cay. The Western pelago in 1984 and implied that current Foundation of Vertebrate Zoology (WFVZ) populations may be similar to those ob- collection has an egg from Cas Cay (31 served by Wetmore during April 1912 March 1936). (Wetmore, 1917). Gochfield et al. (1994) re- British Virgin Islands: White-tailed Trop- ported that this population declined to icbird.—J. Pierce and E. Schreiber (in litt.) fewer than 3 pairs by 1987. Nesting takes estimated 20-50 pairs at Fallen Jerusalem, place on Vieques (less than 10 pairs), on Great Tobago, Guana Island, and Norman Culebra at Cayo Lobos, Cayo del Agua, Island. The USNM has a specimen from To- Cayo Luı´s Penã, Cayo Molinos, Cayo bago Island collected by G. Seaman in 1951. Norte, and Punta Soldado (40 pairs), and Red-billed Tropicbird. J. Pierce and E. on mainland Puerto Rico at Quebradillas. Schreiber (in litt.) estimated 80-100 pairs at Contrary to van Halewyn and Norton Cockroach Cay, Dog Islands, Fallen Jerusa- (1984) the species currently breeds on the lem, Great Tobago, Little Tobago, Green south coast at Caja de Muerto, just off Cay, Guana Island, and Norman Island. Ponce. Red-billed Tropicbird. Van Halewyn and Norton (1984) report at least one pair of Lesser Antilles birds and one former colony on the south coast of Puerto Rico. The species breeds at White-tailed Tropicbird.—Nesting is con- seven sites on Vieques and Culebra (Cayo fined mostly to the northern islands, with Lobito, Cayo Alcarraza, Cayo Ratoń, Cayo Martinique being the southernmost known Luis Penã, Cayo Norte, Cayo Molinos, and breeding site. Islands which do not support Cayo Geniquı´). Total population size is un- nesting birds include Anguilla, Antigua, known. Aves Islands, Barbados, Bequia, Carriacou, US Virgin Islands: White-tailed Tropic- Desirade, Dod Island, Grenada, the Grena- bird.—J. Pierce (pers. comm.) estimates dines, Hat Island, Les Saintes, Marie Gal- more than 40 pairs distributed in small ante, Scrub Island, Sombrero, St. Bartho- colonies of 3-10 pairs on five islands. Ni- lomew, St. Kitts-Nevis, St. Lucia, and St. chols and Bond (1943) found 20 nesting Vincent. Wilson (pers. comm.) indicates pairs at Cas Cay, much higher than num- that local fishermen have observed some bers seen there today (J. Pierce pers. nesting tropicbirds on St. Kitts but it is un- comm.). The species formerly bred on clear which species is involved or whether Whistling Cay and it now breeds on Cas, the colony is still extant. Congo, Hans-Lollick, Outer Bass Cays, and Red-billed Tropicbird.—This species breeds Water Island. It may also breed on Carval or has bred on all major islands in the Lesser 272 D. S. LEE AND M. WALSH-MCGEHEE

Antilles. There is currently no nesting on Bar- obser.) estimates the current population at bados (P. A. Buckley, pers. comm.). 50-100 breeding pairs. Numbers have de- Sombrero: Red-billed Tropicbird.—Van clined apparently a result of expanding Halewyn and Norton (1984) reported nest- Red-billed Tropicbird populations. Breed- ing on this island but recent surveys (J. ing has been recorded at Flat Point, Cove Pierce, pers. comm.) suggest that the colony Bay, Fort Bay, and Ladder Bay. Red-billed is not extant. Tropicbird. The USNM has a series of skins, Redondo: White-tailed Tropicbird.—Van including downy young, collected in 1937 Halewyn and Norton (1984) reported nest- by S. T. Danforth at Booby Hill and Little ing on this island but the species was not Booby Hill cliffs (both current nesting reported by K. Lindsay (pers. comm.). Ei- sites). Walsh-McGehee (pers. obser.) indi- ther earlier information was in error or the cates that breeding activity occurs through- species no longer breeds there. Red-billed out the year, and that there is multiple use Tropicbird. There may be more than 100 of some nest sites. An estimate of 750-1000 pairs (K. Lindsay, pers. comm.). nesting pairs was made by detailed nesting Antigua: White-tailed Tropicbird.—This density studies in one sub-colony, extrapo- species is known from a late Holocene ver- lating colony size based on comparative tebrate fossil deposit at Burma Quarry (Pre- numbers of flying adults at inaccessible gill et al., 1988) and is assumed to have bred colonies, and considering the multiple-use on the main island. Bird Island, off Anti- of nests resulting from year-round breed- gua, has 8-12 pairs (1973-83; P. Bradley, ing. Breeding has been recorded at Flat pers. comm.). Red-billed Tropicbird. There Point, Cove Bay, Little Booby Hill, Booby are 6 pairs on Bird Island off Antigua (1973- Hill, Black Rocks, Tent Bay, Well’s Bay, 83; P. Bradley, pers. comm.). K. Lindsay Great Point, Sulphur Mine, and Green Island. (pers. comm.) estimated 50 breeding pairs St. Bartholomew: Red-billed Tropicbird.— on Antigua, with the largest population on Van Halewyn and Norton (1984) recorded Great Bird Island off the northeast coast. this species as a breeder but we have no Anguilla: Red-billed Tropicbird.—Van recent information and assume that the Halewyn and Norton (1984) reported this species no longer nests there. species as breeding on Anguilla but we St. Eustatius: White-tailed Tropicbird.—A have no recent information and assume few pairs were found breeding at Cupe that the colonies are not extant. Coy Bay (Voous, 1983). We assume a popu- Barbuda: White-tailed Tropicbird.—Van lation of fewer than 10 pairs. Red-billed Halewyn and Norton (1984) reported this Tropicbird. The USNM has three skins col- species as breeding on Barbuda but we lected by F. A. Ober in the 1800s. An esti- have no recent information and assume mated 30 pairs breed at Tumble Down Dick that the colonies are not extant. Red-billed Bay, Yenkin’s Bay, Gallows Bay, Cay Bay, Tropicbird. The USNM has two specimens White Wall, Venus Bay, and Concordia Bay collected in 1889 at Gun Shop Cliff, near (Voous, op. cit.). Two Foot Bay. K. Lindsay (pers. comm.) Montserrat: Red-billed Tropicbird.—The estimates between 50-100 pairs nesting on USNM has a series of skins collected in the sea cliffs on the eastern coast. 1938 by R. A. Tonge at Garabaldi Hill and St. Maarten: White-tailed Tropicbird.— at Rendezvous. Van Halewyn and Norton There are approximately 15 breeding pairs. (1984) questioned the occurrence of this Birds have been observed in a sea cave at tropicbird on Montserrat but Blankenship Maho Bay and probably occur at Mary’s (1990) considered both species of tropic- Point (Voous, 1983). Red-billed Tropicbird. birds as common residents. James Daley Voous (op. cit.) estimated the breeding (pers. comm.) estimated the total popula- population at 15 pairs (Pelican Key, Maho tion of Red-billed Tropicbirds at c. 100 Bay, and Mary’s Point). pairs. He reported breeding at Garabaldi Saba: White-tailed Tropicbird.—Voous Hill with additional small colonies from (op. cit.) estimated the breeding population Viewpoint north to the airport. According at only a few pairs. Walsh-McGehee (pers. to Daley, populations are dwindling. TROPICBIRDS IN WESTERN ATLANTIC 273

Guadeloupe: White-tailed Tropicbird.— nesting status. The USNM has a skin col- Reported as a breeder by Van Halewyn and lected by F. A. Ober in the 1800s. We do not Norton (1984). Unpublished studies con- know if colonies are extant. ducted in 1998 by Guadeloupe biologists Barbados: Evans (1990) considered estimated the total population at 68 pairs in White-tailed Tropicbirds as accidental and six colonies: Terre de Bas (26 pr), Terre de Red-billed Tropicbirds as formerly nesting. Haut (12), Cabrit (2), Grand Ile (6), Marie- Neither species nests on Barbados despite Galante (20), and Desirade (2). Red-billed the presence of cliff faces that could pro- Tropicbird. The USNM has skins collected vide good nesting sites (P. A. Buckley, pers. by F. A. Ober in the 1800s. Unpublished comm.). studies conducted in 1998 by Guadeloupe Grenadines: White-tailed Tropicbird.— biologists estimated the total population at Van Halewyn and Norton (1984) reported 69 pairs: Terre de Bas (2 pr.), Pointe des cha- this species nesting in the Grenadines, but teaux (20), l’Eperon (12), Marie-Galante (30). Evans (op. cit.) indicated it was absent. The Dominica: White-tailed Tropicbird.—The USNM has a specimen collected in 1937 by USNM has a specimen collected by D. Win- S. T. Danforth on Ramier Island. Red-billed gate in 1965 and the WFVZ has eggs col- Tropicbird. Evans (op. cit.) recorded the spe- lected in 1938 from near Petite Savanne. cies as nesting. The USNM has two col- Van Halewyn and Norton (1984) consid- lected in the Grenadines in 1937 by S. T. ered the breeding status as unknown and Danforth. One is from Ramier Island and assumed the species to be present in small the other from the western cay of Bequia. numbers. Evans (1990) reported the species Trinidad and Tobago: White-tailed Trop- as breeding on the island. Randolph Win- icbird.—Despite earlier reports (de Dalmas, ston (pers. comm.) reported the species as 1900; AOU, 1998) this species does not breeding on Dominica in the mid-1990s. breed on islands off Tobago. Its inclusion as The population is apparently small (less a breeding bird in the region is apparently than 10 pairs). Red-billed Tropicbird. Evans based on a misidentified specimen of P. (op. cit.) reported that the species occurs aethereus (ffrench, 1961). Red-billed Tropic- occasionally, but did not discuss breeding. bird. Van Halewyn and Norton (1984) esti- Randolph Winston (pers. comm.) reported mated 400+ nesting pairs based on it as formerly breeding on Dominica. ffrench’s (op. cit.) statement of 300 indi- Martinique: White-tailed Tropicbird.— viduals nesting at three sites off Tobago Van Halewyn and Norton (1984) consid- (Little Tobago, St. Giles, and Smith Island). ered the breeding status as unknown. Caribbean Basin: White-tailed Tropic- Evans (1990) reported nesting. The popula- birds are absent from the remainder of the tion is apparently small, probably less than Caribbean Basin. Red-billed Tropicbirds 50 pairs. Red-billed Tropicbird. Van Halewyn were reported from mainland Venezuela, and Norton (1984) reported this species but Los Testigos lslands, Los Hermanos Is- the population’s current status is unknown. lands, Los Roques Archipelago, and St. Lucia: Van Halewyn and Norton Panama (islands off Chiriqui Lagoon) by (1984) and Evans (1990) doubted if either van Halewyn and Norton (1984) and de species nested on the island. Shauensee and Phelps (1978). Birds may St. Vincent: White-tailed Tropicbird.—Van breed at La Orchila and Margarita (van Halewyn and Norton (op. cit.) were uncer- Halewyn and Norton, 1984). The aggregate tain if this species nested on this island, but population size is believed to be less than Evans (op. cit.) reported it as nesting. The 100 pairs. American Museum of Natural History (AMNH) has two eggs collected at Rock Fort on the south coast of St. Vincent (April DISCUSSION 1924). Red-billed Tropicbird. Van Halewyn Population sizes and Norton (op. cit.) recorded this species as nesting on St. Vincent but did not report Based on the information compiled here, colony size. Evans (op. cit.) questioned its the maximum western Atlantic aggregate 274 D. S. LEE AND M. WALSH-MCGEHEE breeding population for the White-tailed terial from the region was found by Mor- Tropicbird is 5000-6000 pairs. The number gan (1994) in the Caymans, where the of Red-billed Tropicbirds nesting in the species is extant, and by Pregill et al. (1988) West Indies and Caribbean Basin exceeds in Anguilla, where White-tailed Tropic- 2000 pairs and the total population for the birds no longer nest. There is no fossil re- subspecies indigenous to the region (P. a. cord of Red-billed Tropicbirds from the re- mesonauta of the Caribbean and eastern Pa- gion. cific) is estimated at 4000-5000 pairs. Previ- Using historical museum records, Walsh- ous surveys are few, incomplete, and often McGehee et al. (1999) have shown that unreliable. For most islands we have little White-tailed Tropicbird colonies have per- or no information concerning former abun- sisted at their current sites for at least a dance. We have documented declines in century and surely much longer. There is numbers of birds or breeding sites for Ber- no indication that sites are re-colonized muda, Cuba, the Cayman Islands, Puerto once they are abandoned. Except for the Rico, and Jamaica. Scott (1891) regarded one report from the Florida Keys, there is White-tailed Tropicbirds as common along no historic evidence of these birds coloniz- the entire north shore of Jamaica and re- ing new sites within their current range, or ferred to a population on the Pedro Keys. that this species has exhibited range expan- The species was obviously abundant at that sion since the late Pleistocene. However, time (he collected 25 adults on 25 and 26 the general absence of fossil tropicbirds February 1891) but Scott did not estimate from caves in Bermuda, in contrast to an the island’s total population size. However, abundance of fossil and sub-fossil Cahow it is clear that the species has declined dra- (Pterodroma cahow) material, suggests that matically over the last 100 years. The recent the White-tailed Tropicbird colonization of declines in the Cayman Islands, one of the that island has been relatively recent. few breeding sites with a well-documented history, are particularly alarming. Development Even before European contact, people colonizing islands had a major impact on Road construction and housing develop- seabird populations (Steadman, 1995a,b). ment have impacted tropicbird populations Steadman postulated that pre-European (Lee and Walsh-McGehee, 1998). The con- people may have been caused a 95 % re- struction of sea walls, filling in coastal duction in the number of seabirds on tropi- property, and the carving out of cliffs for cal islands. Tropicbirds, while not necessar- development have taken their toll on trop- ily eliminated from local faunas, became icbird populations. Tropicbirds have restricted to inaccessible sites. Post- mostly been reduced to nesting on inacces- European clearing of forests and the intro- sible sea cliffs and remote islands and cays. duction of feral animals further reduced Tourists are increasingly visiting small re- their numbers. It is important to note that mote cays, some of which are important tropicbirds do not require cavities in rocks seabird nesting islands. to nest. They have been documented as nesting under grasses and cedars in Ber- Contamination muda (Wingate, pers. comm.), and the smaller, more agile White-tailed Tropicbird Wingate (1978) estimated that the Ber- nests inland on forested islands in the Pa- muda tropicbird population has decreased cific, as well as in caves up to several kilo- by up to 40 % over the previous 25 years, meters from the coast (Lee, pers. obser; Lee due in part to pesticides. Thirty-one 19th and Walsh-McGehee, 1998). century-tropicbird eggs from Bermuda The fossil record sheds little information were compared with 10 broken eggshells on the former distribution and abundance collected in 1970. Measurements indicated of tropicbirds (see review by Lee and a significant 5.3 % pollutant-induced egg- Walsh-McGehee, 1998). Excluding the sub- shell thinning (James Wilson, unpub.). fossil records from Bermuda, the only ma- Wingate (1990) cited oil pollution as a TROPICBIRDS IN WESTERN ATLANTIC 275 contributing factor in tropicbird population ing sites. Wingate speculates that Hurri- decline. Tar balls from oil spills concen- cane Felix eliminated 30-50 % of the nesting trated in the Sargasso Sea and became en- sites along the south shore of Bermuda. At tangled in the flank feathers of tropicbirds other nests, storm surge removed all sand resting on the surface. The number of substrate from nest chambers, making White-tailed Tropicbirds exhibiting oil them temporarily unusable. A substantial fouling on arrival in Bermuda rose from 1 increase in nest site competition occurred in 100 in 1968 to about 1 in 15-20 in 1971 the following year. Indirect loss of popula- (Wingate, in Butler et al., 1973). In the early tions as a result of nest site destruction is 1970’s the ratio of oiled birds rose to 1 in 4. probably the most important long-lasting These birds failed to breed and disap- effect of hurricanes. peared from their nesting sites (Wingate, pers. comm.). Oil pollution peaked in the Predation from introduced animals Sargasso Sea around 1972 and began to de- Schaffner (1988) reported that black rats cline as a result of new regulations concern- were the most common cause of tropicbird ing dumping oil at sea. nesting failure at one of his study sites in Culebra Island, Puerto Rico. Black rat nest Disease predation was reported in Bermuda by Murphy (1936). Lee and Clark (1994) noted Observations of White-tailed Tropicbird a strong correlation between islands not oc- fledglings in Bermuda between 1958 and cupied by nesting tropicbirds and the pres- 1978 indicated that pox virus infections, al- ence of black rats in the Exumas (Bahamas). though generally of low prevalence, were Black rats have recently expanded their an important component of fledgling mor- populations and distribution on San Salva- tality, accounting for7%ofthenon-viable dor, Bahamas (Dougherty et al., 1997). The birds intercepted after departure from the rats were formerly confined to the interior nest. Only nestlings and fledglings were in- of the island in low densities, but are now fected, and the condition seemed invariably common in commercial areas and coastal fatal (Wingate et al., 1980). habitats. This change is thought to be a result of a newly developed resort on the is- Weather-related mortality land. It will be interesting, although perhaps predictable, to see how the coastal Mortality caused by hurricanes and other nesting population of White-tailed Tropic- major weather systems is largely undocu- birds responds to this change. Preliminary mented. White-tailed Tropicbirds are comparisons between 1997 and 1999 blown inland by storms in the SE United showed desertion of the more accessible States with a frequency that exceeds their nesting sites, but the total number of nest- proportionate abundance in relation to ing pairs was stable. In Bermuda, the other storm driven seabirds. However, brown rat occasionally takes tropicbird since the major tropical storm season oc- eggs and kills young chicks, but does not curs after the primary nesting season of normally occur in coastal areas, where nest- both tropicbirds, it seems that cyclones and ing takes place. Black rat predation of trop- other events impact only small popula- icbirds has also been reported in Bermuda tions. When hurricanes strike nesting areas (Murphy, 1936), as has predation by cats, during the late breeding season, there is dogs (the primary predator) and intro- some chick mortality from sea wash. Win- duced American Crows. Bartram reported gate (1995) reported that Hurricane Dean crows stealing chicks from nests as early as (August 6/7, 1989) and Hurricane Felix 1861 (Wingate, pers. comm.). (August 14/15, 1995) caused high loss of chicks and even brooding adults because at Predation from man least one third of the population was nesting when the storms hit Bermuda. More Man has clearly reduced the regional and importantly, storms may deteriorate nest- global populations of tropicbirds. As stated 276 D. S. LEE AND M. WALSH-MCGEHEE previously, pre-Columbian people had a rubble in nest cavities making them unus- major impact on seabird populations able. In Jamaica, traffic on adjacent roads (Steadman, 1995a,b). Before 1880, tropic- has caused the collapse of nest burrows (C. birds were hunted in Bermuda to supply Levy, pers. comm.). The construction of sea milliners with tail feathers. Egging, a com- walls and other forms of coastal develop- mon practice in some tropical seabird colo- ment often result in the loss of nest sites. nies, probably has little impact today on Occupation of nesting cavities by honey- tropicbirds due to the difficulty in access- bees or by nesting Barn Owls has been ing nest sites. Haynes (1987) reported ex- documented as sources of nest cavity loss ploitation of White-tailed Tropicbird eggs to tropicbirds on Bermuda. in Jamaica, but indicated that the local conservation status of the species was of no Availability of nest sites immediate concern. Wingate (pers. comm.) This is probably the primary factor lim- believes that the relative unpalatability of iting population expansion. On Bermuda, its meat and eggs favors survival in Ber- and probably elsewhere, the adult popula- muda. Walsh-McGehee et al. (1998) docu- tion exceeds the number of available pro- ment human consumption of White-tailed tected nesting cavities. The most common Tropicbirds in the Caicos Islands through causes of nest failure at one Puerto Rican the 1960s. On Saba, both species of tropic- colony was nest-site abandonment result- birds were taken for food until the early ing from agonistic encounters between con- 1950s. specifics during the early part of the breeding cycle (Schaffner, 1990). These Invasive exotics encounters often involved overt and severe fighting. Numerous failures have resulted Feral goats cause erosion through dam- from White-tails contesting nest site own- age to vegetation and displacement of ership in Bermuda. On Wardwick Wells rocks and soil while climbing on steep hill- (Exumas, Bahamas) White-tailed Tropic- sides. Early accounts of nesting White- birds nest not only on cliffs, but also com- tailed Tropicbirds indicated that they monly under rocks on the top of a plateau nested under grasses and other coastal veg- (Lee and Clark, 1994). We interpret this as a etation (Gross, 1912). One of us (MWM) response to a complete lack of introduced found a crushed tropicbird egg, only days predators on the island, and it is certain away from hatching, with the print of a that the population could be increased with baby goat hoof clearly visible. the provision of additional nesting shelters. In Bermuda, and probably elsewhere the Interspecific competition for nest sites is West Indies, naturalized Australian pines also a problem from Culebra southward (Casuarina equisetfolia) cause problems at through the Lesser Antilles. Red-billed cliff nesting sites. These trees become estab- Tropicbirds begin nesting months earlier lished on limestone cliffs and their roots than White-tails and have occupied most of may fill nest cavities. The trees are easily the nesting cavities before the arrival of the uprooted by storms, resulting in the de- smaller species. One of us (MWM) has seen struction of cliff nest sites. on Saba individual pairs of Red-billed Tropicbirds in the early phases of nesting Loss of nest cavities drive White-tailed Tropicbird pairs out of nest cavities. Interactions with Red-billed Natural erosion of cliff faces has caused Tropicbirds probably account for the rela- rock falls that have crushed nesting tropic- tive rarity of White-tailed Tropicbirds as a birds in Bermuda (Beebe, 1932; D. B. Win- nesting species east and south of Puerto gate, pers. comm.). Saliva (1989) and Wiley Rico. and Wunderle (1993) report negative effects on nesting habitat of White-tailed Management Tropicbirds on Culebra after Hurricane Management is hampered by a general Hugo. Hurricanes and other storms deposit lack of studies on both species of tropic- TROPICBIRDS IN WESTERN ATLANTIC 277 birds. Schaffner’s (1988) study of White- SUMMARY AND CONCLUSIONS tailed Tropicbirds in Puerto Rico provides None of the Western North Atlantic trop- the only quantitative data available for the icbird breeding populations is safe. Few West Indies. We are conducting similar colonies are in parks or other protected ar- studies of the Red-billed Tropicbirds on eas. Protective legislation is scant and en- Saba. Because of the remote nature of many forcement of existing legislation is often nesting colonies, many important sites are lacking. Areas where these birds are cur- seldom visited, and information on histori- rently nesting are under increasing threats. cal or current populations is lacking. How- Our ability to adequately determine con- ever, unlike many other tropical seabirds, servation needs and management strate- tropicbirds are not confined to remote is- gies is hampered by the general lack of lands and many major islands still support studies on these species. Because breeding viable colonies. Long-term banding studies sites are often in remote and inaccessible would provide valuable information on the areas, many are seldom visited. In many age structure of populations, loyalty to areas data on former abundance are un- colonies and specific nest sites, age at first available and there is little standardization breeding, survival, longevity, and other im- in colony estimates. This is further compli- portant information needed to construct cated by the large number of countries in- population viability models. Genetic stud- volved and the lack of a central seabird da- ies would provide information about the tabase. degree of isolation between nesting colo- Current population numbers for P. l. nies. catesbyi, the race of the White-tailed Trop- The scattered distribution of nesting icbird in the western North Atlantic, range colonies buffers problems that could other- from 4546 to 5276 breeding pairs, a signifi- wise affect the entire populations of these cant decrease from the 1984 estimate of two species. However, it is hard to get re- more than 10,000 pairs. Adding to this the source managers to recognize the impor- population estimates for P. l. ascensionis, the tance of colonies containing only a few Atlantic population of White-tailed Tropic- dozen pairs or even fewer birds. From this birds, the global population is estimated at viewpoint it is impossible to protect spe- approximately 20,000 pairs. cific sites from the piecemeal development The global population of Red-billed which is occurring in the West Indies, and Tropicbirds is estimated at fewer than 8000 because of the tourist industry, many pairs; the P a. mesonauta race of the Red- coastal sites and remote cays are targeted billed Tropicbird is estimated at between for development. 4000 and 5000 breeding pairs. The current The use of traps and rat bait in the im- estimate for the population of these birds in mediate vicinity of nesting areas on Cule- the West Indies is around 2200 pairs. In bra (Puerto Rico) yielded very encouraging view of the material presented and re- results. Schaffner (1988) showed a dramatic viewed in this paper, we suggest that the global population of the Red-billed Tropic- decrease in egg and chick predation (30- bird and the Atlantic populations of the 50%) and a corresponding major increase in White-tailed Tropicbird should be re- hatching success ( 30-50%) by controlling garded as rare and declining species of rats around nest sites. high conservation priority. In Bermuda, the use of artificial nest burrows has been attempted in the sides of Acknowledgments.—We thank the mem- quarry walls and retaining walls. Several bers of the Seabird Working Group of the such sites were occupied within a year. On Society of Caribbean Ornithology for their islands in the Pacific Ocean, the simple information on breeding colonies in their stacking of rocks in ways that provided respective islands: Kevel Lindsay (Antigua, shaded nesting shelters created dens that Barbuda, and Redondo), David Wingate were occupied by tropicbirds within hours (Bermuda), P. A. Buckley (Barbados), Patri- (Lee and Walsh-McGehee, 1998). cia Bradley (Cayman Islands), Nicasio Vin˜a 278 D. S. LEE AND M. WALSH-MCGEHEE

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