Birdfinding.info ⇒ Locally common on its breeding grounds, but otherwise rarely encountered. In the U.S., it is most often seen on summer pelagic trips out of Hatteras, North Carolina. During the breeding season (January to June), it can be seen from shore at various points in Bermuda, the Bahamas, Turks & Caicos, Cayman Brac, and the Greater Antilles: in the D.R., the Santo Domingo aquarium and Cabo Rojo; on Puerto Rico, Quebradillas, Cabo Rojo National Wildlife Refuge, and occasionally Old San Juan; and on Jamaica, Negril and Hector’s River. Breeding adults tend to be most visible near their nest sites from late January into March, with early morning and late afternoon being the best times to look. Depending on nesting success, they remain attached to these sites into May or June.
Catesby’s Tropicbird
Phaethon catesbyi
Breeds in Bermuda and the West Indies and disperses across offshore waters of the Caribbean and western North Atlantic.
Breeding. Breeds from January to June on islets and cliffs of Bermuda, the Bahamas, Cuba, the Cayman Islands, Jamaica, Hispaniola, Puerto Rico, and sparingly through the Virgin Islands and Lesser Antilles south to Tobago.
The largest known breeding colonies are on Bermuda, Mona Island, Providenciales, Cayman Brac, and the southern tip of the Dominican Republic.
A 2009 estimate of the total breeding population was between 3,341 and 5,298 pairs at 203 known nesting locations (Lee and Mackin 2009).
A tiny outpost population breeds on the Abrolhos Islands of southeastern Brazil.
Nonbreeding. Exclusively pelagic away from its breeding grounds, and uncommon even in the presumed core of its range: the Caribbean and Sargasso Seas and adjacent Gulf Stream waters. Has also been found occasionally in the Gulf of Mexico and east of the Lesser Antilles, and very rarely far out at sea in the North Atlantic east to the Azores.
Also recorded from a few points along the eastern coast of Brazil—likely individuals dispersing from the Abrolhos Islands, but possibly also including new immigrants from the North Atlantic. E.g., at Salvador, Bahia, on March 30, 2018, captured in a smartphone video by Eduardo Teixeira Filho.
Identification
Adult is white with two conspicuous black bars on the upperside of each wing. The bill is usually orange, but varies from yellow to reddish.
Catesby’s Tropicbird. (Spittal Pond Nature Reserve, Bermuda; August 7, 2019.) © Richard Caslon
Catesby’s Tropicbird, showing typically orange bill and small amounts of white in the tips of its outer primaries. (Spittal Pond Nature Reserve, Bermuda; March 3, 2019.) © Tim White
Catesby’s Tropicbird, with bill appearing orange. (Santo Domingo, Dominican Republic; March 20, 2015.) © Jason Leifester
Catesby’s Tropicbird, with bills appearing orange. (Hector’s River, Jamaica; April 13, 2014.) © Gil Ewing
Catesby’s Tropicbird, with bills appearing yellow. (Santo Domingo, Dominican Republic; March 20, 2015.) © Jason Leifester
Catesby’s Tropicbird. (Offshore south of Nantucket, Massachusetts; August 23, 2015.) © Jeffrey Offermann
Catesby’s Tropicbird, showing typically orange bill of breeding adult. (Offshore from Cape Canaveral, Florida; June 2, 2019.) © Steve Raduns
Catesby’s Tropicbird, with bill appearing orange. (Nonsuch Island, Bermuda; April 6, 2017.) © Andrew Dobson
Catesby’s Tropicbird. (Abrolhos Islands, Brazil; August 27, 2016.) © Fernando Farias
Catesby’s Tropicbird. (Layou, Dominica; March 28, 2018.) © Colin D. Jones
Catesby’s Tropicbird. (Abrolhos Islands, Brazil; February 29, 2016.) © Ademir Carletti
Catesby’s Tropicbird, with a yellowish tail. (Bitter Guana Cay, Bahamas; March 25, 2019.) © Kamella Boullé
In flight, the adult’s bold black primary and carpal bars are usually diagnostic. Sometimes this dorsal pattern can be seen through the wings from below.
Catesby’s Tropicbird, ventral view with dorsal pattern showing through. (Offshore from Martinique; March 2, 2018.) © Brian Sullivan
Catesby’s Tropicbird. (Offshore from Cape Hatteras, North Carolina; May 30, 2011.) © Steve Calver
Catesby’s Tropicbird. (Offshore from Cape Canaveral, Florida; June 2, 2019.) © Steve Raduns
Catesby’s Tropicbird. (Offshore from Cape Canaveral, Florida; June 3, 2017.) © Michael Rasi
At rest, with wings folded, adult’s back can appear almost solid black.
Catesby’s Tropicbird. (Nonsuch Island, Bermuda; April 3, 2018.) © Andrew Dobson
Catesby’s Tropicbird, on nest. (Abrolhos Islands, Brazil; February 2, 2013.) © Robson Czaban
Catesby’s Tropicbird, on nest. (Nonsuch Island, Bermuda; April 3, 2018.) © Andrew Dobson
Catesby’s Tropicbirds at nest. (Cayo San Luis, Culebra, Puerto Rico; February 6, 2017.) © Jenn Megyes
Immature Plumages. Juvenile’s head can appear either mostly white with a slight “eye-shadow” effect, or gray with a distinct eyeline. Its bill is usually bicolored—pale with a dark tip—but can also be all-pale or mostly dark.
The amount of black in the juvenile’s wings also varies. The folded wings may appear mostly white or mostly black.
Catesby’s Tropicbird, juvenile. (Nonsuch Island, Bermuda; November 21, 2016.) © Tom Johnson
Catesby’s Tropicbird, juvenile, dorsal view of barring pattern on upperparts. (Grand Lucayan Resort, Grand Bahama; August 24, 2013.) © Erika Gates
Catesby’s Tropicbird, juvenile with heavily marked upperparts. (Ferry Point Park, Bermuda; October 6, 2017.) © Paul Watson
Catesby’s Tropicbird, juvenile with lightly marked upperparts. (Burt Island, Bermuda; October 22, 2017.) © Richard Brewer
Catesby’s Tropicbird, juvenile. (Bear Island, Hammocks Beach State Park, North Carolina; August 12, 2020.) © Jacob Vitak
Cf. Red-billed Tropicbird. Catesby’s and Red-billed Tropicbirds occur together across much of the Caribbean region and western North Atlantic. Viewed from below, they can be difficult to distinguish, even at close range in good light. Both have white tails and can have orange bills—though an adult with a bill that appears pale orange or yellow is likely Catesby’s, whereas a dark orange or red bill indicates Red-billed. They are best distinguished by dorsal pattern:
Adult Catesby’s has two thick black bars on each wing—one on its outer primaries (not including the coverts) and the other a diagonal carpal bar across its secondary coverts.
Catesby’s Tropicbird. (Spittal Pond Nature Reserve, Bermuda; August 7, 2019.) © Richard Caslon
Red-billed Tropicbird. (Gardner Bay, Española, Galápagos, Ecuador; November 4, 2016.) © Neil Wingert
Adult Red-billed typically has a single, longer black bar on the leading edge of the primaries, tapering inward on primary coverts, creating a sharp white “comma” at the wrist, and lacks the solid black carpal bar of Catesby’s. Some Red-billed have more heavily marked upperparts than average and may appear to have a carpal bar like Catesby’s, but on these individuals the rest of the back is also heavily marked, unlike Catesby’s.
Immatures of the two species can be very difficult to distinguish at sea, as both can have yellow bills, black primaries, and black barring across the back, rump, and wing coverts. The most reliable distinction is the head markings: Catesby’s has a short, smudgy eyeline, whereas Red-billed usually has a complete “headband,” as its eyelines extend back and join to form a collar on the nape.
Catesby’s Tropicbird, juvenile. (Nonsuch Island, Bermuda; November 21, 2016.) © Tom Johnson
Red-billed Tropicbird, immature. (Offshore from Santa Cruz Huatulco, Oaxaca, Mexico; March 31, 2017.) © Mark L. Hoffman
Immature Catesby’s has whiter upperparts, particularly on the head and neck, and the black bar on its outer wing is limited to the primaries, covering the outer 25-30% of the wing and ending squarely—whereas on Red-billed the black bar extends onto the primary coverts, tapering toward the wrist, and spans almost 50% of the outstretched wing.
Cf. Yellow-billed Tropicbird. The tropical Atlantic is home to both Catesby’s and Yellow-billed Tropicbirds. Their ranges overlap widely in Brazilian waters, and both have been recorded from Macaronesia (Catesby’s at least somewhat regularly in the Azores and Yellow-billed twice in Cape Verde). They are extremely similar and can be effectively indistinguishable unless seen well at close range or photographed.
Catesby’s is slightly larger than Yellow-billed, though this would require a close comparison to evaluate. The two differences that are often objective and detectable are bill color and the amounts of black and white on the uppersides of the wingtips.
Bill Color: Catesby’s bill tends to appear more orange than yellow, especially in breeding adults, whereas most Yellow-billed are pale-yellow, often greenish or horn-colored. However, a few Yellow-billed show orange bills (perhaps only briefly, early in the breeding season) and Catesby’s’ bill frequently appear yellow (perhaps mostly on youngish individuals), so there is significant overlap in this feature. For individuals at either end of the spectrum, it is effectively diagnostic, but for those in the middle it is ambiguous.
Yellow-billed Tropicbird, P. l. ascensionis, thousands of miles north of its usual range—note pale greenish-yellow bill and white in wingtips. (Offshore west of Praia, Santiago, Ilhas de Sotavento, Cape Verde; May 3, 2011.) © Angus Wilson
Catesby’s Tropicbird—note orange bill and mostly black wingtips with only small white spots. (Offshore from Cape Hatteras, North Carolina; May 30, 2011.) © Steve Calver
Wingtip Pattern: Probably the most reliable distinction is the pattern of black in the outer primaries. However, this difference is subtle and Yellow-billed appears to vary more internally than it differs from Catesby’s. Both species have extensive black on the outer primaries—generally more on Catesby’s, but they both vary. The objective difference is the amount of white in the tips of the four outermost primaries: an appreciable amount of white on Yellow-billed versus almost none on Catesby’s.
This difference seems to be consistent but it can be confusing because there are borderline cases on both sides of the line: i.e., some Yellow-billed have very little white at the tips of one or two primaries, and some Catesby’s have appreciable white at the tips of one or two primaries, but the two do not quite overlap.
The wingtip distinction can be difficult to interpret in part because on both species the black is usually limited to the outer web of each feather. The inner webs of all the primaries are entirely white, so any feather could potentially appear to have an extensively white tip, depending on how it is exposed. Overall, this feature is useful in most cases (at least for photos and specimens), but hard to apply accurately in some cases.
Notes
Monotypic species. Traditionally classified as a subspecies of White-tailed Tropicbird, but Howell and Zufelt (2019) recognize it as a separate species, and the evidence in favor of this change is compelling—for a detailed analysis, see Frontiers of Taxonomy: Split the Tropics!
Catesby’s Tropicbird Breeds in Brazil. It has long been known that Brazil has two breeding populations of White-tailed Tropicbird: a large population in the northeast on Fernando de Noronha and a few pairs in the southeast on the Abrolhos Islands. As ornithological reference works define each subspecies primarily by the geography it is thought to occupy, these populations have been presumed to pertain to the South Atlantic subspecies ascensionis.
When reviewing 257 photos tagged as Phaethon lepturus on the excellent Brazilian bird website Wikiaves, I noticed that all of the photos from the Abrolhos and coastal Bahia have wingtips consistent with catesbyi, but not ascensionis. Of the photos from Fernando de Noronha, 99% of the identifiable individuals have ascensionis’s wingtips, whereas one individual is clearly catesbyi. (In addition, several of the photos lack sufficient details for identification to species and several others are either clearly or probably Red-billed Tropicbirds misidentified by the photographers.)
While far from comprehensive, the results of this review seem conclusive: the tiny Abrolhos population is of catesbyi, which also wanders occasionally to the mainland coast and the Fernando de Noronha, where ascensionis breeds in numbers. This discovery is of particular interest because it shows that catesbyi and ascensionis have effectively overlapping (or at least adjacent and interpenetrating) breeding ranges, but they do not appear to interbreed—or if they do hybridize at either location, it is not readily detectable at the population level.
The existence of a population of catesbyi in southeastern Brazil appears to confirm its status as a species separate from the rest of the White-tailed Tropicbird complex, as proposed in Howell and Zufelt’s 2019 book Oceanic Birds of the World.
References
eBird. 2020. eBird: An online database of bird distribution and abundance. Cornell Lab of Ornithology, Ithaca, N.Y. http://www.ebird.org. (Accessed August 31, 2020.)
Garcia-del-Rey, E. 2011. Field Guide to the Birds of Macaronesia: Azores, Madeira, Canary Islands, Cape Verde. Lynx Editions, Barcelona.
Harrison, P. 1983. Seabirds: An Identification Guide. Houghton Mifflin, Boston.
Howell, S.N.G., and K. Zufelt. 2019. Oceanic Birds of the World. Princeton University Press.
Latta, S., C. Rimmer, A. Keith, J. Wiley, H. Raffaele, K. McFarland, and E. Fernandez. 2006. Birds of the Dominican Republic and Haiti. Princeton University Press, Princeton, N.J.
Le Corre, M. and P. Jouventin. 1999. Geographical variation in the White‐tailed Tropicbird Phaethon lepturus, with the description of a new subspecies endemic to Europa Island, southern Mozambique Channel. Ibis 141(2):233-239.
Lee, D.S. and W.A. Mackin. 2009. White‐tailed Tropicbird. West Indian Breeding Seabird Atlas. http://www.wicbirds.net/wttr.html. (Accessed October 20, 2018.)
Raffaele, H., J. Wiley, O. Garrido, A. Keith, and J. Raffaele. 1998. A Guide to the Birds of the West Indies. Princeton University Press, Princeton, N.J.
Wikiaves. 2020. Rabo-de-palha-de-bico-laranja, https://www.wikiaves.com.br/wiki/rabo-de-palha-de-bico-laranja. (Accessed September 1, 2020.)