Abbott's Booby Papasula abbotti Scientific name definitions

79 cm; male 1370–1620 g, female 1470–1700 g. A typical booby with large eye and large and coarsely serrated bill; in flight looks very slim, with long and noticeably narrow wings, neck narrower than head. Adult has head and neck white, nape feathers elongated, often giving it a shaggy appearance, rest of upperparts white blotched or spotted with black on rump and uppertail-coverts, most of scapulars and upperwing black, the latter with feathers partially white on inner webs, often showing through here and there, marginal feathers white most noticeable at wing-base and at carpal joint; tail black with white base of outermost pair of rectrices; underwing  white with broad black tips of primaries , dark tips becoming partial and much smaller or vestigial on secondaries and tertials, may show a thin but noticeable white fringe on trailing edge at base of wing; underparts white except for irregular black patch from rear thigh through rear flanks; black feathers bleaching into dull dark brown in worn plumage, the white areas may have some dull apricot staining; iris  blackish brown; blackish facial skin on lores and around eye giving it a large-eyed looking, paler greyish on anterior eyelids; bill dull bluish grey often slighly tinged with pink, bluer at base (thinly bordered with blackish at base next to forehead), contrasting black tip; legs grey or bluish grey, distal third of webs duskier grey to blackish, claws horn colour  . Sexes alike except that the female has pink instead of grey on bill  , becoming duller during breeding. Juvenile very like adult male, iris dusky (less balckish than adult’s). Confusion with other boobies and gannets unlikely, especially in flight; some morphs of S. sula superficially similar in overall pattern, but present species lacks dark carpal patch on underwing and differs in upperpart colours and general structure.

Breeding confined to Christmas I, in E Indian Ocean; dispersal and foraging over long distances, but very little information available and at-sea distribution poorly known. Formerly bred on several islands in W Indian Ocean; fossil remains found in Solomon Is, W Pacific; a female at Rota (Northern Mariana Is) in mid-Apr 2007 represents the first documented record of this species in WC Pacific Ocean (1 Pratt, H.D., Retter, M.L.P., Chapman, D., Ord, W.M. and Pisano, P. (2009). An Abbott’s Booby Papasula abbotti on Rota, Mariana Islands: first historical record for the Pacific Ocean. Bull. Brit. Orn. Club 129(2): 87–91. Close ); recorded also in Banda Sea and Chagos Archipelago.

Strictly marine and pelagic. Breeds in the rainforest canopy on the central C plateau of Christmas I  , at c. 160–260 m.

Very poorly known. Adults probably largely sedentary, given exceptionally long breeding cycle, but often perform lengthy foraging flights; immatures and non-breeders largely absent from Christmas I. Disperses mainly within Indian Ocean, with recent record (Oct 2014) at the Maldives (2 Anderson, R.C., Bray, N., Thomas, S. and Maher, M. (2016). First records of three seabirds for the Maldives. BirdingASIA 26:129–131. Close ); recorded also in Banda Sea (W Pacific), and a female at Rota , in Northern Mariana Is, in mid-Apr 2007 represents first documented record of this species in WC Pacific Ocean (3 Pratt, H. D., Retter, M. L. P., Chapman, D., Ord, W. M. and Pisano, P. (2009). An Abbott’s Booby Papasula abbotti on Rota, Mariana Islands: first historical record for the Pacific Ocean. Bull. BOC. 129(2): 87-91. Close ).

Poorly known. Feeds on fish, especially flying-fish (Exocoetidae), and squid. Presumably plunge-dives like other members of family. Formerly thought to forage over cold-water upwellings S of Java (4 Dunlop, J.N., Surman, C.A. and Wooler, R.D. (2001). The marine distribution of seabirds from Christmas Island, Indian Ocean. Emu. 101(1): 19–34. Close ), but recent tracking studies seem to indicate that the birds forage anywhere within 40–100 km of Christmas I. Will undertake long foraging trips to favourable feeding zones, and frequently away from nest for several days.

At nest-site gives variety of calls  , including loud “aaw-ah-errr”, also “oya-oya” and “ku-ark ko-ark”; also croaks, groans and other odd sounds.

Fairly seasonal, most laying in May–Jul; breeds biennially or even less frequently, when successful. Fairly solitary, with maximum density of c. 9 pairs/ha. Nest a dishevelled stick platform built in top of tall rainforest tree, often Planchonella or Eugenia. Clutch invariably one egg; incubation period c. 57 days; chick has whitish down; fledging period 140–175 days; post-fledging care 162–280 days. First breeding possibly not until eight years of age, some perhaps at 4–6 years. Average lifespan may be c. 40 years.

ENDANGERED. CITES I. Breeds at a single small island, on which it nests in suitable habitat in just one area; small population has declined rapidly as a result of effects of earlier habitat clearance. According to BirdLife, current global population thought to include c. 6000 mature individuals, equivalent to total of c. 9000 individuals in all. In 1967, adult population was put at 2300 pairs, declining to 1900 pairs by 1983; following survey in 1991 (considered the most accurate and comprehensive to date), newly discovered breeding sites raised total to estimated 2500 active pairs; in 2002 helicopter survey recorded c. 1500 active nest-sites, but results not corroborated by ground-based surveys. General impression that breeding population more or less stable between 1991 and 2002, but survey techniques not directly comparable. Moreover, since only a proportion breed in any given year (as breeding cycle 15–18 months), and possible that some unsuccessful pairs take “rest years” (rather than breeding in successive years), true assessment of population very difficult. Recruitment to the population is very slow since breeding is biennial, only one young bird is raised and juvenile mortality is high. Hence pairs are thought to replace themselves only once every 24 years on average (5 Boland, C.R.J., Smith, M.J., Maple, D., Tiernan, B. and Napier, F. (2012). An island-wide survey of Abbott’s Booby Papasula abbotti occupancy on Christmas Island, Indian Ocean. Marine Orn.. 40(1): 99–103. Close ). Formerly bred on several islands in W Indian Ocean (Assumption, Seychelles, Rodrigues, Mauritius), and fossil remains recently found in W Pacific (Solomon Is), but population believed to have declined by 30–49% since early 20th century following disappearance from much of earlier breeding range in those oceans. Disperses within Indian Ocean; recent records from Banda Sea, in W Pacific, may indicate either an important extension of its known range or existence of unknown breeding colonies; in WC Pacific, a female observed on Rota I (Northern Mariana Is), E of Philippines, in Apr 2007, though not known whether a vagrant or a solitary resident (3 Pratt, H. D., Retter, M. L. P., Chapman, D., Ord, W. M. and Pisano, P. (2009). An Abbott’s Booby Papasula abbotti on Rota, Mariana Islands: first historical record for the Pacific Ocean. Bull. BOC. 129(2): 87-91. Close ). Main problem appears to have been loss of suitable breeding habitat. From mid 1960s until 1987 more than 30% of habitat was lost through phosphate-extraction activities, in addition to which various exotic plants which have colonized (and been introduced) at old mine sites sometimes invade surviving forest and threaten habitat recovery. Further habitat loss can result from clearance for mining works, e.g. significant patches of mature secondary forest were cleared for mining in 2007; in latter year a new application to mine an area of 250 ha of rainforest was rejected, but subsequently went to appeal. Most serious current threat perhaps the introduced yellow crazy ant (Anoplolepis gracilipes), which formed super-colonies during 1990s and rapidly spread to cover almost 30% of forest on the island (6 O’Dowd, D.J., Green, P.T. and Lake, P.S. (2003). Invasional ‘meltdown’ on an oceanic island. Ecol. Lett. 6: 812–817. Close ); despite reasonably successful efforts to control the ants, which at beginning of 2005 were estimated to be present on 300 ha of the island, with densities considerably lower than prior to control, in 2006 the ants were regarded as widespread and patchily common; the yellow crazy ant occurs from below ground-level up to canopy (where this booby  nests) and, if allowed to spread freely, ant super-colonies may prey directly on booby nestlings or cause abandonment of nests, although there is no evidence of such events so far (7 Donald, P.F., Collar, N.J., Marsden, S.J. and Pain, D.J. (2010). Facing Extinction. T. & A.D. Poyser, London. Close ). Super-colonies of ants modify the island’s ecology by killing the dominant life form, the red crab (Gecaroidea natalis), and by farming scale insects (Coccoidea), which damage trees; forest die-back in a small area of breeding habitat may be indirectly caused or exacerbated by this ant, but its impact seems unlikely to be severe. Otherwise, breeding boobies are susceptible to extreme weather events, as e.g. in 1988, when a cyclone destroyed a third of monitored fledglings and nest-sites; in severely wind-affected areas, increased turbulence can cause higher adult mortality and reduce fledging success, and clearance of forest, e.g. for roads and buildings, also leads to increased wind turbulence. Other threats affecting this and other seabird species include overfishing and marine pollution; climate change may be a further threat through changes in sea-surface temperatures, rainfall patterns and El Niño Southern Oscillation (although this species unlikely to be affected by sea-level rise, as it nests above 100 m). May suffer from direct hunting and bycatch, but this not hitherto documented. A national park, first created in 1980, has since been extended to cover more than 60% of Christmas I, and this includes most of this booby’s breeding areas. However, a recent survey has found that although it now inhabits previously unoccupied areas it has not re-occupied habitat adjacent to areas that were cleared for phosphate mining several decades ago (5 Boland, C.R.J., Smith, M.J., Maple, D., Tiernan, B. and Napier, F. (2012). An island-wide survey of Abbott’s Booby Papasula abbotti occupancy on Christmas Island, Indian Ocean. Marine Orn.. 40(1): 99–103. Close ).