Records of brown booby Sula leucogaster in the Pitcairn Islands with additional observations during 2015–19

The Pitcairn Islands are a UK Overseas Territory comprising four islands (Oeno, Pitcairn, Henderson and Ducie) spanning >600 km in eastern Polynesia, in the South Pacific Ocean. Oeno and Ducie are low coral atolls, Henderson is a large raised coral island, and Pitcairn is volcanic in origin (Spencer 1995).

The islands' avifauna have received considerable scientific attention, mainly focused on Henderson Island, beginning in the early 20th century (North 1908, Ogilvie-Grant 1913), followed by the Whitney South Seas Expedition (Murphy 1924, Murphy & Mathews 1929). There was some work in the late 1980s on Henderson's landbirds (Graves 1992). The Sir Peter Scott Memorial Expedition in 1991–92 stationed researchers on Henderson Island for more than a year, and thoroughly studied the birds (Brooke 1995a,b, Brooke & Jones 1995, Imber et al. 1995, Jones et al. 1995, Trevelyan 1995). This was followed in the early 21st century by studies into the effect of introduced Pacific Rats Rattus exulans on Henderson's native fauna (Brooke et al. 2011, Amos et al. 2016, Oppel et al. 2016, Bond et al. 2019b), and of the abundance of various species (Oppel et al. 2017, Bond et al. 2019a). There are far fewer studies of the avifauna of Pitcairn (Williams 1960, Schofield & Bond 2016), Oeno (Brooke et al. 2018) and Ducie, although all were reviewed by Brooke (1995b) and Bourne & David (1983).

Ducie and Oeno possess no endemic species of birds, whilst Pitcairn is home to the endemic Pitcairn Reed Warbler Acrocephalus vaughani (Brooke 1995b), and Henderson supports five endemic species—Henderson Petrel Pterodroma atrata, Henderson Crake Zapornia atra, Henderson Fruit Dove Ptilinopus insularis, Henderson Lorikeet Vini stepheni and Henderson Reed Warbler Acrocephalus taiti (Graves 1992, Brooke 1995b, Oppel et al. 2017, Bond et al. 2019a). The avifauna of the group as a whole has been described largely in three works (Williams 1960, Brooke 1995b, Thibault & Cibois 2017), and one review (Bourne & David 1983).

Of the 41 species recorded from the islands (