Brown booby

Voice

Silent at sea. At the colony the female gives harsh, grating quacks and honks while the male produces a high, sibilant whistle: a waaah against a thin fweeee. The difference between the sexes is so marked that sound alone tells you which bird is on the nest.

Identification

Smaller and slimmer than a Northern Gannet, 64 to 85 centimetres, with narrower wings and a pointed tail often spread like a fan. The adult is evenly dark chocolate brown on head, neck, upperparts and upper breast, all of it cut off knife-sharp against the white lower breast and belly. The underwing is white with a broad dark border along the leading and trailing edges, a pattern that still reads against the light. The bill is pale horn to pale yellow, yellower on the female, with bluish facial skin on the male; legs and feet are pale yellow. Juveniles are dull brown throughout, the belly at most a shade paler than the breast, with a pale panel down the middle of the underwing. It plunges at a far shallower angle and from far lower than a Gannet, often right along the surf, and flies low over the water with fast beats between short glides.

Confusion species

The main confusion is a juvenile Northern Gannet. That bird is larger and heavier, slate-grey to blackish brown with fine white spotting all over, and has no sharp border between dark breast and white belly: the underparts pale gradually and unevenly. Its bill is dark grey rather than pale, its head longer and heavier, and it dives almost vertically from tens of metres, where the Brown Booby enters low and at an angle. In the Red Sea the much whiter Masked Booby, with its black trailing edge and black tail, is no problem, but its juveniles show a white hind collar that Brown Booby lacks; Red-footed Booby is smaller, with red feet and a blue bill base. A distant dark shearwater lacks the dagger bill and the white belly panel.

Habitat

Warm coastal seas and shelf waters, usually within sight of land. It rests and breeds on rocky islets, cliffs and bare coral shores, and en route it readily perches on buoys, beacons and ships' masts. It fishes closer inshore than the other sulids, including in the surf and over shallow reefs.

Range and movements

Pantropical in all warm seas. Within the area of this guide the Red Sea is the stronghold: from the islands at the mouth of the Gulf of Suez southwards it breeds along the Egyptian and Saudi coasts, with something like eighty pairs in Egypt and far larger numbers further south. In the eastern Atlantic the nearest colonies are in Cape Verde, some thousand pairs on Raso, Boavista, Santiago, Brava and the Rombos islets; from there birds occasionally reach the Canaries, Madeira and the Azores, where the species remains a vagrant. Further north records are increasing: Britain had its first in 2019 and the Netherlands has three accepted records, from 2017 and twice in 2020.

• Winter
• Passage
• dark = core range, pale = thinly spread

Where and when to look

For a certain sighting go to the Egyptian Red Sea: a boat trip from Hurghada or Marsa Alam out to the reef islets produces birds all year, and around midday they sit thickest on beacons and buoys. To try for one in Europe, seawatch in the Canaries — from Punta de la Rasca or Punta de Teno on Tenerife, or from the deck of the La Gomera ferry — preferably between August and November and in the first hours after sunrise, when the sea is flat and birds fish close along the coast.

Conservation status

Not globally threatened (IUCN: Least Concern), with a large and widespread world population. Regionally the picture is less settled: in Macaronesia the Cape Verde population is markedly smaller than it was in the early twentieth century, and in the Red Sea the taking of eggs and chicks, disturbance by day-trip boats and the building of tourist infrastructure press on the colonies. Introduced rats and cats on breeding islands and longline bycatch are the other recurring problems.