Family Gannets, Boobies (Sulidae)

Least Concern

Red-footed Booby (Sula sula)

You are currently reading a free species account of the HBW Alive. To make the most of all of HBW's features, discover our subscriptions now!
HBW Alive Plans & Pricing  Why subscribe

Taxonomy

French: Fou à pieds rouges German: Rotfußtölpel Spanish: Piquero patirrojo
Taxonomy:

Pelecanus Sula

Linnaeus

, 1766,

Barbados, West Indies

.

Validity of races often questioned, and delimitation difficult owing to existence of colour morphs. On other hand, has been suggested that websteri may be a separate species#R#R. Three subspecies commonly recognized.

Subspecies and Distribution
  • S. s. sula (Linnaeus, 1766) – islands in Caribbean and off E Brazil (Fernando de Noronha, Trindade), and Ascension I (S Atlantic).
  • S. s. rubripes Gould, 1838 – islands in Indian Ocean and tropical W & C Pacific Ocean E to Hawaiian Is, Line Is, Marquesas and Pitcairn Is.
  • S. s. websteri Rothschild, 1898 – tropical E Pacific Ocean from Revillagigedo Is (off SW Mexico) S to Galapagos.
  • Descriptive notes

    66–77 cm; 900–1003 g; wingspan 124–152 cm#R. Smallest booby, with relatively long tail and large eye; highly polymorphic, with variety of morphs (and intermediates) irrespective of subspecies. Adult white morph has all-white plumage, often more or less tinged apricot-yellow, except mostly black primaries (pale basally), secondaries and greater upperwing-coverts and primary-coverts, the outer webs often with noticeable silver-grey cast; underwing has chracteristic blackish-grey carpal patch formed by some outer or most median primary-coverts; some white-morph birds have blackish tail, others have white tail but entirely dark upperwing and ‘saddle’; brown morph has entire plumage highly variable from tan to chocolate-brown, darkest birds having tail, remiges and primary-coverts just slightly darker than rest of upperparts, but many are palest on head, neck and underparts, and darkest on wing and tail, some have white on rear body and tail; iris blackish brown, often with paler narrow outer ring; at its brightest, bill is pale greyish blue, duller at tip, cutting edges tinged green-yellow, band of naked red skin at junction of culmen and forehead, and patch of similar red skin at base of mandible bordered behind and below by narrow black line of naked skin running from gape to gular pouch, bare skin around eye and on lores bright blue to turquoise with deeper blue to blackish spot just before eye, and lime-green to bluish-green patch below eye that fades at start of breeding; all bare facial skin is less bright when not in courtship, the red becoming duller and paler pink, and bill lacks greenish-yellow tinge; legs red to bright reddish orange. Sexes alike in plumage, but female averages larger and bare facial skin lacks lime-green colour during courtship. Juvenile entirely earth brown to dark brown, often paler on foreneck and abdomen (especially rear), leaving diffuse narrow pectoral band, underwing variable (coverts vary from pale brown to blackish brown) but not strongly patterned, iris grey or dark brown to yellowish, bill blackish, facial skin dark slate, paler on gular pouch, legs dark grey to dull orange-flesh. Subsequent immature varies according to morph, but even in brown morph  plumage less uniform, more blotchy, with pale tips giving brown plumage spotted look, pinkish bill with blackish tip, facial skin blue-grey, legs dull yellowish orange to reddish pink. Subspecies fairly similar, websteri slightly smaller, rubripes slightly larger than nominate. Bare-part colours of adults unique among sulids; at some distance white-tailed morph could be confused with larger S. dactylatra or any of the three gannets, but readily separated from all of these (except adult Morus bassanus) by all-white tail, and M. bassanus is larger and has white not black secondaries, while dark carpal on underwing of S. sula is also useful; brown birds could be confused with juvenile gannets, but have uniform upperparts (no white horseshoe on uppertail-coverts) and lacking strongly contrasting underparts and underwing; immature of present species in ventral view may resemble immature gannet, but is smaller overall, with usually thinner bill and different-coloured feet; relatively large dark eye and bill colour of second-plumaged immatures may recall otherwise highly characteristic Papasula abbotti.

    Adult white morph
    Drawing by Francesc Jutglar
    Adult white morph
    Descriptive notes:

    66–77 cm; 900–1003 g; wingspan 124–152 cm#R. Smallest booby, with relatively long tail and large eye; highly polymorphic, with variety of morphs (and intermediates) irrespective of subspecies. Adult white morph has all-white plumage, often more or less tinged apricot-yellow, except mostly black primaries (pale basally), secondaries and greater upperwing-coverts and primary-coverts, the outer webs often with noticeable silver-grey cast; underwing has chracteristic blackish-grey carpal patch formed by some outer or most median primary-coverts; some white-morph birds have blackish tail, others have white tail but entirely dark upperwing and ‘saddle’; brown morph has entire plumage highly variable from tan to chocolate-brown, darkest birds having tail, remiges and primary-coverts just slightly darker than rest of upperparts, but many are palest on head, neck and underparts, and darkest on wing and tail, some have white on rear body and tail; iris blackish brown, often with paler narrow outer ring; at its brightest, bill is pale greyish blue, duller at tip, cutting edges tinged green-yellow, band of naked red skin at junction of culmen and forehead, and patch of similar red skin at base of mandible bordered behind and below by narrow black line of naked skin running from gape to gular pouch, bare skin around eye and on lores bright blue to turquoise with deeper blue to blackish spot just before eye, and lime-green to bluish-green patch below eye that fades at start of breeding; all bare facial skin is less bright when not in courtship, the red becoming duller and paler pink, and bill lacks greenish-yellow tinge; legs red to bright reddish orange. Sexes alike in plumage, but female averages larger and bare facial skin lacks lime-green colour during courtship. Juvenile entirely earth brown to dark brown, often paler on foreneck and abdomen (especially rear), leaving diffuse narrow pectoral band, underwing variable (coverts vary from pale brown to blackish brown) but not strongly patterned, iris grey or dark brown to yellowish, bill blackish, facial skin dark slate, paler on gular pouch, legs dark grey to dull orange-flesh. Subsequent immature varies according to morph, but even in brown morph  plumage less uniform, more blotchy, with pale tips giving brown plumage spotted look, pinkish bill with blackish tip, facial skin blue-grey, legs dull yellowish orange to reddish pink. Subspecies fairly similar, websteri slightly smaller, rubripes slightly larger than nominate. Bare-part colours of adults unique among sulids; at some distance white-tailed morph could be confused with larger S. dactylatra or any of the three gannets, but readily separated from all of these (except adult Morus bassanus) by all-white tail, and M. bassanus is larger and has white not black secondaries, while dark carpal on underwing of S. sula is also useful; brown birds could be confused with juvenile gannets, but have uniform upperparts (no white horseshoe on uppertail-coverts) and lacking strongly contrasting underparts and underwing; immature of present species in ventral view may resemble immature gannet, but is smaller overall, with usually thinner bill and different-coloured feet; relatively large dark eye and bill colour of second-plumaged immatures may recall otherwise highly characteristic Papasula abbotti.

    Adult white morph
    Drawing by Francesc Jutglar
    Adult white morph
    Descriptive notes:

    66–77 cm; 900–1003 g; wingspan 124–152 cm#R. Smallest booby, with relatively long tail and large eye; highly polymorphic, with variety of morphs (and intermediates) irrespective of subspecies. Adult white morph has all-white plumage, often more or less tinged apricot-yellow, except mostly black primaries (pale basally), secondaries and greater upperwing-coverts and primary-coverts, the outer webs often with noticeable silver-grey cast; underwing has chracteristic blackish-grey carpal patch formed by some outer or most median primary-coverts; some white-morph birds have blackish tail, others have white tail but entirely dark upperwing and ‘saddle’; brown morph has entire plumage highly variable from tan to chocolate-brown, darkest birds having tail, remiges and primary-coverts just slightly darker than rest of upperparts, but many are palest on head, neck and underparts, and darkest on wing and tail, some have white on rear body and tail; iris blackish brown, often with paler narrow outer ring; at its brightest, bill is pale greyish blue, duller at tip, cutting edges tinged green-yellow, band of naked red skin at junction of culmen and forehead, and patch of similar red skin at base of mandible bordered behind and below by narrow black line of naked skin running from gape to gular pouch, bare skin around eye and on lores bright blue to turquoise with deeper blue to blackish spot just before eye, and lime-green to bluish-green patch below eye that fades at start of breeding; all bare facial skin is less bright when not in courtship, the red becoming duller and paler pink, and bill lacks greenish-yellow tinge; legs red to bright reddish orange. Sexes alike in plumage, but female averages larger and bare facial skin lacks lime-green colour during courtship. Juvenile entirely earth brown to dark brown, often paler on foreneck and abdomen (especially rear), leaving diffuse narrow pectoral band, underwing variable (coverts vary from pale brown to blackish brown) but not strongly patterned, iris grey or dark brown to yellowish, bill blackish, facial skin dark slate, paler on gular pouch, legs dark grey to dull orange-flesh. Subsequent immature varies according to morph, but even in brown morph  plumage less uniform, more blotchy, with pale tips giving brown plumage spotted look, pinkish bill with blackish tip, facial skin blue-grey, legs dull yellowish orange to reddish pink. Subspecies fairly similar, websteri slightly smaller, rubripes slightly larger than nominate. Bare-part colours of adults unique among sulids; at some distance white-tailed morph could be confused with larger S. dactylatra or any of the three gannets, but readily separated from all of these (except adult Morus bassanus) by all-white tail, and M. bassanus is larger and has white not black secondaries, while dark carpal on underwing of S. sula is also useful; brown birds could be confused with juvenile gannets, but have uniform upperparts (no white horseshoe on uppertail-coverts) and lacking strongly contrasting underparts and underwing; immature of present species in ventral view may resemble immature gannet, but is smaller overall, with usually thinner bill and different-coloured feet; relatively large dark eye and bill colour of second-plumaged immatures may recall otherwise highly characteristic Papasula abbotti.

    Adult black-tailed white morph
    Drawing by Francesc Jutglar
    Adult black-tailed white morph
    Descriptive notes:

    66–77 cm; 900–1003 g; wingspan 124–152 cm#R. Smallest booby, with relatively long tail and large eye; highly polymorphic, with variety of morphs (and intermediates) irrespective of subspecies. Adult white morph has all-white plumage, often more or less tinged apricot-yellow, except mostly black primaries (pale basally), secondaries and greater upperwing-coverts and primary-coverts, the outer webs often with noticeable silver-grey cast; underwing has chracteristic blackish-grey carpal patch formed by some outer or most median primary-coverts; some white-morph birds have blackish tail, others have white tail but entirely dark upperwing and ‘saddle’; brown morph has entire plumage highly variable from tan to chocolate-brown, darkest birds having tail, remiges and primary-coverts just slightly darker than rest of upperparts, but many are palest on head, neck and underparts, and darkest on wing and tail, some have white on rear body and tail; iris blackish brown, often with paler narrow outer ring; at its brightest, bill is pale greyish blue, duller at tip, cutting edges tinged green-yellow, band of naked red skin at junction of culmen and forehead, and patch of similar red skin at base of mandible bordered behind and below by narrow black line of naked skin running from gape to gular pouch, bare skin around eye and on lores bright blue to turquoise with deeper blue to blackish spot just before eye, and lime-green to bluish-green patch below eye that fades at start of breeding; all bare facial skin is less bright when not in courtship, the red becoming duller and paler pink, and bill lacks greenish-yellow tinge; legs red to bright reddish orange. Sexes alike in plumage, but female averages larger and bare facial skin lacks lime-green colour during courtship. Juvenile entirely earth brown to dark brown, often paler on foreneck and abdomen (especially rear), leaving diffuse narrow pectoral band, underwing variable (coverts vary from pale brown to blackish brown) but not strongly patterned, iris grey or dark brown to yellowish, bill blackish, facial skin dark slate, paler on gular pouch, legs dark grey to dull orange-flesh. Subsequent immature varies according to morph, but even in brown morph  plumage less uniform, more blotchy, with pale tips giving brown plumage spotted look, pinkish bill with blackish tip, facial skin blue-grey, legs dull yellowish orange to reddish pink. Subspecies fairly similar, websteri slightly smaller, rubripes slightly larger than nominate. Bare-part colours of adults unique among sulids; at some distance white-tailed morph could be confused with larger S. dactylatra or any of the three gannets, but readily separated from all of these (except adult Morus bassanus) by all-white tail, and M. bassanus is larger and has white not black secondaries, while dark carpal on underwing of S. sula is also useful; brown birds could be confused with juvenile gannets, but have uniform upperparts (no white horseshoe on uppertail-coverts) and lacking strongly contrasting underparts and underwing; immature of present species in ventral view may resemble immature gannet, but is smaller overall, with usually thinner bill and different-coloured feet; relatively large dark eye and bill colour of second-plumaged immatures may recall otherwise highly characteristic Papasula abbotti.

    Adult brown morph
    Drawing by Francesc Jutglar
    Adult brown morph
    Descriptive notes:

    66–77 cm; 900–1003 g; wingspan 124–152 cm#R. Smallest booby, with relatively long tail and large eye; highly polymorphic, with variety of morphs (and intermediates) irrespective of subspecies. Adult white morph has all-white plumage, often more or less tinged apricot-yellow, except mostly black primaries (pale basally), secondaries and greater upperwing-coverts and primary-coverts, the outer webs often with noticeable silver-grey cast; underwing has chracteristic blackish-grey carpal patch formed by some outer or most median primary-coverts; some white-morph birds have blackish tail, others have white tail but entirely dark upperwing and ‘saddle’; brown morph has entire plumage highly variable from tan to chocolate-brown, darkest birds having tail, remiges and primary-coverts just slightly darker than rest of upperparts, but many are palest on head, neck and underparts, and darkest on wing and tail, some have white on rear body and tail; iris blackish brown, often with paler narrow outer ring; at its brightest, bill is pale greyish blue, duller at tip, cutting edges tinged green-yellow, band of naked red skin at junction of culmen and forehead, and patch of similar red skin at base of mandible bordered behind and below by narrow black line of naked skin running from gape to gular pouch, bare skin around eye and on lores bright blue to turquoise with deeper blue to blackish spot just before eye, and lime-green to bluish-green patch below eye that fades at start of breeding; all bare facial skin is less bright when not in courtship, the red becoming duller and paler pink, and bill lacks greenish-yellow tinge; legs red to bright reddish orange. Sexes alike in plumage, but female averages larger and bare facial skin lacks lime-green colour during courtship. Juvenile entirely earth brown to dark brown, often paler on foreneck and abdomen (especially rear), leaving diffuse narrow pectoral band, underwing variable (coverts vary from pale brown to blackish brown) but not strongly patterned, iris grey or dark brown to yellowish, bill blackish, facial skin dark slate, paler on gular pouch, legs dark grey to dull orange-flesh. Subsequent immature varies according to morph, but even in brown morph  plumage less uniform, more blotchy, with pale tips giving brown plumage spotted look, pinkish bill with blackish tip, facial skin blue-grey, legs dull yellowish orange to reddish pink. Subspecies fairly similar, websteri slightly smaller, rubripes slightly larger than nominate. Bare-part colours of adults unique among sulids; at some distance white-tailed morph could be confused with larger S. dactylatra or any of the three gannets, but readily separated from all of these (except adult Morus bassanus) by all-white tail, and M. bassanus is larger and has white not black secondaries, while dark carpal on underwing of S. sula is also useful; brown birds could be confused with juvenile gannets, but have uniform upperparts (no white horseshoe on uppertail-coverts) and lacking strongly contrasting underparts and underwing; immature of present species in ventral view may resemble immature gannet, but is smaller overall, with usually thinner bill and different-coloured feet; relatively large dark eye and bill colour of second-plumaged immatures may recall otherwise highly characteristic Papasula abbotti.

    Adult brown morph
    Drawing by Francesc Jutglar
    Adult brown morph
    Descriptive notes:

    66–77 cm; 900–1003 g; wingspan 124–152 cm#R. Smallest booby, with relatively long tail and large eye; highly polymorphic, with variety of morphs (and intermediates) irrespective of subspecies. Adult white morph has all-white plumage, often more or less tinged apricot-yellow, except mostly black primaries (pale basally), secondaries and greater upperwing-coverts and primary-coverts, the outer webs often with noticeable silver-grey cast; underwing has chracteristic blackish-grey carpal patch formed by some outer or most median primary-coverts; some white-morph birds have blackish tail, others have white tail but entirely dark upperwing and ‘saddle’; brown morph has entire plumage highly variable from tan to chocolate-brown, darkest birds having tail, remiges and primary-coverts just slightly darker than rest of upperparts, but many are palest on head, neck and underparts, and darkest on wing and tail, some have white on rear body and tail; iris blackish brown, often with paler narrow outer ring; at its brightest, bill is pale greyish blue, duller at tip, cutting edges tinged green-yellow, band of naked red skin at junction of culmen and forehead, and patch of similar red skin at base of mandible bordered behind and below by narrow black line of naked skin running from gape to gular pouch, bare skin around eye and on lores bright blue to turquoise with deeper blue to blackish spot just before eye, and lime-green to bluish-green patch below eye that fades at start of breeding; all bare facial skin is less bright when not in courtship, the red becoming duller and paler pink, and bill lacks greenish-yellow tinge; legs red to bright reddish orange. Sexes alike in plumage, but female averages larger and bare facial skin lacks lime-green colour during courtship. Juvenile entirely earth brown to dark brown, often paler on foreneck and abdomen (especially rear), leaving diffuse narrow pectoral band, underwing variable (coverts vary from pale brown to blackish brown) but not strongly patterned, iris grey or dark brown to yellowish, bill blackish, facial skin dark slate, paler on gular pouch, legs dark grey to dull orange-flesh. Subsequent immature varies according to morph, but even in brown morph  plumage less uniform, more blotchy, with pale tips giving brown plumage spotted look, pinkish bill with blackish tip, facial skin blue-grey, legs dull yellowish orange to reddish pink. Subspecies fairly similar, websteri slightly smaller, rubripes slightly larger than nominate. Bare-part colours of adults unique among sulids; at some distance white-tailed morph could be confused with larger S. dactylatra or any of the three gannets, but readily separated from all of these (except adult Morus bassanus) by all-white tail, and M. bassanus is larger and has white not black secondaries, while dark carpal on underwing of S. sula is also useful; brown birds could be confused with juvenile gannets, but have uniform upperparts (no white horseshoe on uppertail-coverts) and lacking strongly contrasting underparts and underwing; immature of present species in ventral view may resemble immature gannet, but is smaller overall, with usually thinner bill and different-coloured feet; relatively large dark eye and bill colour of second-plumaged immatures may recall otherwise highly characteristic Papasula abbotti.

    Adult white-headed and white-tailed brown morph
    Drawing by Francesc Jutglar
    Adult white-headed and white-tailed brown morph
    Descriptive notes:

    66–77 cm; 900–1003 g; wingspan 124–152 cm#R. Smallest booby, with relatively long tail and large eye; highly polymorphic, with variety of morphs (and intermediates) irrespective of subspecies. Adult white morph has all-white plumage, often more or less tinged apricot-yellow, except mostly black primaries (pale basally), secondaries and greater upperwing-coverts and primary-coverts, the outer webs often with noticeable silver-grey cast; underwing has chracteristic blackish-grey carpal patch formed by some outer or most median primary-coverts; some white-morph birds have blackish tail, others have white tail but entirely dark upperwing and ‘saddle’; brown morph has entire plumage highly variable from tan to chocolate-brown, darkest birds having tail, remiges and primary-coverts just slightly darker than rest of upperparts, but many are palest on head, neck and underparts, and darkest on wing and tail, some have white on rear body and tail; iris blackish brown, often with paler narrow outer ring; at its brightest, bill is pale greyish blue, duller at tip, cutting edges tinged green-yellow, band of naked red skin at junction of culmen and forehead, and patch of similar red skin at base of mandible bordered behind and below by narrow black line of naked skin running from gape to gular pouch, bare skin around eye and on lores bright blue to turquoise with deeper blue to blackish spot just before eye, and lime-green to bluish-green patch below eye that fades at start of breeding; all bare facial skin is less bright when not in courtship, the red becoming duller and paler pink, and bill lacks greenish-yellow tinge; legs red to bright reddish orange. Sexes alike in plumage, but female averages larger and bare facial skin lacks lime-green colour during courtship. Juvenile entirely earth brown to dark brown, often paler on foreneck and abdomen (especially rear), leaving diffuse narrow pectoral band, underwing variable (coverts vary from pale brown to blackish brown) but not strongly patterned, iris grey or dark brown to yellowish, bill blackish, facial skin dark slate, paler on gular pouch, legs dark grey to dull orange-flesh. Subsequent immature varies according to morph, but even in brown morph  plumage less uniform, more blotchy, with pale tips giving brown plumage spotted look, pinkish bill with blackish tip, facial skin blue-grey, legs dull yellowish orange to reddish pink. Subspecies fairly similar, websteri slightly smaller, rubripes slightly larger than nominate. Bare-part colours of adults unique among sulids; at some distance white-tailed morph could be confused with larger S. dactylatra or any of the three gannets, but readily separated from all of these (except adult Morus bassanus) by all-white tail, and M. bassanus is larger and has white not black secondaries, while dark carpal on underwing of S. sula is also useful; brown birds could be confused with juvenile gannets, but have uniform upperparts (no white horseshoe on uppertail-coverts) and lacking strongly contrasting underparts and underwing; immature of present species in ventral view may resemble immature gannet, but is smaller overall, with usually thinner bill and different-coloured feet; relatively large dark eye and bill colour of second-plumaged immatures may recall otherwise highly characteristic Papasula abbotti.

    Adult white-tailed brown morph
    Drawing by Francesc Jutglar
    Adult white-tailed brown morph
    Descriptive notes:

    66–77 cm; 900–1003 g; wingspan 124–152 cm#R. Smallest booby, with relatively long tail and large eye; highly polymorphic, with variety of morphs (and intermediates) irrespective of subspecies. Adult white morph has all-white plumage, often more or less tinged apricot-yellow, except mostly black primaries (pale basally), secondaries and greater upperwing-coverts and primary-coverts, the outer webs often with noticeable silver-grey cast; underwing has chracteristic blackish-grey carpal patch formed by some outer or most median primary-coverts; some white-morph birds have blackish tail, others have white tail but entirely dark upperwing and ‘saddle’; brown morph has entire plumage highly variable from tan to chocolate-brown, darkest birds having tail, remiges and primary-coverts just slightly darker than rest of upperparts, but many are palest on head, neck and underparts, and darkest on wing and tail, some have white on rear body and tail; iris blackish brown, often with paler narrow outer ring; at its brightest, bill is pale greyish blue, duller at tip, cutting edges tinged green-yellow, band of naked red skin at junction of culmen and forehead, and patch of similar red skin at base of mandible bordered behind and below by narrow black line of naked skin running from gape to gular pouch, bare skin around eye and on lores bright blue to turquoise with deeper blue to blackish spot just before eye, and lime-green to bluish-green patch below eye that fades at start of breeding; all bare facial skin is less bright when not in courtship, the red becoming duller and paler pink, and bill lacks greenish-yellow tinge; legs red to bright reddish orange. Sexes alike in plumage, but female averages larger and bare facial skin lacks lime-green colour during courtship. Juvenile entirely earth brown to dark brown, often paler on foreneck and abdomen (especially rear), leaving diffuse narrow pectoral band, underwing variable (coverts vary from pale brown to blackish brown) but not strongly patterned, iris grey or dark brown to yellowish, bill blackish, facial skin dark slate, paler on gular pouch, legs dark grey to dull orange-flesh. Subsequent immature varies according to morph, but even in brown morph  plumage less uniform, more blotchy, with pale tips giving brown plumage spotted look, pinkish bill with blackish tip, facial skin blue-grey, legs dull yellowish orange to reddish pink. Subspecies fairly similar, websteri slightly smaller, rubripes slightly larger than nominate. Bare-part colours of adults unique among sulids; at some distance white-tailed morph could be confused with larger S. dactylatra or any of the three gannets, but readily separated from all of these (except adult Morus bassanus) by all-white tail, and M. bassanus is larger and has white not black secondaries, while dark carpal on underwing of S. sula is also useful; brown birds could be confused with juvenile gannets, but have uniform upperparts (no white horseshoe on uppertail-coverts) and lacking strongly contrasting underparts and underwing; immature of present species in ventral view may resemble immature gannet, but is smaller overall, with usually thinner bill and different-coloured feet; relatively large dark eye and bill colour of second-plumaged immatures may recall otherwise highly characteristic Papasula abbotti.

    Juvenile
    Drawing by Juan M. Varela
    Juvenile
    Descriptive notes:

    66–77 cm; 900–1003 g; wingspan 124–152 cm#R. Smallest booby, with relatively long tail and large eye; highly polymorphic, with variety of morphs (and intermediates) irrespective of subspecies. Adult white morph has all-white plumage, often more or less tinged apricot-yellow, except mostly black primaries (pale basally), secondaries and greater upperwing-coverts and primary-coverts, the outer webs often with noticeable silver-grey cast; underwing has chracteristic blackish-grey carpal patch formed by some outer or most median primary-coverts; some white-morph birds have blackish tail, others have white tail but entirely dark upperwing and ‘saddle’; brown morph has entire plumage highly variable from tan to chocolate-brown, darkest birds having tail, remiges and primary-coverts just slightly darker than rest of upperparts, but many are palest on head, neck and underparts, and darkest on wing and tail, some have white on rear body and tail; iris blackish brown, often with paler narrow outer ring; at its brightest, bill is pale greyish blue, duller at tip, cutting edges tinged green-yellow, band of naked red skin at junction of culmen and forehead, and patch of similar red skin at base of mandible bordered behind and below by narrow black line of naked skin running from gape to gular pouch, bare skin around eye and on lores bright blue to turquoise with deeper blue to blackish spot just before eye, and lime-green to bluish-green patch below eye that fades at start of breeding; all bare facial skin is less bright when not in courtship, the red becoming duller and paler pink, and bill lacks greenish-yellow tinge; legs red to bright reddish orange. Sexes alike in plumage, but female averages larger and bare facial skin lacks lime-green colour during courtship. Juvenile entirely earth brown to dark brown, often paler on foreneck and abdomen (especially rear), leaving diffuse narrow pectoral band, underwing variable (coverts vary from pale brown to blackish brown) but not strongly patterned, iris grey or dark brown to yellowish, bill blackish, facial skin dark slate, paler on gular pouch, legs dark grey to dull orange-flesh. Subsequent immature varies according to morph, but even in brown morph  plumage less uniform, more blotchy, with pale tips giving brown plumage spotted look, pinkish bill with blackish tip, facial skin blue-grey, legs dull yellowish orange to reddish pink. Subspecies fairly similar, websteri slightly smaller, rubripes slightly larger than nominate. Bare-part colours of adults unique among sulids; at some distance white-tailed morph could be confused with larger S. dactylatra or any of the three gannets, but readily separated from all of these (except adult Morus bassanus) by all-white tail, and M. bassanus is larger and has white not black secondaries, while dark carpal on underwing of S. sula is also useful; brown birds could be confused with juvenile gannets, but have uniform upperparts (no white horseshoe on uppertail-coverts) and lacking strongly contrasting underparts and underwing; immature of present species in ventral view may resemble immature gannet, but is smaller overall, with usually thinner bill and different-coloured feet; relatively large dark eye and bill colour of second-plumaged immatures may recall otherwise highly characteristic Papasula abbotti.

    Voice

    Emits fast “rah-rah-rah-ráh-rah-rah” calls when returning to colony. Male also gives harsh rasping calls, distinctive within the family.

    Habitat

    Strictly marine and largely pelagic. Breeds on islets with abundant vegetation.

    Food and feeding

    Mainly flying-fish (Exocoetidae) and squid (Ommastrephidae); mean prey length 8·8 cm. Food caught by plunge-diving; flying-fish also taken in flight, especially if chased to surface by underwater predators. Typically feeds in flocks. Dives are generally fairly shallow, often < 1 m#R and c. 5 m maximum depth on average, but perhaps also employs underwater pursuit swimming#R. Frequently suffers piracy from frigatebirds (Fregata). Partially nocturnal feeding habits, possibly because squid come to surface at night; with moonlight may fish all night. Often alights on ships, using them as vantage points. Reversed sexual size dimorphism less marked than in other boobies, females being only 15% larger than males#R, and its significance in this species does not seem related to division of labour when nesting as females show only slightly more parental commitment than males#R.  

    Breeding

    Not seasonal in most of range, and may start breeding in any month. Breeding can be intermittent; on Johnston Atoll, S of Hawaii in Pacific Ocean, skipped seasons reportedly more likely during El Niño years, when water temperatures higher, suggesting that environmental factors are involved#R. Co-operative polyandry reported on Dong I (Xisha Archipelago), in N part of South China Sea, where stable trio (two males, one female) observed to breed five times in four consecutive years, 2004–2007, the three sharing breeding duties equally#R. Highly gregarious, forming large colonies. Stick nest placed on tree or bush, and also recorded as nesting on ground or on wall. Clutch single egg, size 60 mm × 38·5–41 mm (nominate race, Brazil)#R; incubation period c. 45 days; chick has whitish down; fledging period 100–139 days; post-fledging care generally c. 190 days; in study on Dong I, juveniles took mean 118 days to become independent (post-fledging survival 96%), made progressively longer foraging trips, probably mainly to develop foraging skills (94% of food supplied by parents in early juvenile stages), and foraged for themselves mostly from 60 days after fledging, at least 60% of fledglings still alive 20–84 days after independence#R. Age of first breeding probably 2–3 years. Known to have lived for nearly 23 years in the wild.

    Movements

    Pantropical distribution and long foraging trips obscure any regular movements, but probably mainly dispersive over tropical oceans; juveniles undertake widest-ranging movements, sometimes 100s of km from nearest land. May forage up to 150 km from colony, often setting off before dawn and returning after dark. Has wandered N to E USA coast (first recorded 1963, in Florida, but since observed N to South Carolina and W to Texas, with most records mid Mar to Oct)#R#R, S to Easter I in SE Pacific#R and N to California (first recorded 1975, late May to mid Nov, mainly in autumn)#R, has appeared occasionally in the SE Atlantic at St Helena#R and on coasts of Namibia and South Africa#R. Recorded off Nova Scotia, Canada, in Sept 2014#R. An adult on Raso in Mar 2013 was first record for Cape Verde Is#R (and breeding was confirmed there in Jun 2016)#R, with two recent records from Surinam, in Jun 2012 and Aug 2013#R, and one in the Azores, in Aug 2015#R. Single vagrants have also appeared recently in W Mediterranean; in Spain and S France; and in Canary Is#R#R.

    Status and conservation

    Not globally threatened (Least Concern). One of most abundant and widespread of all sulids, but population widely scattered on myriad of small islands through tropical seas; few colonies protected. As result of its tree-nesting habit, has suffered greatly from habitat destruction, especially in W Indian Ocean, where at least 12 colonies lost in last 100 years; also in S Atlantic, where just 100 pairs remain. Recently confirmed breeding in NE Atlantic, on Raso, in Cape Verde Is (see Movements). Still numerous in Caribbean (14,000 pairs), Galapagos (250,000 pairs, including 140,000 on Genovesa), C & E Indian Ocean, where 12,000 pairs on Christmas I and similar numbers in Chagos archipelago (where population is currently expanding in numbers and range, colonizing new islands)#R, 30,000 birds on Cocos (Keeling) Is, and in S Pacific; population of Hawaii recovering from earlier loss of habitat. Important colonies on the Cocos Is are confined to N Keeling, although species was formerly widespread throughout archipelago: harvesting for food by humans has occurred since islands were first settled in 1827 and still accounts for an estimated 2000–3000 birds per year, possibly 10,000 in some years, although it is now illegal. Nevertheless, Cocos Is population shows no current long-term decline, although it fluctuates considerably in relation to cyclonic events#R. Other factors limiting numbers are egg-collecting, poaching, predation by rats (Rattus) and disturbance caused by tourism. Population greatly reduced in historical times, but, given vast breeding range, still large, probably numbering well over 1,000,000 birds.

    Recommended citation

    Carboneras, C., Christie, D.A., Jutglar, F., Garcia, E.F.J. & Kirwan, G.M. (2019). Red-footed Booby (Sula sula). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/52624 on 22 November 2019).