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BOOBIES (SULIDAE; 6 SPECIES) Small worldwide family of large, streamlined,

plunge-diving oceanic birds. Ages differ, sexes similar or differ in face and bill colors, voice;

attain adult appearance in 2–4 years. Vocal mostly on breeding grounds but can be heard in

feeding interactions.

BREWSTER’S BROWN BOOBY  Sula [leucogaster] brewsteri 68–75cm, WS

135–153cm. Pacific inshore waters. Commonest and most frequently seen

coastal booby, sometimes enters harbors, perches on boats, pilings; nests

colonially and roosts on inshore rocks and islands. Often joins feeding flocks

with terns, shearwaters. Adult distinctive, with sharply demarcated clean white

belly, solidly brown upperparts; male crown pale milky, at times extending to

most of neck, face slaty bluish; female face pale yellow, bill pale pinkish. Juv. has

ghosting of adult pattern, whitish underwing coverts contrast with darker body.

Older imm. has body variably mottled whitish and brown. SOUNDS: Male gives

high wheezy whistles, female gruff brays. STATUS: Fairly common to common off and along Pacific coast,

breeding locally, including Cocos I. (Tropical E Pacific.)

BLUE-FOOTED BOOBY  Sula nebouxii 71–79cm, WS 148–166cm. Pacific

inshore waters; often seen from shore; regularly roosts with Brewster’s Brown

Booby on inshore rocks. Often circles high and feeds by steep plunge dives,

unlike lower, shallower-angle dives typical of Brewster’s Brown. Relatively large

with fairly slender grayish bill, distinctive white hindneck and rump patches,

white center and tip of tail; also note white back scalloping. Bright blue feet

develop in 2nd year; feet grayish on juv. Cf. Brewster’s Brown Booby, imm.

Nazca and Masked Boobies. STATUS:  Irregular, rare to uncommon nonbr.

migrant year-round to Pacific coast, including Gulf of Nicoya. (E Pacific.)

MASKED BOOBY  Sula dactylatra 73–81cm, WS 150–170cm. Pacific and

Caribbean offshore waters, unlikely to be seen from land. Mostly well offshore,

alone or with feeding flocks of other boobies, terns, shearwaters. All ages have

stout yellowish bill (rich yellow on some Pacific adults, cf. Nazca Booby), dark

face, extensively white underwings, black tail (rarely some white at base on

adults). Imms. variable, most have broad white neck collar, often some white on

back and rump; however, some Pacific imms. are wholly dark above, not safely

told from juv. Nazca; adult bill colors start to show in 2nd or 3rd year. Also cf.

Blue-footed Booby, white morph Red-footed Booby. STATUS:  Uncommon

nonbr. migrant year-round to Pacific offshore waters, rare in nearshore waters; rarely reported off

Caribbean coast. (Tropical oceans worldwide.)

NAZCA [MASKED] BOOBY  Sula [dactylatra] granti 73–81cm, WS 150–

170cm. Pacific, offshore waters, unlikely to be seen from land. Habits much

like Masked Booby but tends to favor shelf waters vs. deeper offshore waters of

Masked, and thus more likely to be encountered on day trips. Adult has

diagnostic pinkish-orange bill (beware, apparent orange vs. yellow bill colors

can be affected greatly by lighting), usually some white on base of central tail

feathers; imm. not safely told from darker imm. Masked until white in central

tail or adult bill colors start to show, but averages thicker black underwing

margins; older imm. more often has dark shawl on neck sides vs. clean white

neck of Masked. STATUS: Uncommon to fairly common nonbr. migrant year-round in Pacific waters. (E

Pacific, breeds mainly on Galapagos.)