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TERNS (LARIDAE; 13+ SPECIES) Worldwide group of waterbirds that resemble gulls

but have pointed bills, shorter legs, and typically are smaller, more graceful, with forked tails.

Unlike gulls, rarely alight on water, mostly feed by plunge-diving for small fish. Ages differ, sexes

similar but males average larger, bigger-billed. Adult appearance attained in 2–3 years; imm.

plumages typically resemble nonbr. adults. Seasonal variation mainly in head pattern.

*SANDWICH TERN  Thalasseus sandvicensis 34–36cm (+ 2.5cm adult tail

streamers). Pacific and Caribbean coasts, at beaches, river mouths, coastal

lagoons, over inshore waters. Often in flocks with other terns, gulls, skimmers.

Distinctive, medium-size tern with shaggy crest, white body, slender black bill

tipped yellow on adult, black legs. 1st-year bill black with little or no pale tip;

dark spots and chevrons on juv. back soon replaced with plain pale gray. Cf.

Gull-billed Tern. SOUNDS: Grating, screechy and rasping calls, such as krríik

and krrek, distinct from smaller Sterna terns but much like Elegant Tern; 1st-

year has high piping whistles. STATUS:  Fairly common to common nonbr.

migrant on both coasts, mainly Sep–May; smaller numbers of imms. occur through summer. (Breeds N

Atlantic, winters to S Atlantic.)

ELEGANT TERN  Thalasseus elegans 35–37cm (+ 4–5cm adult tail streamers).

Pacific. Fairly large tern of marine waters, rocky and sandy coastlines, river

mouths. Often found with other terns, gulls, skimmers, when groups of

Elegants can bunch up tightly and be lost easily among much taller Royal Terns.

Appreciably smaller and more lightly built than Royal Tern but size can be

difficult to judge on lone birds; note much finer bill of Elegant, variable in color

(orange-red to yellow) but often paler at tip (vs. uniform orange on Royal);

longer and shaggier crest, which joins with eye in nonbr./imm. plumages (vs.

eye often surrounded by white on Royal). Often has pink blush to underparts,

unlike Royal and Sandwich Terns; legs rarely orange, mainly on imms. SOUNDS: Grating, screechy, and

rasping calls much like Sandwich Tern, generally higher, scratchier than Royal Tern; 1st-year has high

piping whistles. STATUS: Scarce to uncommon nonbr. migrant along and off Pacific coast, mainly Sep–

Nov, Feb–Apr; rare at other seasons. (Breeds Mexico and s. California, winters S America.)

ROYAL TERN  Thalasseus maximus 43–48cm (+ 5cm adult tail streamers).

Large, orange-billed tern of varied coastal habitats, from rocky headlands and

sandy beaches to river mouths, inshore waters, coastal lagoons. Often in feeding

and roosting flocks with other terns, gulls, skimmers. Slightly smaller and more

lightly built than Caspian Tern, with narrower, more angled wings, and longer

tail, shaggier cap, uniform orange bill (rarely orange-red); lacks solidly dark

underside to wing-tip of Caspian; imm./nonbr. plumages have large ‘bald’

white forehead, unlike Caspian. Cf. smaller, finer-billed Elegant Tern. Legs

rarely orange, mainly on imms. SOUNDS: Adult has clucking krehk and laughing

kewh-eh; also grating and screechy calls similar to Elegant Tern; 1st-year has high piping whistles.

STATUS: Fairly common to common nonbr. migrant on both coasts, mainly Sep–May; smaller numbers of

imms. occur through summer. (Americas.)

CASPIAN TERN  Hydroprogne caspia 51–57cm. Largest tern in the world, a

nonbr. migrant to coastal lagoons, tidal flats, river mouths, rarely over open

ocean. Often rests with groups of gulls, other terns, mainly as singles. Bulky and

broad-winged, lacks long tail streamers. Wingbeats relatively shallow and gull-

like. Note overall size and bulk, very stout red bill with black ring near tip, dark

underside to primaries; juv. has orange bill with dark near tip. Imm./nonbr.

have densely black-streaked crown, lacking large ‘bald’ white crown patch of

other terns. Cf. Royal Tern. SOUNDS: Adult has deep throaty rahrr, quite distinct

from other terns and may suggest a heron; 1st-year has high lisping whistles.

STATUS: Uncommon to rare and local nonbr. migrant on Pacific coast, mainly Sep–Apr in Gulf of Nicoya;

a few imms. may occur through summer; very rare on Caribbean coast. (Worldwide except S America.)