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LAUGHING GULL  Leucophaeus atricilla 38–43cm. Medium-size, long-winged

3-year gull with dark bill and legs. Commonest gull in Costa Rica, found on

beaches, at river mouths, coastal lagoons, harbors, dumps, over inshore waters;

rarely inland along rivers, at lakes; locally in flocks of 100s, even low 1000s.

Often with flocks of terns, other gulls. Fairly distinctive, but cf. smaller, more

compact, and smaller-billed Franklin’s Gull. Adult has slaty-gray upperparts,

blackish hood with narrow white eye-arcs in breeding plumage, when bill and

legs become reddish. Nonbr. and imm. have smudged dusky mask through

eyes, blackish to dark red legs and bill. Juv. dark brown overall with scaly pale

edgings above, solidly black tail band; soon attains gray back, whiter head and underparts. 2nd-year like

dull adult with more black in wing-tip, sometimes black in tail. SOUNDS: Varied, nasal laughing and

yelping cries; 1st-year has high-pitched whistles. STATUS: Fairly common to common nonbr. migrant to

both coasts; main numbers Sep–Apr, smaller numbers through summer; rare and irregular inland, mainly

fall–winter. (Breeds N America to Caribbean, winters to S America.)

FRANKLIN’S GULL  Leucophaeus pipixcan 35–38cm. Medium-small 3-year

gull with dark bill and legs. Mainly coastal, but also ranges inland and over

inshore waters; spring migrant flocks can number 100s, streaming into lines of

1000s as they pass by; otherwise, singles or flocks occur at river mouths,

harbors, coastal lagoons, inland at lakes and flooded fields. Associates readily

with Laughing Gulls, terns, other waterbirds. Slightly smaller, more lightly

built than Laughing Gull, with smaller bill, more rounded wing-tips, thicker

white eye-arcs; spring adults often have strong pink blush to underparts

(Laughing can have pale blush). Adult wing-tip boldly patterned black-and-

white, unlike Laughing; imm./nonbr. plumages have distinctive blackish half-hood. Black tail band of

1st-winter Franklin’s does not reach to tail sides, but 1st-year Laughing often attains some white tail

feathers. SOUNDS: Yelping and laughing calls higher, more mewing than crowing calls of Laughing Gull.

STATUS: Common to fairly common Mar–May along and off Pacific coast, uncommon to fairly common

Oct–Nov; scarce and irregular in winter. Rare at any season on Caribbean coast. (Breeds N America,

winters S America.)

RING-BILLED GULL  Larus delawarensis 44–52cm. Rare medium-size 3-year

gull with pale gray back. Mainly coastal, at river mouths, beaches, coastal

lagoons. Usually single imms. in association with flocks of other gulls, terns.

Adult distinctive (but very rare in Costa Rica), with yellow legs, pale eyes, neat

black bill ring (no red on bill). 1st-year rather pale overall, with pinkish legs,

whitish underwings, clean-cut black/white tail pattern, pale gray inner

primaries; cf. 2nd-year Smithsonian Gull. 2nd-year resembles duller adult with

more black in wing-tip, often some black on tail, greenish-yellow legs.

STATUS: Rare and irregular nonbr. migrant to both coasts, mainly Nov–Apr.

(Breeds N America, winters to Cen America.)

*SMITHSONIAN (AMERICAN HERRING) GULL  Larus [argentatus] smith­

sonianus 56–67cm. Large 4-year gull with pink legs, pale gray back; male

appreciably larger and bigger-billed than female. Usually single imms. or small

numbers with flocks of other waterbirds at harbors, river mouths, lagoons,

beaches. Adult distinctive (but very rare in Costa Rica), with pink legs, black

wing-tips, pale eyes, variable dusky streaking on head and neck in nonbr. 1st-

year mottled brownish overall, often with paler head, paler panel on inner

primaries in flight, variable pinkish at base of bill. The only regularly occurring

large gull in Costa Rica, but cf. Appendix B. 2nd- and 3rd-years highly variable;

2nd-year pattern resembles smaller 1st-year Ring-billed Gull but messier, lacks clean black/white tail

pattern of Ring-billed. STATUS: Rare to uncommon nonbr. migrant to both coasts, mainly Nov–Apr.

(Breeds N America, winters to Cen America.)