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POTOOS (NYCTIBIIDAE; 3 SPECIES) Small neotropical family of large-headed

nocturnal birds that pass the day roosting cryptically on branches and stumps. Ages differ

slightly, with paler and more loosely textured juv. plumage soon replaced by adult-like

plumage; sexes similar. Readily detected at night by brilliant amber eyeshine reflected in light

beams like burning coals; appreciably larger and brighter than nightjar eye reflection.

NORTHERN POTOO  Nyctibius jamaicensis 38–43cm, WS 91–101cm. Varied

forested and semi-open habitats, from dry forest and mangroves to clearings in

humid forest, farmland, even villages and towns; nocturnal. Roosts at mid–

upper levels in trees, often in rather exposed situations and relying on its cryptic

plumage. Hunts more often from low to mid-level perches, including fence

posts, branches over rivers, less often high perches such as emergent snags, radio

antennae. Hunting birds perch upright and sally out for insect prey, often

returning to same perch like a giant nocturnal pewee. Much larger than

nightjars, and in flight as likely to be mistaken for a large hawk (much longer-

tailed than owls); Common Potoo averages smaller and darker, but safely separable only by voice; little or

no range overlap with Great Potoo. SOUNDS: Song (mainly spring–summer; at other seasons mostly on

calm, often moonlit nights) a low, drawn-out rasp, about 1–1.5 secs, usually followed by 1–6 gulping,

upslurred clucks, WAAAAHRR, wah wah wah, repeated every 6–22 secs. STATUS: Uncommon to fairly

common on n. Pacific slope, locally to 1500m. (Mexico and Caribbean to Costa Rica.)

COMMON POTOO  Nyctibius griseus 36–41cm, WS 88–98cm. Replaces

Northern Potoo away from n. Pacific slope; habitat and habits similar. Averages

smaller and darker than Northern, but safely identified only by voice. Much

larger than nightjars, and in flight as likely to be mistaken for a large hawk

(much longer-tailed than owls). Great Potoo appreciably larger and plainer,

with vermiculated vs. streaked plumage, brown eyes (but eyeshine amber on all

potoos). SOUNDS: Haunting, overall descending and slowing series of (usually

3–7) hollow mournful whistles, often just before dawn: Huwooaah hwoah,

hwoah hwah..., repeated every 8–23 secs. STATUS: Uncommon to fairly common

on both slopes, to 1200m. (Nicaragua to S America.)

GREAT POTOO  Nyctibius grandis 49–58cm, WS 112–125cm. Humid low-

land forest and edge. Roosts and hunts mainly from mid–upper levels, often in

canopy or subcanopy along rivers. Like Common Potoo, hunting birds perch

upright and sally out for insect prey, often returning to same perch like a giant

nocturnal pewee. Common Potoo appreciably smaller with streaked vs. vermic-

ulated plumage, dark mustache, golden-yellow eyes. SOUNDS: Song ‘unpleas-

ant,’ a throat-clearing, overslurred moaning roar, BWAAHr, about 1 sec,

occasionally followed by a quiet 2nd note, repeated about every 8–10 secs;

throatier and unhappier-sounding than Northern Potoo (little or no range

overlap). In flight a shorter, more emphatic woah! STATUS: Uncommon to fairly common on both slopes,

rarely to 1200m. (Mexico to S America.)

OILBIRD (STEATORNITHIDAE; 1 SPECIES) Neotropical family comprising a

single species of nocturnal, fruit-eating bird; nests colonially in caves (nesting unknown in

Central America). Ages/sexes similar.

OILBIRD  Steatornis caripensis 42–47cm. Distinctive, large nocturnal bird of humid forest, where may

be found during day roosting on branches. Feeds in canopy and clearings with fruiting trees, hovering

to pluck palm fruit and wild avocados from outer branches like a giant nocturnal trogon. No similar

species: note long tail, rich rusty plumage spotted with white; also heavy hooked bill, cf. potoos, nightjars;

eyeshine amber, not as brilliant as potoos. SOUNDS: Single birds usually silent, but multiple birds feeding

at night may utter rough gasping sounds and echo-locating clicks. STATUS: Very rare presumed migrant,

found May–Aug at scattered sites from lowlands to highlands on both slopes, most frequently in heavily

birded Monteverde region; might be found almost anywhere in Costa Rica, perhaps especially in foothills.

(S America; migrant (?) to Cen America.)