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NIGHTJARS (CAPRIMULGIDAE; 10 SPECIES) Worldwide family of nocturnal,

insect-eating birds that sleep by day and rely on cryptic plumage to avoid detection and

predators. Ages/sexes differ slightly in most species (mainly in tail pattern, and females more

often have rusty morph than males); like adult in 1 year. Typically nest on ground.

SHORT-TAILED NIGHTHAWK  Lurocalis semitorquatus 20–21cm. Humid

forest and edge, especially along rivers and streams in lowlands; roosts and nests

in forest canopy. Singles or pairs emerge at dusk to feed low over forest canopy

and along edges; erratic flight may suggest a large bat rather than Chordeiles

nighthawks. Distinctive, with fairly large size, short tail, overall dark plumage

(no white wing bands). Sexes similar. SOUNDS: In flight a sharp, slightly liquid

cluck, singly or in short quick series, g’wik and gwik whik-whik; rougher gwirrk

in interactions. STATUS:  Uncommon to fairly common on both slopes, to

1200m. (Mexico to S America.)

LESSER NIGHTHAWK  Chordeiles acutipennis 20.5–23cm. Open and semi-

open areas with scattered trees, forest and edge, beaches, mangroves, towns;

roosts on tree branches and ground, nests on ground. Mainly an aerial feeder,

flight fairly erratic with bursts of quick flicking wingbeats and short glides on

wings held in distinct V; flies low to high, mainly fairly low on breeding

grounds, flocks often high overhead in migration. Also hunts from ground and

perches, flushing off roads like typical nightjars. Post-roost flights of 100s seen

locally in migration and winter. Only real ID concern is with Common Night­

hawk; note that both species when perched usually show white on bend of

wing, unlike other Costa Rican nightjars. Common has longer, more pointed wings, flight stronger and

less fluttery with deeper, more rangy wingbeats; white wing band farther from wing-tip and slightly

longer, extends across 5 primaries (only 4 primaries on Lesser); lacks bold pale barring across inner

primaries. On perched Lesser, note grayish band of fine barring on breast (lacking on Common), white

wing band of male Lesser lies under tip of tertials, vs. forward of tertials on Common; female Lesser has

buff wing band. On both species, wing-tips can project past tail at rest, more often on Common.

SOUNDS: Song (spring–summer) from ground or low perch a churring trill, swells quickly and fades

abruptly, urrrr..., can go on for minutes, typically in bursts of 7–13 secs, with pauses of 1–3 secs; can be

mistaken for Cane Toad Rhinella marina, which is lower-pitched, more pulsating. Bleating whik in flight,

mainly in interactions. Flushed winter birds usually silent. STATUS: Fairly common breeder locally on

Pacific slope, especially near coast; more widespread and locally numerous Sep–Apr on both slopes,

mainly below 1200m. (Mexico and sw. US to S America.)

COMMON NIGHTHAWK  Chordeiles minor 23–24cm. Breeds locally in drier

open and semi-open areas of foothills, from savanna to marshes, airfields;

migrants occur in any habitat; roosts mainly on tree branches, nests on ground.

Habits much like Lesser Nighthawk but flight stronger, less fluttery; in breeding

season often flies much higher. Only real confusion possible is with Lesser

Nighthawk (which see for ID criteria); also note that Common undergoes wing

molt in S America, whereas Lesser molts during late summer–fall in Costa Rica.

Plumage tones more variable than Lesser, with local breeders smaller and rustier

overall than boreal migrants, which vary from dark overall to relatively pale and

sandy gray. SOUNDS: Call in flight (mainly breeding season, also migration) a sharp nasal beenk or peehn;

in display flight, male stoops steeply and produces loud rushing boom at bottom of dive. STATUS: Fairly

common breeder late Mar–Aug locally on Pacific slope, mainly 400–1000m; more widespread and

sporadically fairly common to common in migration, Sep–Nov, Apr–May, mainly below 1500m. (Breeds

N America to Panama, winters S America.)