Palau Nightjar Caprimulgus phalaena Scientific name definitions

21–23 cm. Previously treated as conspecific with C. indicus (no geographical overlap). Fairly small to medium-sized, greyish-brown nightjar with chestnut-brown on mantle, back and central tail feathers, white throat patch, buff-spotted wing-coverts with brownish centres, no collar on hindneck, white tips to all but central tail feathers and small white patch on four outermost primaries in male; in female these areas are chestnut-brown; undertail and underwing-coverts almost all black.

Until recently considered conspecific with C. indicus and/or C. jotaka, being closer in geography and morphology to the latter, but differing in much smaller size, with wing mean 160·2 (n=6) vs 204·5 (n=10), effect size 7 (3); largely black vs buffy-rufous-and-dull-grey-barred underwing-coverts and undertail (2); rufous vs stony-white flecking and tinge on feathers of chin, throat, crown, scapulars, back and tail (2); proportionately smaller white marking in wing and on tail tip (ns[1]). Monotypic.

Palau Is.

Reported variously in the literature as ‘an accelerating chuck-chuck [song] ... when perched; in flight a karump karump-like call’, or ‘a long succession of harsh percussive whistles, each with a downward inflection, two or three per second ... In group singing this song is mellower and is speeded up into a roll which is uninterrupted for minutes at a time’ or ‘a series of knocking sounds, like a small hammer striking hard wood; pitch and cadence rise, tawk – tock – tac-tac-tac-tac-tac [song  ]; also a loud, harsh screech, kreek, kree-kreek’. Although it is slightly unclear whether the first account truly refers to the Palau population, rather than to C. indicus or C. jotaka, the two latter descriptions were made by observers with field experience on the islands. Also mentioned, again through direct observations on Palau, is a ‘call, given in flight, especially when birds are chasing each other, ... a rasping snore of one syllable’. Heard at least Nov–May.

Not globally threatened. Currently considered Near Threatened. Confined to the Palau Is (where known from at least Arakabesan, Babelthuap, Koror and Peleliu). No population estimate available, but given the species' very small range (380 km²) total population is presumed to be small, and has been precautionarily suggested to number no more than 1000–2500 mature individuals. Described as uncommon and declining by the late 1970s (it had been apparently commoner in the first part of 20th century), but it is unclear if the population is currently in decline, as the species is thought to be tolerant of some habitat modification, and existing levels of land-use change and habitat degradation might have only minimal impacts; BirdLife provisionally suspect numbers to be stable. Potential arrival on the island of invasive predators such as brown tree snake (Boiga irregularis) could present a significant future threat.