Pacific Swift
Apus pacificus

– small near-passerine, larger than sparrow, same size as Common Swift
– very rare vagrant to WP, Asian origin
– diurnal migrant, always airborne thus nocturnal as well
– migrates singly or in small, very loose flocks

BIF421_MPU_PMA2485_110521_pswift_mng_khlerlen-gol
Pacific Swift Apus p. pacificus
BIF0421, 21/05/2011, Khlerlen Gol, Mongolia, Mathias Putze
– tail slightly longer than in Common Swift
– blackish tail and uppertail coverts contrasting to sooty body and wings
– white rump extending to rear flanks (more restricted to back in White-rumped Swift)

BIF524_MPU_I1Q8136_140613_pswift-pacificus_mng_choibalsan
Pacific Swift Apus p. pacificus
BIF0524, 13/06/2014, Choibalsan, Mongolia, Mathias Putze
compared to Common Swift:
– underside scalier
– longer tail with deeper fork
– white throat patch larger but more diffuse (well defined in White-rumped Swift)

BIF525_MPU_I1Q8179_140613_pswift-pacificus_mng_choibalsan
Pacific Swift Apus p. pacificus
BIF0525, 13/06/2014, Choibalsan, Mongolia, Mathias Putze
– secondaries without white trailing edge (shown by White-rumped Swift)


Pacific Swift Apus p. pacificus
BIF0526, 13/06/2014, Choibalsan, Mongolia, Mathias Putze
– if only seen from below it resembles Pallid Swift, but note darker colour, more contrasting underwing coverts and more pointed wings


Pacific Swift Apus p. pacificus
BIF0422, 06/06/2011, Ichchet, Mongolia, Mathias Putze

voice:
– most common a two-syllabled piercing ‘scream’
– the first part is a sustained, fine modulated slight overslur -> Common Swift -> Pallid Swift
– the second part is a phrase of fast similar vertical elements (trill)
– the trill is narrower spaced in males (faster)


Pacific Swift Apus p pacificus, AD F, call in flight
BIF0423, 07/06/2013, Tsetserleg, Mongolia, Patrick Franke


Pacific Swift Apus p pacificus, AD M, call in flight
BIF0424, 07/06/2013, Tsetserleg, Mongolia, Patrick Franke

comparison species:
Common Swift (a) (v)
Pallid Swift (a) (v)
Alpine Swift (v)
White-rumped Swift (v)

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