Asian Palm Swift Cypsiurus balasiensis Scientific name definitions

11–13 cm; 8·3–10 g. Very small swift with long thin wings and long, deeply forked tail shorter than that of adult C. parvus and lacking streamer-like emarginated outermost rectrices. Mid-grey upperparts, slightly paler rump; pale grey underparts, underwing-coverts appearing darker, with unstreaked throat. Race <em>infumatus</em> darker, especially on rump and glossy black-brown rectrices and outer remiges, with shorter tail and shallower tail-fork; bartelsorum lacks fringing in juvenile and has lightly streaked throat; pallidor paler than infumatus, rump quite uniform with mantle, tail shorter and less forked than in bartelsorum.

Editor's Note: This article requires further editing work to merge existing content into the appropriate Subspecies sections. Please bear with us while this update takes place.

Sulawesi recently colonized (from S), subspecies not yet determined.

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SUBSPECIES

Cypsiurus balasiensis balasiensis Scientific name definitions

Distribution

most of Indian Subcontinent S of Himalayas, from NE India (S Gujarat and Delhi area) E to area W of Assam hills, Bangladesh and S to Sri Lanka.

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SUBSPECIES

Cypsiurus balasiensis infumatus Scientific name definitions

Distribution

NE India (Assam hills) E to Hainan, and S through SE Asia to Malay Peninsula, Sumatra and Borneo.

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SUBSPECIES

Cypsiurus balasiensis bartelsorum Scientific name definitions

Distribution

Java and Bali.

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SUBSPECIES

Cypsiurus balasiensis pallidior Scientific name definitions

Distribution

Philippines.

Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Primary dependence on fan palms (Livistona, Borassus, Corypha, Areca) but in some areas thatched roofs used as nesting and roosting sites. Forages adjacent to sites, especially over mangroves and paddy, where palms prevalent. Although mainly a lowland species, as are fan palms, recorded to 1000 m in India and Sri Lanka, 1500 m on Java and in China and Myanmar, and 1320 m on Sulawesi. Common even in city parks. Rarest in dense forest, though clearings and edges utilized. Resident over scrub and dry deciduous forest in Mudumalai Wildlife Sanctuary, SW India.

Hemiptera, Coleoptera and Hymenoptera recorded. Detailed Malaysian study of nestling diet (both faeces and bolus) found Coleoptera, Isoptera, Hymenoptera, Diptera, Homoptera and Ephemeroptera, with predominance of flying ants, termites and beetles. Mean open-country foraging height 13·3 m. Frequent in mixed flocks with other swifts and hirundines. Forages particularly actively in evening. Very gregarious; recorded in flocks of up to 1000, though 40 or below more frequent. In S India large numbers feeding on alate rice earhead bugs (Leptocorisa acuta) were most active in early morning, numbers decreasing from 10:00 h onwards as temperature increased.

Most common call  is a pleasant twittering, typically several fast notes interspersed by a longer note “pi-ti-titrtrtr-teee....... pi-ti-titrtrtr-teee-pi-ti-titrtrtr-teee-pi-ti-titrtrtr-teee....”.

Virtually year-round with local variation of peak, mainly Mar–Aug in lowlands and Apr–Jun in hills, India; Dec to early Jul, Malay Peninsula; recorded Oct and Apr, Sumatra, but probably also year-round. Solitary. Typically nests on palm fronds, but where these are scarce will nest in eaves of thatched roofs. Nest is flimsy half-cup of seed-down (Malaysian study revealed sole use of either Ceiba pentandra or Phragmites communis) agglutinated with saliva, c. 10 mm deep × 40–50 mm wide, supporting apron extending over 50 mm above nest; feathers also used, under 5% in Malaysian study, to lesser extent than in C. parvus; eggs not glued to nest with saliva as in C. parvus, perhaps due to deeper, more secure, egg chamber and more continuous incubating habits during stormy weather; sited under palm leaves or near midrib frond of older leaves which hang down almost vertically; nest in Malaysia completed in eight days. Clutch two eggs, though one and three recorded, mean 1·93 in Malaysia; both sexes incubate for c. 78% of time, though incubation continuous during inclement weather; mean feeding interval 45 minutes, shortest early morning and longest midday; adults incubate in vertical position; mean period for last egg 18 days; in two-egg clutches one-day interval between eggs hatching; young initially blind and naked, primary feathers in pin on day 6 and split on day 14, eyes opening on day 7 and movement in nest vicinity on day 14; young cling to apron when nest becomes too full; mean nestling period 28·5 days. Overall egg success 38%. Two clutches recorded in 46% of nests, with interval between first brood fledging and start of second clutch 8–26 days.

Not globally threatened (Least Concern). Common to locally abundant. Least common where fan palms at lowest density. May be absent where palm crowns vigorously cut back, perhaps due to loss of roosting sites. Apparent range expansion in parts of Wallacea: first recorded in 1978 in S & SE Sulawesi, where now quite common; single record from Talaud Is of three birds in Sept 1995, presumably referring to birds of race pallidor; report of many birds at Kapan, Timor, in Jan 1990 would, if confirmed, imply a major range extension.