In the Urban Forest blog, Siyang relates his encounter with a Pacific Swallow’s (Hirundo tahitica) nest complete with three chicks. The nest was plastered to a wall in a lonely corner of the National University of Singapore’s Kent Ridge campus (left).

“… a cup shaped nest made of mud with the inside lined with soft bedding-like feathers. Three little heads looked down at me when I was curiously looking at it. Baby swallows!

“The parents dun take kindly to passersby. It attacked Juanhui (missing by inches), directly at Lionel and me (had to duck away) when we walked pass below the nest on separate occasions. Still, I do hope those chicks survived and fly free in the sky soon.”

These Pacific Swallows are common residents in Singapore. They are seen all over the island and have no problems nesting around human habitation. They build their nests around the first half of the year. The nest is a half-cup made of mud stuck to a rough vertical surface, in this case the wall of a building structure.

Both partners assist in mud collection, digging the damp mud with their bill and transporting the pellets back to the nesting site (below). There, the mud is stuck to the vertical surface to create a base from which the side of the nest is developed. Numerous trips are needed before the nest is finally completed in a few days to a few weeks.

The mud is often mixed with vegetable fibres and the nest is lined with dry grass, lichens and feathers. In the case of feathers, they are often caught in flight or collected from the surface of water-bodies.

These nests are recycled year after year after some repairs.

The bird lays a clutch of two to three eggs with the female incubating them for 17-22 days. The chicks have characteristic pale yellow oral flanges enclosing the orange mouth cavity (top). These function as targets for the adults feeding the chicks. This is also seen in Eurasian Tree Sparrow (Passer montanus) and Oriental White-eye (Zosterops palpebrosus).

The food brought for the chicks are in a compressed ball of insects. A ball may serve more than one chick when they are young but as they get older, each may be fed a ball of insects. It take about 20 days for the chicks to fledge, after which they return to the nest at night for several more days. The feeding of the juveniles (right) has been posted earlier.

Some of these swallows have been recorded to live up to seven years.

Images by Siyang (nest with chicks) and Chan Yoke Meng (collecting mud and feeding juveniles).

References:
Spittle, R.J. (1949). Nesting habits of some Singapore birds. Bulletin of the Raffles Museum 21:184-204.

Turner, A. K. (2004). [‘Family Hirundinidae (Swallows and Martins)’]. Pp. 602-685 in del Hoyo, J., Elliott, A. & Sargatal, J. eds. Handbook of the birds of the world. Vol. 9. Cotingas to Pipits and Wagtails. Barcelona: Lynx Editions.

I work in the Singapore Botanic Gardens and the Grey-rumped Treeswifts (Hemiprocne longipennis) do well here. Outside the Visitor Centre they perch in the big trees, they always select the tallest branches, often dead exposed ones. From there they sally for insects, and I presume they nest, although I have never had a chance to study it. But in 2006 I got the chance. A friend who comes in our shop told me about a nesting pair she had near her home, a high rise development nearby off North Buona Vista Road.

The treeswifts form a small family, Hemiprocnidae in the Apodiformes order which includes three families: treeswifts, swifts and (maybe a bit surprisingly) hummingbirds. Hemiprocnidae is only in the Oriental region and only has one genus with four species. Treeswifts differ from true swift in that they can and often do perch on branches, they are arboreal birds. True swifts form a much larger family (92 species world wide); they spend almost all their time in the air, they even sleep and mate on the wing. They cannot perch on a branch or on the ground, they can only grab a vertical surface with their small, weak feet; therefore they only land when they have to nest, which they do in caves or under cliffs, or under man-made structures like buildings and bridges (a few species fly into tree holes), using the only building material available to them: their own saliva and feathers.

The Grey-rumped Treeswift forms a superspecies and was previously considered conspicific with the Crested Treeswift (H. coronata). The former occurs in the Sunda subregion plus Sulawesi, the latter replaces it in Thailand and Indochina into India. Incredibly, for these widespread and fairly numerous two species there are big gaps in our knowledge of their nesting biology, neither incubation nor fledging periods have ever been recorded (Handbook of Birds of the World, Vol. 5, p. 465). The North Buona Vista pair built a small nest in some dead branches in a tall tree, some 20 meters off the ground, it was clearly visible from the balcony of a nearby building. The nest was a tiny cup made of hardened saliva mixed with minute pieces of what appeared to be bark or moss (above, chicks in nest). When the adult sat on the nest the whole structure was invisible, covered by the bird! We know that the egg was laid somewhere between 7th -11th May 2006, it hatched 3rd of June. I visited the nesting site with my son Adam on 5th June. He took some photos with his digital compact camera - the chick was then 2 days old. Both female and male (recognisable by the rufous ear coverts) took turn attending to the chick and feeding it with a regurgitated substance, presumably somewhat pre-digested insect matter. I visited the site again on 16th June. The chick was bigger of course but still covered in down, still fed regularly and still sheltered completely by one of the parents between feeds. Later on it started to develop feathers, it moved away from the tiny nest and perched on the branch on its own, feeding became less regular. On 1st of July 2006 it left the nesting branch, almost the same hour in the afternoon that it hatched. We now know the fledging period of the Grey-rumped Treeswift: it is exactly 4 weeks! (above, male tending to young; below pair tending to young) So, how is the Grey-rumped Treeswift doing? Well, none of the four treeswifts are globally threatened with extinction. However, the HBW states that ‘Pesticides are suspected to be behind recent population declines in Singapore’. David Wells states something similar: ‘Declining in some suburban areas, including on Singapore main island where the largest party of non-breeders recently recorded was of only five birds’ (The Birds of the Thai-Malay Peninsula Vol. 1, p. 473).

Luckily, in the Singapore Botanic Gardens we still have many more treeswifts than that. The treeswifts like to interact and fly around high together while calling, often late in the day; it is not unusual to see 10-12 birds at one time during those occasions. One evening during ‘winter’ a few years back I was at the exercise ground around 6 pm when a Japanese Sparrow-Hawk (Accipiter gularis) flew quickly by towards the rainforest area, and out of the blue congregated a large flock of treeswifts to mob it. I managed to positively count 35 individuals in the air at one time, but there must have been more, maybe 40. They swerved around excitedly for a few minutes after the hawk had disappeared before they gradually dispersed, many settling around the edges of the rainforest.

Text by Morten Strange; images by Adam Strange.