“On the 28th February 2011, I had the opportunity to re-visit and explore the depths of a limestone cave network in Sarawak, East Malaysia. The most prominent inhabitants of this cave were the bats, with at least four species observed in colonies of varying population sizes/densities and occupying different sections of the undulating cave roof and walls. Another winged vertebrate which shares this cool, damp and dark habitat was a loose colony of the Mossy-Nest Swiftlet (Aerodramus salanganus) (left). Just like their bat neighbours, these birds employ echolation to navigate inside the caves. This species has a habit of collecting fresh moss to cushion their nests, which are always securely situated upon a concave ledge (Lim & Earl of Cranbrook, 2002) (below left).
“As I proceeded deeper into the cave, I chanced upon two eggs of this swiftlet, as the parents may have flown outside briefly in search of food and drink (below right). The typical breeding season for this swiftlet is between March to June (Myers, 2009). In Borneo, there are two other swiftlets that inhabit the interiors of caves, namely the White-Nest Swiftlet (A. fuciphagus) and Black-Nest Swiftlet (A. maximus). Both are also capable of echolocation, but unlike the Mossy-Nest Swiftlet, nest on vertical walls instead. Their nests are constructed out of solidified saliva and have been harvested, traded and consumed as ‘bird’s nest’ for centuries – hence the revered economic value (Lim & Earl of Cranbrook, 2002).
“Since the nests of the Mossy-Nest Swiftlet are neither edible nor marketable, there appears to be little incentive to warrant detailed studies of its behaviour and ecology. Nevertheless, let us not ignore its ecological role as an efficient aerial insectivore, as well as a contributor to the nutrient pool within the cave ecosystem whenever it defecates. Just avoid standing below the swiftlet when this happens!”
Dr Leong Tzi Ming
10thth March 2011
“I am grateful to Prof. Indraneil Das for kindly facilitating my exploration of the limestone cave and hosting my brief stay in Sarawak. I also thank Dr. Lim Chan Koon for sharing his in-depth insights into the fascinating biology of various cave-dwelling swiftlets in Borneo.”
1. Lim, C. K. & Earl of Cranbrook, 2002. Swiftlets of Borneo – Builders of Edible Nests. Natural History Publications (Borneo), ix + 171 pp.
2. Myers, S., 2009. A Field Guide to the Birds of Borneo. New Holland Publishers, 272 pp.