Biparental incubation behavior in the domestic house-farmed swiftlets (Aerodramus sp.) in central Peninsular Malaysia

While the breeding biology of the edible-nest swiftlet Aerodramus fuciphagus has previously been studied, research has been limited to direct observations made on cave colonies and details on their incubation behavior remain unknown. Therefore, the purpose of this study was to examine the biparental investment of domestic house-farmed white-nest swiftlets Aerodramus sp. during incubation. This study was conducted at a swiftlet house farm in Bentong, Pahang, central Peninsular Malaysia, from August 2019 to July 2020. An infrared camera connected to a digital video recorder was installed inside the house farm to monitor swiftlets’ daily activities. We determined that the time required for swiftlets to incubate their eggs was 23 ± 0.73 days, while the hatching success rate was 75%. Swiftlets exhibit intermittent incubation with fluctuations in incubation rate from egg-laying until hatching. Both parents incubate equally, with males notably incubate longer at night and females in the morning. The incubation period is influenced by clutch size; parents incubating two eggs have a shorter incubation period than parents that incubating a single egg. Parents alternately exchanged incubation roles when both sexes attended the nest, which often occurred in the early morning before the first emergence period and during nightfall after swiftlets returned to their nests. We identified two behavioral signals during parental exchange: (1) volunteering to move aside and allowing the partner to incubate and (2) being forced by the partner to move aside. The information provided by this study can be useful to bird-nest farmers, who can use it to increase their swiftlet populations by reducing the fatality of nestlings and maintaining a sustainable yield of harvesting.