Using closed-circuit infrared camera to assess biparental provisioning behaviour and foraging pattern of house-farmed swiftlets (Aerodramus sp.)

The house-farmed edible-nest swiftlet (Aerodramus sp.) is monogamous, produces nests from hardened saliva, and uses echolocation to navigate in the darkness. Most previous studies have focused on swiftlet nest building and incubation behaviour, but nestling provisioning behaviour, crucial for the survival of offspring during the breeding season, remains unclear. This study examined the nestling provisioning behaviour of house-farmed swiftlets at a swiftlet house farm in central Peninsular Malaysia. Complete focal video footage of the provisioning phase of swiftlets was analysed in detail. The overall feeding period decreased as the chick grew older. The parents alternately visited their nest 6-14 times a day from dawn to dusk to feed the nestling. The peak of this activity was from 07:00 to 08:00 and between 19:00 and 20:00. Nestling provisioning behaviour differed between pairs. The egg-laying interval of parents with two chicks was longer and affected the development of the second chick since the first chick more successfully competed for food and grew larger in size. Most second chicks with a smaller body size did not survive, because of being either purposely or unintentionally eliminated by the parents or sibling. The smaller-sized second chicks that survived took a longer time to fledge than the first chick; therefore, parents had to increase their foraging effort to ensure the survival of their chick until fledging. These behaviours may be influenced by physiological factors, such as age, experience, individual fitness, and abiotic factors, such as weather and food resources; therefore, different parental strategies may be established during the nestling provisioning phase.