BREEDING BIOLOGY OF THE EDIBLE-NEST SWIFTLET AERODRAMUS FUCIPHAGUS

A colony of the Edible-nest Swiftlet Aerodramus fuciphagus nesting in a Chinese shophouse in Penang, Peninsular Malaysia, was studied for seven months. Birds bred throughout, but laying was concentrated in the period October to February. Incubation and fledging periods were 23 ± 3 days and 43 + 6 days, respectively. Most young hatched during the dry season. The normal clutch size was two, with many birds laying second clutches (75%) and some third clutches (15-4%) using the same nest. Clutch size showed no variation with clutch order or month. The overall hatching success was 69-0 %, most losses caused by eggs falling from or with the nest. Fledging success was similar for broods of two (625%) and broods of one (59-4%), so that the former were twice as productive. The main loss of chicks occurred when they fell from the nest and were eaten by mammalian predators. There was a tendency for breeding success to decline with successive clutches, but not with month, being highest in November (53-6 %) and February (55-6 %). The growth rate of single chicks and successful broods of two was similar, except that the second chick was more prone to fluctuations in weight. Some second chicks showed evidence of starvation before falling from the nest. Diet was examined by analysis of foodballs regurgitated by mist-netted adults. Foodballs weighed 0–13-1 08 g and, on average, contained over 500 prey items. The main arthropods caught were Hymenoptera (40-8%), Ephemeroptera (26-4%), Homoptera (15-4%) and Diptera (7-7%). Flying ants and mayflies contributed most by weight, although figwasps and mayflies were the most numerous prey items. Only in December did the percentage of moulting mist-netted adult swiftlets fall below 70 %. It appeared that many birds were moulting and breeding simultaneously, although 21% of birds had primaries moulting in two places, suggesting arrested moult. Diurnal activity showed a normal high dawn exodus and dusk inflow of birds, although there was evidence of an increase of birds flying out prior to the dusk inflow. Nest harvesting was continued throughout the study, but most of the marked nests under study were left undisturbed.