This article presents breeding data for colonies of the Coastal Australian Swiftlet, Aerodramus terraereginae terraereginae, on the Family Islands, off the coast midway between Townsville and Cairns, Queensland, Australia, obtained on visits to the islands between 2015 and 2022. This information is supplemented by published data going back to 1908 to provide an indication of population trends over a time span of 114 years. While colony sizes appear to have fluctuated significantly from year to year, possibly in response to cyclone impacts, the island populations of this swiftlet have remained fairly stable over the longer term – despite well-documented population declines in their main food source, insects. The breeding season of the island colonies was found to extend from July to April, with some variability between colonies. Peak egg-laying occurred between November and February. We also provide a population estimate for a previously unrecorded Australian Swiftlet colony on nearby Hinchinbrook Island. This colony, which shares its sea cave with a large colony of insectivorous bats, is by far the largest known island colony of the species. Daily time- lapse photography on a swiftlet colony on Dunk Island in 2016 and 2017 revealed that up to three sequential clutches, each comprising a single egg, were laid per nest during the breeding season. Incubation of the second and/or third egg by a nearly- fledged older sibling confirmed that sibling incubation, which had previously been observed in the Chillagoe Australian Swiftlet, A. terraereginae chillagoensis, also occurs in the coastal subspecies.