The influence of nest harvesting upon nest construction and egg‐laying was studied in the White‐nest Swiftlet Aerodramus fuciphagus and the Black‐nest Swiftlet A. maximus in Singapore. A study of nestling energetics allowed an estimate to be made of adult foraging abilities. The energy and nutrients required for nest construction are easily acquired by foraging but the females may face a shortage of energy or depletion of stored lipids during egg formation. Removal of nests did not affect the size or quality of replacement nests or clutches, but may aggravate the lipid shortage. Nest removal did reduce breeding success in replacement nests and, in the White‐nest Swiftlet, disturbance to the colony resulted in an increased laying interval between first and second eggs. Our results indicated that commercially exploited colonies should be left unharvested for the middle part of the breeding season to allow a period of successful reproduction.

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