The Food of the Swift

Abstract

Swifts feed on air-borne insects, but take more varied foods than those in true aeroplankton, since they often feed close to ground, to trees or to open water. They seek out places where air-borne insects are abundant; this varies with weather. 81 food balls brought by parent birds to young were analysed. Homoptera and Diptera were specially common, while Hymenoptera, Coleoptera and Araneida were well represented. A huge variety of spp. were taken, indeed swift probably eats more spp. than any other British animal. Specific content of meals differed greatly. Some contained a large number of 1 sp. Insects of more than 10 mm and less than 2 mm were rarely taken. In fine weather, those of 5-8 mm were usually selected in preference to those of 2-5 mm, but latter were taken in large numbers in poor weather, when larger sorts were scarce. There was no evidence from meals that swifts avoided mimetic or warningly colored insects; syrphids were quite common. But a published record shows that swifts preying on hive-bees took only drones.