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Résumé :
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1. Swifts feed on air-borne insects, but take more varied foods than those in the true aeroplankton, since they often feed close to the ground, to trees or to open water. 2. They seek out places where air-borne insects are abundant; this varies with the weather. 3. Eighty-one food balls brought by parent birds to their young were analysed. Homoptera and Diptera were specially common, while Hymenoptera, Coleoptera and Araneida were well represented. A huge variety of species was taken, indeed the swift probably eats more species than any other British animal. The specific content of the meals differed greatly. Some contained a large number of one species. 4. 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 the latter were taken in large numbers in poor weather, when larger sorts were scarce. 5. There was no evidence from the meals that swifts avoided mimetic or warningly coloured insects; syrphids were quite common. But a published record shows that swifts preying on hive-bees took only the drones.
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