Their call is a loud scream in two different tone pitches, the higher of which issues from the female. They often form "screaming parties" during summer evenings, when 10–20 swifts will gather in flight around their nesting area, calling out and being answered by nesting swifts. Larger "screaming parties" are formed at higher altitudes, especially late in the breeding season. The purpose of these parties is uncertain, but may include ascending to sleep on the wing, while still breeding adults tend to spend the night in the nest. Radar tracking of swifts at their breeding colonies has revealed that they often move together in flocks during their evening ascent and their dawn descent, but fly separately during the subsequent evening descent and the prior dawn ascent, suggesting that this flocking benefits the swifts via cue acquisition and information exchange between individuals or through extending social behaviour.
Their call is a loud scream in two different tone pitches, the higher of which issues from the female. They often form "screaming parties" during summer evenings, when 10–20 swifts will gather in flight around their nesting area, calling out and being answered by nesting swifts. Larger "screaming parties" are formed at higher altitudes, especially late in the breeding season. The purpose of these parties is uncertain, but may include ascending to sleep on the wing, while still breeding adults tend to spend the night in the nest. Radar tracking of swifts at their breeding colonies has revealed that they often move together in flocks during their evening ascent and their dawn descent, but fly separately during the subsequent evening descent and the prior! dawn ascent, suggesting that this flocking benefits the swifts via cue acquisition and information excha?nge between individuals or through extending social behaviour.