Is "banging" an antipredator behaviour in Common Swift (Apus apus)?

Abstract

Prey species show various types of antipredator behaviors to avoid predator attacks. Common Swifts (Apus apus) show specific behaviour where birdsmake almost a full stop during flight - this is referred to as "banging" behavior. This behaviour may be directed towards a conspecificswhich, for example, enters a nesting or a roosting site, or clings to a wall of a building. The bird showing this behavior is usually accompanied by conspecifics, which also copy its flight pattern. Actual explanations for this behavior are often inconsistent and unclear. This study has reconsidered such explanations and focused on the novel role of this behaviour as a potential antipredatory adaptation against the Common Kestrel (Falco tinnunculus). Observations of Common Swift behaviour were carried out inMay-September 2014 and May-August 2015 in Opole, SW Poland, giving 1,367 observations of nesting/roosting activities, 868 observations of "banging" behavior and 37 attacks of kestrels on swifts. Therewas a negative correlation between the number of successful hunting attempts and the number of Common Swifts showing banging behaviour. The study covers different aspects of banging behavior andmajor factors correlatingwith its occurrence.