Predator-Prey Interactions of Adult and Prefledgling Bank Swallows and American Kestrels

Abstract

Young bank swallows (Riparia riparia) are subject to aerial predation. Freer recently documented that American kestrels (Falco sparverius) will atack swallows in flight and at their burrows. Observations made at a number of colonies support the contention that kestrels are frequent aerial predators on these birds. The hunting strategies of the kestrels and the anti-predator behavior of bank swallows are described and their possible adaptive significance is discussed. The number of interactions observed suggests that kestrels may frequently visit bank swallow colonies and prey on their nestlings. The impact of this predation appears to be minimized by a vocal alarm system, which stimulates the retreat of young back into their burrows, and a within-colony synchronization of reproductive efforts, which minimizes the period of vulnerability.