Impact of red-winged blackbirds on singing activities of long-billed marsh wrens

Abstract

Male long-billed marsh wrens prefer to sing from the tops of cattails, but red-winged blackbirds force wrens to sing from lower perches on cattails. The response of marsh wrens to redwing aggression declines with increasing distance from redwings. Marsh wrens that are frequently exposed to redwing aggression respond less strongly to redwings at intermediate redwing–wren distances than wrens that rarely encounter redwings. This is probably because marsh wrens habituate to redwings and learn to respond only to those situations when redwings present an immediate threat.Marsh wrens responded strongly to redwings but little or not at all to nine other species that approached them. This species-specific response is most likely associated with redwing–wren aggressive interference. It is proposed that by suppressing marsh wren singing activities redwings might depress the mating success of male marsh wrens that defend territories near redwing breeding areas.