ALARM CALLING IN SRI LANKAN MIXED-SPECIES BIRD FLOCKS

It is suggested that birds in mixed-species flocks may be particularly aware of aerial predators for two reasons: a “numbers effect” whereby nongregarious species are more aware of predators when surrounded by large numbers of other species; and an “information effect,’ whereby species differ in the information available in their alarm calls, leading to an accumulation of information in a mixed- species flock.