Long-term memory of individual neighbours in a migratory songbird

Abstract

CAPABILITIES for long-term memory and recall of information have evolved in non-human animals primarily for special requirements such as for learning species-typical vocalizations and caching food^1–6. Long-term memory of individual social partners has, however, not been demonstrated previously for non-human animals. The ability to recognize individuals has important consequences for the evolution of intricate social interactions^7–11 and provides a basis for more sophisticated forms of cognition in animal societies^12,13. Recognition of social partners has been documented for territorial songbirds, which discriminate between songs of different neighbours^14–16 as well as between the songs of strangers and neighbours¹⁷. Here I show that male hooded warblers ( Wilsonia citrina, Parulinae) not only recognize their neighbours individually by song during the breeding season, but also retain the memory of neighbours' songs after an 8-month period during which they cease singing and migrate to Central America before they return to former breeding territories.