INTRODUCTION
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. 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 and provides a basis for more sophisticated forms of cognition in animal societies. Recognition of social partners has been documented for territorial songbirds, which discriminate between songs of different neighbours as well as between the songs of strangers and neighbours.		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.
CONCLUSION
Long-term recognition of individual neighbours might provide immediate benefits in reproduction. Establishment and defence of territorial boundaries take time that males could spend attracting mates. If males with familiar neighbours can spend more time courting females, it would benefit them to return to their former territories and to remember neighbours.		It thus seems plausible that long-term memory and recall of individual neighbours might represent an evolutionary adaptation in cognitive abilities in migratory species like the hooded warbler.

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