Neighbour recognition by resident males in the banded wren, Thryothorus pleurostictus, a tropical songbird with high song type sharing

Several studies and reviews have suggested that the ability to discriminate between neighbours and strangers decreases as neighbour song repertoire si ze and song type sharing increase. We tested the recognition capabilities o f territorial. male banded wrens by comparing the aggressive approach respo nses of focal birds to three playback treatments: shared song types sung by an adjacent neighbour (neighbour song), shared song types sung by unfamili ar birds (mimic song), and unshared song types sung by unfamiliar birds (un familiar song). All three treatments for each male were broadcast from the same location on the territorial boundary shared with the appropriate neigh bour. As expected, focal males responded non-aggressively to the neighbour treatment and aggressively to the unfamiliar song treatment. The approach r esponse to the mimic treatment was statistically indistinguishable from the unfamiliar treatment and significantly higher than the neighbour treatment , suggesting that most males were able to recognize unfamiliar singers even when the song types played were very similar to those of their neighbours. The relative strength of responses to the mimic varied: some males treated the mimic song with low aggression levels typical of responses to neighbou r song. Repertoire sizes of focal and neighbour birds, the fraction of song types shared among neighbouring males, and the similarity of neighbour and mimic song types did not explain this variation. Therefore, within the sho rt 3-min period of our playback experiments, some birds may have used reper toire composition as a recognition cue and confused the mimic with the neig hbour. (C) 2001 The Association for the Study of Animal Behaviour.