Conventional signals impose costs on senders through receiver retaliation rather than through investment in signal production. While several visual conventional signals have been described (mainly 'badges of status'), acoustic examples are rare; however, several aspects of repertoire use in songbirds are potential candidates. We performed interactive playback experiments to determine whether song-type matches (responding to a song with the same song type), repertoire matches (responding to a song with a different song type, but one in the repertoires of both singers) and unshared song types serve as conventional signals during male-male territorial interactions in banded wrens, Thryothorus pleurostictus. Our results demonstrate that these three signals incite varying levels of receiver aggression: song-type matches induce faster approach than do repertoire matches, and repertoire matches induce faster approach than do unshared song types. Production costs do not differ, while the receiver response does. Because territorial banded wrens approach opponents who signal aggressively, such opponents risk attack. This system will punish and prevent cheaters, as weak males signalling aggression will be subject to escalation by stronger or more-motivated opponents.

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This paper presents the first detailed study of the timing and breeding success of an apparently declining population of blue penguins (Eudyptula minor) on the West Coast, South Island, New Zealand. Nest contents of 138 natural burrows and 19 nest boxes were determined at regular intervals during the 2006 breeding season. Hatching, fledging, and overall breeding success rates were comparatively high at 78.9, 83.9, and 66.2%, respectively, suggesting that the apparent population decline cannot be explained solely by low breeding success. With 1.18 fledglings produced per pair, productivity was lower than on the east coast of the South Island, possibly due to the absence of double clutching. The high incidence of road kills suggests that road traffic may be a major contributing factor to the decline of the blue penguin population in the study area.