Listening to bird song in temperate regions it soon becomes clear that it is produced, in most cases, by the male of a species. In tropical reigons, females often sing and in some species the pair will even duet. I made some sound recordings of Coraya Wrens (Thryothorus coraya) near Tarapoto (06°28'39.8'' S 76°21'05.9'' W) soon after dawn the other morning. This species engages in antiphonal duetting where both sexes contribute alternative phrases in quick, coordinated succession to produce a ‘final’ song. To our ears this can sound like it is being produced from just a single individual. According to the new Birds of Peru field guide by Schulenberg et al, the Moustached Wren (T. genibarbis) has a near identical song but its distribution is generally allopatric with Coraya Wren and occurs south of the Amazon river and (mainly) east of the Ucayali river. The Coraya Wrens around Tarapoto are difficult to observe but the facial plumage actually looks more like Moustached! At this site they keep well hidden in dense scrub in long-cleared secondary growth. The birds in the sonogram below were not visible during the sound recording but I believe the male bird is producing the rapid phrase of four deeper hoots then two higher pitched whistles, quickly followed by the female’s higher pitched ‘wolf whistle’ phrase. If you look closely just after 5 seconds, you’ll see the female overlaps the end of the male’s phrase.