Function and evolution of song in a duetting neotropical passerine, the gray-breasted wood-wren (Henicorhina leucophrys)

• Main Author: Dingle, C. E.
• Published: University of Cambridge 2009
• Subjects: 591.5
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598549

The aim of this study was to understand the function of song and its role in the speciation process in a duetting Neotropical passerine, the gray-breasted wood-wren (<i>Henicorhina leucophrys).</i> This species lives in the dense understory of mid-elevation cloudforests throughout the Andes and up into southern Mexico. Gray-breasted wood-wrens sing sex-specific songs, either as solos or as complex duets, with the male and female of a mated pair alternating their songs with variable degrees of coordination. Males sing more than 50 different song types, while females sing at least 15-20 song types. Duets are initiated by males and females at equal rates. Using playback experiments simulating intrusions by paired and single birds, I show that males and females sing to advertise their partner’s mated status and to repel potential rivals. These results show that duets reflect conflict between the sexes rather than cooperation between the pair. I studied song variation in two subspecies of the gray-breasted wood-wren which occupy different habitats in the Ecuadorian Andes. I found that the subspecies sing significantly different songs and showed that these differences are driven by acoustic differences in their preferred habitats – loud cicada choruses in the habitat occupied by one subspecies have caused that subspecies to sing at a lower frequency in order to be heard over the noise. Where the two subspecies come into secondary contact, their songs are more different from each other than in areas where they do not meet. This suggests that there is a cost to mating with the wrong subspecies and that selection has driven the songs apart in order to prevent such an occurrence. This result provides the first convincing case of character displacement in bird song and strong evidence that song divergence acts as a barrier to gene flow between these two subspecies.