Vocal communication at the nest between mates in wild zebra finches : a private vocal duet?

Bird vocal duets are joint displays where two individuals, generally a mated pair, produce temporally coordinated vocalizations. Duets may contribute to pair bond maintenance, mate guarding or collaborative defence of resources. The degree of coordination between mates and the variety of vocalizations, however, vary considerably. Although only 3–4.3% of bird species have been reported to duet, this may be because studies have generally focused on conspicuous duets, and more private forms of duet might have been overlooked. We investigated private vocal communication between mates in wild zebra finches, Taeniopygia guttata, a gregarious Australian songbird that forms life-long pair bonds. The partners are inseparable unless nest building, incubating or brooding. Using microphones inside nestboxes, we monitored interactive communication between partners at the nest and its variation during different stages of breeding. After periods of separation, partners performed coordinated mutual vocal displays involving specific soft vocal elements that fulfilled all the criteria used to define duets. In addition, using playback experiments, we obtained preliminary results suggesting that these soft calls could allow mate recognition. Thus, we propose that mutual displays at the nest in zebra finches represent private vocal duets and may function to mediate pair bond maintenance.

Extra-pair paternity in the long-tailed finch Poephila acuticauda

Although the majority of passerine birds are socially monogamous, true genetic monogamy is rare, with extra-pair paternity (EPP) occurring in almost 90% of surveyed socially monogamous species. We present the first molecular data on the genetic breeding system of the long-tailed finch, Poephila acuticauda, a grass finch endemic to the tropical northern savannah of Australia. Although the species forms socially monogamous pair bonds during the breeding season, we found that extra-pair males sired 12.8% of 391 offspring, in 25.7% of 101 broods. Our findings provide only the second estimate of extra-pair paternity in the estrildid finch family.