Bioacoustics of Yoyetta fluviatilis

Distribution, habitat and behavior. Widespread distribution through inland Queensland, New South Wales , Victoria and South Australia in association with the Murray-Darling and Lake Eyre drainage basins ( Figure 4 ). A population also occurs near the coast at Gippsland and a single specimen has also been taken at Alice Springs in the Northern Territory. Adults often emerge in large numbers after rainfall. They typically emerge on grasses and then gradually move up the trunks of eucalypts, especially River Red Gum ( Eucalyptus camaldulensis ). Individuals, including calling males, tend to remain sedentary on the trunks and upper branches of trees, unless disturbed. Occasionally, calling males will continue calling when flying briefly between singing stations. Records span from September to January. Notes on geographical variation. Specimens from the southern part of the range (south from Gilgandra in New South Wales ) tend to exhibit darker colouration than specimens from further north. Calling song. The typical call of this species has simple repetitive phrases, each comprising a short, noncoalesced, syllable sequence followed by a macrosyllable ( Figure 8 ). The syllable sequence contains 14–32 syllables (each 5–10 ms duration, 2–4 pulses, n = 18 recordings), with a silence between 4 to 31 ms between each syllable. The sequence of syllables is followed by a period of between 20 and 150 ms of silence. This is then followed by the macrosyllable, which comprises 4 to 8 syllables (45–90 ms duration). A second period of silence then follows (250–500 ms duration), which completes each phrase. Figure 9 shows a comparison of the song structure of Y. fluviatilis across the southern Queensland portion of its geographical distribution (no recordings were available from other states). While some variation is apparent between individual recordings, the distinctive structure of the call is demonstrated to be quite consistent across this wide area (distance of over 900 km ). Anecdotal behavioural observations by LWP indicate that the macrosyllable acts as a cue for female response; however, this behaviour has not yet been captured in any recordings. The female wing flick response is expected to occur during the second period of silence at the end of each phrase. Occasionally males produce an anomalous variation of the typical call in which the macrosyllable is not produced. In these instances the silence following each short rattle is approximately 250 ms in duration. The phrase duration in the typical call ranges from 650 to 1475 ms. The typical repetition rate of syllables in the short rattle ranges from 25.0 to 111.1 Hz. The frequency spectrum of the calling song ranges between 5.5 and 17 kHz, with highest energy between 10 and 16 kHz, and a dominant frequency of approximately 13 kHz ( Figure 8 ).