Bioacoustics of Yoyetta corbinorum

Distribution, habitat and seasonality. ( Plate 8E–F ; Fig. 1 ). This species is often the first to emerge in eastern Melbourne, usually around late September or early October and can persist until late January. It favours the upper branches of Eucalyptus regnans (Mountain Ash) at altitudes> 600m , and specimens are currently restricted to the Dandenong and Yarra ranges east of Melbourne. Since males appear to call constantly at rest from great heights, Y. corbinorum sp. nov. have only been captured emerging around 2100h on shrubs, ferns and grasses close to stands of Mountain Ash. However, they are readily attracted to light, appearing in large numbers at Wirrawilla Reserve in late December 2022 .

Calling song ( Fig. 10 ). The male calling song of Y. corbinorum sp. nov. is a series of repetitive chirps. Further examination of the calling song (all statistics, n =5 from the Dandenong Ranges) in Fig. 10 illustrates a ‘chirp’ is a macrosyllable ranging from 0.029 to 0.050 s duration, with a gap between each macrosyllable ranging from 0.214 to 0.245 s duration. The frequency plateau ranges between 8.1 and 14.3 kHz, with a dominant frequency between 9.3 and 10.9 kHz ( Fig. 10C ). Males call from around 0800h and appear to remain at rest for periods approaching 15-30min. Males will still call under cloud cover, even when temperatures fall to around 15C. Female wing flicking has not been detected except in captivity (approximately 0.05 s after a male chirp), and is likely due to their elevated locations in the treetops. Finger snapping to attract males has been successful only on limited occasions, again likely to the height of their preferred locations. The male calling song of Yoyetta corbinorum sp. nov. most closely resembles those of Y. robertsonae and Y. robusta Popple & Emery and Y. repetens Emery, Emery & Popple. While Y. robertsonae shares an overlapping distribution with Y. corbinorum sp. nov. , its call consists of a series of three ticks, whereas Y. corbinorum sp. nov. produces a single macrosyllable. This strident chirping is similar to that of Y. robusta but occurs at a higher frequency (>9.3kHz for Y. corbinorum sp. nov. and around 8.3 kHz for Y. robusta ), and their distributions do not overlap. Additionally, Y. corbinorum sp. nov. is not known to exhibit call variation when at rest, unlike Y. robusta . When compared with Y. repetens , the macrosyllables of Y. corbinorum sp. nov. are shorter (29–50ms duration) compared with the former and their locations do not overlap.