Bioacoustics of Ewartia thamna

Distribution and habitat . Ewartia thamna n. sp. is described from a single locality at the southern edge of the Top End of the Northern Territory , some 76 km east of Mataranka ( Fig. 25 ). Adults were found in low bushes and in grass in dry open shrubland on weathered sediments. Specimens have been collected in early February. The distribution of E. thamna n. sp. overlaps with E. etesia n. sp. and both species have been collected at the same site (the type locality of E. thamna n. sp. ). Calling song . The only available recordings of E. thamna n. sp. made by David Marshall and Kathy Hill (n=5) do not appear to contain a definitive simple calling song mode. Due to this limitation, only the complex calling song mode is described here. This calling song mode ( Fig. 30 ) contains a sequence of 5–12 syllables (each 0.010– 0.012 s duration) or short macrosyllables (each comprising 2 syllables, 0.021– 0.027 s duration), each separated by a gap of 0.033– 0.144 s duration. This is followed by a shorter sequence of 3–5 of the short macrosyllables separated by a shorter gap of 0.008– 0.044 s duration. The subphrase then either concludes with a gap of 0.051– 0.114 s duration or proceeds rapidly to the accentuation. The accentuation comprises a single long macrosyllable or short echeme (0.052– 0.127 s duration) followed by a gap of 0.063– 0.168 s duration. Some interruptions are apparent in a few passages of successive subphrases that do not contain the accentuation, which may indicate a potential transition to a simple calling song component. These interruptions are formed by an atypically large gap of up to 0.327 s , typically occurring after the third syllable in the initial syllable sequence of each subphrase. The calling song exhibits no apparent change in frequency spectra between song modes. In each mode the calling song typically has a highest amplitude frequency plateau between 12.0 and 19.1 kHz, with a dominant frequency between 15.7 and 16.3 kHz (mean=16, n =3; e.g. Fig. 29 C). As a consequence, the call is higher pitched than other examples in the Ewartia oldfieldi species complex. This includes E. etesia n. sp. , which has been found at the same location as E. thamna n. sp. ( Fig. 25 ), and produces a calling song with a similar temporal structure (cf. Figs 26 , 27 with Fig. 30 ).