Fig. 2 in A taxonomic and conservation re-appraisal of all the birds on the island of Nias

Fig. 2. Sonograms of typical calls of the Crested Serpent Eagle Spilornis cheela. a, b, four-note and single-note calls, respectively, of asturinus from Onolimbu (Xeno-Canto accession: XC482238, XC482239; recordist: Frank E. Rheindt); c, four-note call of malayensis from Sungai Menyala Forest Reserve, Malaysia (Xeno-Canto accession: XC89521; recordist: Frank Lambert); d, single-note call of malayensis from Petaling, Selangor, Malaysia (Xeno-Canto accession: XC447920; recordist: Ding Li Yong).