Ls 100

Marmoset vocalizations were recorded using a linear PCM recorder (Olympus, LS-100). The marmosets were isolated in a soundproof chamber and were allowed habituation to the environment for ~1 min before each recording session. The animals were placed in a small recording cage (38 × 43 × 47 cm³) located 10 cm apart from the recorder. Furthermore, vocalizations uttered during 5-min recording sessions were obtained in 24 bits at a 96-kHz sampling frequency. The recordings were started from postnatal weeks 1–3 and were performed every week up to 20 weeks, of which the data from weeks 11–13 were analyzed. The data were analyzed by an experimenter who did not know the type of animal using the Praat software (https://www.fon.hum.uva.nl/praat, version 6.1)⁶⁵ . Each call was annotated as one of the following: ekk or cough, phee, trill, tsik, twitter, phee-trill or trill-phee, and other^{66 (link)–68 (link)}. Continuous sequences of multiple calls without a silent gap (multisyllabic calls) were considered a single bout of call. Call type entropy was calculated using the ratio of each call type r_i as −Σ_ir_i log₂r_i.

Sound recordings of natural vocalizations were obtained in previous studies for domestic Barbary dove7 (link), elegant-crested tinamou68 (link) and zebra finch69 (link). A domestic pigeon call recording was obtained from www.xeno-canto.com (catalogue nr: XC92264). We recorded the mating calls of two male ostriches at an open-range ostrich-breeding farm (Langeskov, Denmark) from April to May 2013 using a shotgun microphone (model KMR82i, Neumann, Berlin, Germany) and a 24-bit digital recorder (Olympus LS-100). Cockatiel recordings were made with the same shotgun microphone and solid-state recorder (model PMD-670, Marantz, Mahwah, NJ, USA).