ИСТИНА

Birds without vocal learning exhibit different styles of vocal development. For some Anseriformes, Galliformes and Charadrii species gradual changes of call-frequency variables throughout development have been reported, while for some Gruiformes, Procellariiformes and Coraciiformes species the changes are jump-like. Distribution of the vocal development types among other bird taxa, however, is poorly known. We analysed early vocal development in three auk species (Alcidae): Crested Auklet Aethia cristatella, Tufted Puffin Fratercula cirrhata and Horned Puffin F. corniculata. All three species have semi-precocial chicks that stay in nest-burrows until fledging. We recorded calls from 26–35 chicks of each species at four–five ages between hatching and fledgling and from six fledglings of Crested Auklet at a breeding colony on Talan Island, Sea of Okhotsk. We compared main temporal-frequency variables of chick calls across ages and with common adult calls. In all species we observed the lack of a gradual change in the fundamental frequency of calls between hatching and fledging despite a considerable increase in body size. Fundamental frequency actually increased slightly over development and was always higher then that of adult calls. Interestingly, calls of two Tufted Puffin chicks just before fledging and five Crested Auklet fledglings contained two non-overlapping independent fundamental frequencies in the spectrum. The upper frequency band didn’t differ in values from juvenile fundamental frequency band, and the lower frequency band didn’t differ from fundamental frequency measured in adult calls. Such two-frequency calls have also been reported previously for some other non-passerines and their appearance used as a marker of start of voice-breaking. Thus, we confirm the presence of jump-like vocal development through the stage of voice-breaking in Alcidae and speculate that such patterns of vocal development could be widespread among bird species across the altricial spectrum.