The chiffchaff’s tret calls are short sounds rhythmically repeating in intervals between the song strophes. Phonetically, tret calls differ markedly from the elements (notes) of the basic song. Although the song of the chiffchaffs from different taxa has attracted a lot of attention from researchers, the variety of tret calls still remains unexplored. We present here the results of a comparative study of tret calls of Phylloscopus collybita collybita, P. c. abietinus, P. c. tristis, P.c. brevirostris, P. c. caucasicus, P. c. menzbieri, P. sindianus sindianus, and P.s. lorenzii. Our studies also encompass two hybridisation zones of abietinus and tristis. Within the range of most taxa, the structure of the tret calls remains very uniform. One exception was the Siberian chiffchaff (tristis), whose call structure showed significant differences between populations found in Central Siberia and North–Eastern Yakutia. In contrast, different chiffchaff taxa usually perform different tret calls, however, both European taxa (collybita and abietinus) perform acoustically very similar calls. The frequency and temporal characteristics of abietinus and tristis tret calls were found to be intermediate in the hybridisation zones between them both in the Arkhangelsk region and in the southern Urals.
Avian song, chiffchaff, geographic variations, subspecies, tret calls