Geographical Variability of Morphological and Acoustic Signs of the North Populations of the Long Tailed Tit Aegithalos caudatus (Passeriformes, Aegithalidae)

Abstract

The geographic variability of the morphological and bioacoustic characteristics of the long-tailed bushtit, or long-tailed tit (Aegithalos caudatus), was studied, and the validity of the selection of the controversial subspecies Ae c. japonicus Prazak 1897 was evaluated., Ae. c. brachyurus Portenko 1954 and Ae. c. sibiricus (Seebohm 1890), distributed from Scandinavia and Eastern Europe to the Pacific coast. On the basis of a study of nine metric characters and three signs of coloration, we showed that in the space of the range of white-head long-tailed tits from Eastern Europe and Scandinavia to Primorye and Sakhalin, the majority of morphological characters slightly fluctuate or change in a clinal mode; i.e., they change gradually. The vocalization of the nominative subspecies of long-tailed tits is analyzed for the first time. When comparing samples from neighboring regions, no significant differences were revealed, either morphologically and acoustically, so the names Ae. c. sibiricus and Ae. c. brachyurus should be synonymous with the nominative subspecies Ae. c. caudatus. Only the populations of long-tailed tits of the southern Kuril Islands and Hokkaido Islands can be isolated as an independent subspecies Ae. c. japonicus.