Microevolution of eastern palaearctic Grey tits as indicated by their vocalizations (Parus [Poecile]: Paridae, Aves) I. Parus montanus: Contributions to the Fauna of the Far East, No. 2

Abstract

Within the Palaearctic Region, the Willow tit (Parus montanus) displays four vicariant forms of territorial song. 1. “Alpine” form (pure single-frequency whistles, Fig. 5: 1) in the Alps and adjacent mountains to the East. 2. “Lowland” or “Normal” form (frequency change from high to low within one note, Fig. 5: 2) in the other parts of NW, Central and SE Europe. 3. In populations of N and E Europe as well as of W and E Siberia every individual bird uses - so far as known - both song types; this “Siberian” form (Figs. 1, 2) includes intergrades (Fig. 3). The comparatively type-rich Siberian repertoire is found in a vast area from N and E Europe to the Amur River and Ussuriland in Siberia. 4. In song types of S Palaearctic Asia whistled notes dominate, as in the Alpine form, but the single notes contrast by marked differences in pitch (frequency jumps); this is the “Sino-Japanese” form (Altai, China, Japan, Fig. 4). These acoustically defined groups of Eurasia comprise several morphological subspecies. Subspecies groups with the same song type are closely related. We hypothesize that the Alpine and Lowland song types developed in Pleistocene refuge areas in the southern Alps and in the Balkan Peninsula, respectively, both originating from the complex Siberian song type. According to this hypothesis, both extant Central European song types lost one note type of the Siberian song type (Lowland or Alpine, respectively). In contact zones and hybrid belts of Alpine and Lowland song, the Secondary Siberian song type occurs, which combines the Lowland and Alpine types. Marked song types, which cover vast areas, also characterize the closest relatives in the Nearctic Region, the Chickadees P. atricapillus, P. carolinensis and P. sclateri (Mexico), the most southerly representative of Chickadees in America. P. carolinensis uses Sino-Japanese song, P. atricapillus a derived form with only minor frequency jumps. The Willow tit probably evolved in the E Palaearctic Region, perhaps in the area of E China, Amur/Ussuri and NE Siberia, rich in diverse local taxa at present (songarus sector; parts of montanus sector; kamtschatkensis sector, respectively, Fig. 5). The Sino-Japanese song type was also developed here. Starting from this area, montanus settled the W Palaearctic Region, where the song types were modified as follows: loss of frequency jumps of the old Sino-Japanese form, threefold geographical splitting into areas of Alpine, Lowland and Siberian song. Also starting from NE Asia, the Nearctic Region was colonized by at least two immigration waves. The first one resulted in the present P. carolinensis, which introduced Sino-Japanese song into the Nearctic Region. Considered not closely related to P. carolinensis on genetic grounds, the present P. atricapillus may represent another immigrant from E Asia with already modified Sino-Japanese song (minor frequency jumps). In the Nearctic Region, Alpine song occurs in Alaska, where it resembles much Alpine song in Siberia and the rare Alpine form in Japan. Territorial song supports the currently rejected assumption of conspecifity of palaearctic and nearctic Willow tits under the name P. atricapillus. Despite allozyme differences, P. atricapillus and P. carolinensis behave largely as a common biological species. In accordance with its peculiar song, the allopatric P. sclateri is attributed species status. Song structure in both the montanus and atricapillus / carolinenis complexes of the Holarctic Region is highly conservative and gives even better insight into evolutionary history than morphological characters.