Bush robins are members of the genus Tarsiger, a group of small, colorful birds with high species richness in the Sino-Himalayan region.
The Qilian bluetail (Tarsiger albocoeruleus). Image credit: Xianting Wang.
“Bush robins are small (12-15 cm in body length), insectivorous and sexually dimorphic songbirds with distinctive male plumage and songs,” said Uppsala University’s Dr. Per Alström, Sun Yat-sen University’s Dr. Liu Yang and their colleagues from China, the United States and Europe.
“These birds breed from lowland temperate-zone forests near sea level (Tarsiger cyanurus) to high-elevation forests and alpine scrub up to 4,600 m (Tarsiger chrysaeus), with the subtropical taxa being montane.”
“Most species in the Sino-Himalayan region and Taiwan are elevational migrants with range shifts from high altitude to mid-elevation or foothills during the non-breeding season.”
“The only long-distance migrant in the genus, Tarsiger cyanurus, breeds from Finland to eastern Asia and migrates to southwest and south China and adjacent parts of Southeast Asia in the non-breeding season, although the population in Japan also undertakes altitudinal migration.”
“With six currently recognized species in the Sino-Himalayan region, Eurasian Arctic, and the island of Taiwan, the Tarsiger bush robins comprise an ideal group for the study of biogeographical patterns of diversification and speciation.”
The Taiwan bush robin (Tarsiger formosanus). Image credit: Vincent Wang.
In the new study, Dr. Alström, Dr. Yang and co-authors investigated species limits in the Tarsiger genus.
The ornithologists collected and analyzed DNA and acoustic samples from all 11 subspecies of the six currently recognized species.
“In the present study, we carried out an integrative taxonomic study of the Tarsiger bush robins based on mitochondrial and nuclear DNA markers, using both phylogenetic methods and coalescent-based species delimitation, and analyses of plumage, morphometrics and bioacoustics,” they explained.
Their results suggest recognition of two overlooked species: Tarsiger albocoeruleus and Tarsiger formosanus.
“Our results reveal that the isolated north-central Chinese populations of Tarsiger cyanurus, described as the subspecies Tarsiger cyanurus albocoeruleus but usually considered invalid, is distinctive in genetics and vocalization, but only marginally differentiated in morphology,” they said.
“We also found the Taiwan endemic Tarsiger indicus formosanus to be distinctive in genetics, song and morphology from Tarsiger indicus indicus and Tarsiger indicus yunnanensis of the Sino-Himalayan mountains.”
“We suggest recognition of the Taiwan endemic as an independent species, Tarsiger formosanus, for which we propose the English name ‘Taiwan bush robin,’ reflecting its endemic island distribution.”
“We also suggest treatment of Tarsiger cyanurus albocoeruleus as a distinct species, Tarsiger albocoeruleus, with the tentative English name ‘Qilian bluetail,’ reflecting its core breeding range in the Qilian Mountains.”
“It is unknown whether this species is resident or migratory, however given the mid-winter climate of the breeding grounds it seems likely that it at least an altitudinal migrant. Identification away from the breeding range would likely require molecular analysis.”
The study was published in the October 2022 issue of the journal Molecular Phylogenetics and Evolution.
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Chentao Wei et al. 2022. Cryptic species in a colorful genus: Integrative taxonomy of the bush robins (Aves, Muscicapidae, Tarsiger) suggests two overlooked species. Molecular Phylogenetics and Evolution 175: 107580; doi: 10.1016/j.ympev.2022.107580
