Collared Bush Robin Tarsiger johnstoniae is endemic to the island of Taiwan and its male is arguably the most phenotypically distinctive member of its genus (Clement & Rose 2015). It is one of two bush robins that are resident on Taiwan, the other being White-browed Bush Robin T. indicus, which is represented by an endemic subspecies, formosanus, described by Collar (2005) as ‘moderately distinctive’ in plumage, but which a recent molecular phylogeny suggested was sufficiently different genetically to warrant treating at species rank (Wei et al. 2022); T. i. formosanus is also quite geographically disjunct. A third species, Red-flanked Bluetail T. cyanurus, is a non-breeding visitor to the island.

T. johnstoniae was described by Ogilvie-Grant (1906) from two specimens (syntypes), a male and female, collected in early 1906 by the professional zoological collector Walter Goodfellow (1866–1953) and now held at the Natural History Museum, Tring (NHMUK; Warren & Harrison 1971). T. i. formosanus was described by Hartert (1910) from specimens of both sexes (the male holotype and single male and female paratypes) collected on Mount Arizan, also in central Taiwan, and now held in the American Museum of Natural History, New York (LeCroy 2005). In particular, Hartert (1910) carefully distinguished how the female of his new taxon differed from the same sex of T. johnstoniae. Despite this, just two years later, Ogilvie-Grant (1912) described a third taxon, Ianthia goodfellowi, from the same locality, Mount Arizan. It too was based on single male and female specimens obtained by Goodfellow and now held at NHMUK (Warren & Harrison 1971). Perhaps unsurprisingly, I. goodfellowi very quickly fell into the synonymy of T. i. formosanus; it is not even mentioned in the relevant volume of the Peters checklist (Ripley 1964).

In the original description of Ianthia johnstoniae¹, Ogilvie-Grant (1906) reported that he had both a male and female, provided descriptions and measurements of both, and stated that Mt. Morrison is the new species' ‘habitat’ (= type locality). Finally, he mentioned that he was naming the new species ‘in honour of Mrs. Johnstone’, i.e., Marian Ada Johnstone (1870–1954), an English aviculturist (Jobling 2010). In a subsequent paper, published one year later, Ogilvie-Grant and La Touche (1907) noted that the ‘types of the species’ were collected in the Racu Racu Mts. (the male) and on Mt. Morrison (the female), in February and January 1906, respectively, both at 8,000 ft. Chang & Severinghaus (1979) clarified that the first-named locality probably corresponds to the range between Tung Pu Hot Springs and Patungkuan in Nantou County. Under the Code (ICZN 1999), Art. 73.2.3 states that ‘if the syntypes originated from two or more localities...the type locality encompasses all of the places of origin.’

In September 2023, as part of a planned revision of the Collared Bush Robin account for Birds of the world (Kirwan et al. 2024), GMK searched for the female syntype of Ogilvie-Grant's nomen Ianthia johnstoniae. It (NHMUK 1907.12.12.40, sequential with the male syntype, which is NHMUK 1907.12.12.39) was eventually located among the specimens of T. i. formosanus, one of its labels having been modified to read ‘Ianthia goodfellowi’ (Fig. 1). Rather remarkably, the female syntype of I. goodfellowi had at some time in the past been discovered among the tray of T. johnstoniae, where it had been correctly identified as Ogilvie-Grant’s other syntype; this specimen is NHMUK 1913.1.29.52 (i.e. sequential with the male syntype of I. goodfellowi, NHMUK 1913.1.29.51, which was listed by Warren & Harrison 1971). In both cases, the accompanying label data further satisfactorily identified these female specimens as the relevant syntypes of Ianthia johnstoniae and I. goodfellowi, respectively.

Separating females of the two Tarsiger species on Taiwan can be difficult (e.g., Brazil 2009, Clement & Rose 2015, Hsiao & Li 2017, Kirwan et al. 2024). As emphasised by several of these works, and indeed Hartert (1910) when he described formosanus, the single most reliable feature is the colour of the undertail-coverts: white or principally whitish in T. johnstoniae and yellowish buff in T. i. formosanus. Based on this, it seems clear that both the female syntype of Ianthia goodfellowi Ogilvie-Grant, 1912, and the female syntype of Ianthia johnstoniae, Ogilvie-Grant, 1906, are representatives of the same taxon, namely that now known as T. i. formosanus (see Fig. 2). It is conceivably odd that Hartert (1910) did not notice this, although certainly not as strange as Ogilvie-Grant (1912) so swiftly publishing a straight synonym of Hartert's name. Published mensural data (Clement & Rose 2015, Severinghaus et al. 2017) do not suggest that biometrics can be used to help identify a single individual. Although it has been claimed that the two Taiwanese Tarsiger species occasionally hybridise (Severinghaus & Severinghaus 1984, Severinghaus et al. 2017), which might potentially make females even harder to identify, to date assumed hybrids have been individuals exhibiting only rudimentary male features, including a black throat, black cheeks, and a few rusty feathers on the scapulars Kirwan et al. 2024). According to Kirwan et al. (2024), ringing data have revealed such individuals to be not rare and all are female, meaning that they are presumably older females that have acquired male characteristics, rather than hybrids.

Figure 1.

Female syntype of Collared Bush Robin Tarsiger johnstoniae, collected by Walter Goodfellow at 8,000 ft. [c.2,440 m] on Mt. Morrison, Taiwan, in January 1906, and held in the Natural History Museum, Tring (NHMUK 1907.12.12.40); herein reidentified as a female White-browed Bush Robin T. indicus formosanus (Jonathan Jackson, © Trustees of the Natural History Museum, London)

Figure 2.

Female syntypes of Ianthia goodfellowi (a synonym of White-browed Bush Robin T. indicus formosanus) (NHMUK 1913.1.29.52; left; for collection details, see main text) and Collared Bush Robin Tarsiger johnstoniae (NHMUK 1907.12.12.40; for collection details, see Fig. 1), showing their identically coloured undertail-coverts (Guy M. Kirwan, © Trustees of the Natural History Museum, London)

That the original series of Ianthia johnstoniae is mixed becomes less surprising when one recalls that the two syntypes were collected an unknown number of weeks apart and at quite different localities (Ogilvie-Grant & La Touche 1907). Furthermore, in recounting the ‘discovery’ of Ianthia goodfellowi, Ogilvie-Grant (1912) reported that Goodfellow had found the two species of bush robins syntopically and had initially thought that the white-browed males were young males of johnstoniae, whereas in reality they were just representatives of Hartert’s recently described taxon, formosanus.

Figure 3.

Male lectotype of Collared Bush Robin Tarsiger johnstoniae, collected by Walter Goodfellow at 8,000 ft. [c.2,440 m] in the Racu Racu Mts., Taiwan, in February 1906, and held in the Natural History Museum, Tring (NHMUK 1907.12.12.39) (Jonathan Jackson, © Trustees of the Natural History Museum, London)

Warren & Harrison (1971: 276) identified the two syntypes of Ianthia johnstoniae listed by Ogilvie-Grant & La Touche (1907), and provided details of the adult male collected by Walter Goodfellow at 8,000 ft. [c.2,440 m] in the Racu Racu Mts. in February 1906 (NHMUK 1907.12.12.39). It was subsequently placed in one of the type collection cabinets at Tring, and given a red ‘Type’ label. Because it was not formally designated as a lectotype (Warren & Harrison specifically mentioned that ‘the female syntype is also in the collection’), the adult male maintained the same nomenclatural status as the other syntype of I. johnstoniae (Arts. 72.4.7 and 74.5; ICZN 1964, 1999). In light of the revelation that the syntypes represent two different species and in order to fix the identity on the universally understood taxonomic concept associated with Tarsiger johnstoniae, we select as its lectotype the unambiguously identified male specimen (NHMUK 1907.12.12.39; Fig. 3) collected in the Racu Racu Mts. and listed by Warren & Harrison (1971). This designation satisfies Arts. 74.7.1, 74.7.2 and 74.7.3 (both original and amended versions; ICZN 1999, 2003), as well as being in accord with Recommendations 74A and 74C. It results in NHMUK 1907.12.12.40 becoming a paralectotype of I. johnstoniae, irrespective of its taxonomic identity. This designation fixes the identity of I. johnstoniae and maintains stability of this nomen, thereby fulfilling a primary objective of the International Commission on Zoological Nomenclature to promote stability of scientific names (ICZN 1999). In contrast, selecting the female (NHMUK 1907.12.12.40) as the lectotype would be exceptionally and needlessly disruptive nomenclaturally as the taxon currently known as T. i. formosanus would become T. johnstoniae, while the current species johnstoniae would require a new name.