The misidentification of Turdus ustulatus Nuttall, and the names of the nightingale-thrushes (Turdidae: Catharus)

Abstract

An extensive review of Turdus ustulatus Nuttall, 1840, and T. swainsoni Cabanis in Tschudi, 1845, and comparison of John K. Townsend's extant study skins (1835-36) to freshly prepared skins of Catharus ustulatus (Nuttall), C. swainsoni (Cabanis) and C. guttatus (Pallas, 1811), reveals that the original description of T. ustulatus Nuttall, 1840, was most likely based on a single specimen (now lost) of Hermit Thrush C. guttatus (Pallas, 1811). The original description of T. swainsoni Cabanis in Tschudi, 1845, is also not unambiguously identifiable and the type material is untraceable. To resolve and stabilise nomenclature, (1) a petition will be filed with the International Commission of Zoological Nomenclature (ICZN) to set aside Art. 75.3.5 of the Code (ICZN 1999) so that a neotype of T. ustulatus Nuttall, 1840, can be designated; and (2) the name C. swainsoni (Cabanis in Tschudi, 1845) is herein rescued via neotypification. Finally, updated common names are proposed to standardise the English group name of the genus to 'nightingale-thrush' and reduce further confusion with respect to common names that have been applied to multiple taxa. This is the second in a series of papers concerning historical aspects of Catharus taxonomy and nomenclature.

Neotypification of Catharus ustulatus (Nuttall)

“…Neither study skin promoted as 'the only specimen' of T. ustulatus described by Nuttall ( 1840 (Halley 2019). T. ustulatus was based on two syntypes: (1) a female collected on the '10th of June' (1834 or 1835) that was the subject of Nuttall's (1840: 401) morphological diagnosis, and (2) a female collected on 'the 19th June [1835]' that was mentioned in a note by Audubon (1839: 203-204) and cited among the synonyms of T. ustulatus by Nuttall (1840: 400, 'in a note').…”

“…In a recent paper, I scrutinised the original description of T. ustulatus Nuttall, 1840, which was based on two specimens in this collection (Halley 2019). I reviewed non-print primary sources and the published literature, and prepared a series of fresh study skins of both Catharus species from coastal Washington-C. guttatus (Pallas, 1811) and C. ustulatus (Nuttall, 1840)-and directly compared them to two of Townsend's extant skins at ANSP.…”

“…I reviewed non-print primary sources and the published literature, and prepared a series of fresh study skins of both Catharus species from coastal Washington-C. guttatus (Pallas, 1811) and C. ustulatus (Nuttall, 1840)-and directly compared them to two of Townsend's extant skins at ANSP. I published compelling evidence that Nuttall's (1840: 401) original description of T. ustulatus was based on a specimen of C. guttatus, a different species to prevailing usage (Halley 2019).…”

“…Two extant C. guttatus specimens from Townsend's collection-MCZ 16298 and ANSP 16091-can also be eliminated as potential types for the same reason: original data that conflict with Nuttall's (1840) and Audubon's (1839) accounts (Halley 2019: 248) The name Catharus ustulatus (Nuttall) has been in use for more than 180 years, referring to the 'russet-backed' taxon that breeds in coastal forests of western North America and migrates along the Pacific coast to non-breeding grounds in Middle America. The nomenclatural instability exposed by Halley (2019) requires nomenclatural action to resolve, irrespective of whether C. ustulatus and its sister taxon C. swainsoni (Cabanis in Tschudi, 1845), which has a transcontinental breeding distribution in the boreal zone of North America and migrates to non-breeding grounds in Central and South America, are classified as species (e.g., del Hoyo & Collar 2016, Halley 2019) or subspecies (e.g., Chesser et al 2018).…”

Natural selection and circular pathways to seasonal migration in birds

“…Color scheme is standardized across figures. (33) and (36) with taxonomic updates by (38). Color scheme is standardized across figures.…”