Myioborus melanocephalus ruficoronatus (Kaup, 1852)

Cuervo, Andrés M. & Céspedes Arias, Laura N., 2023, The type of Setophaga ruficoronata (Kaup 1851) is a hybrid: implications for the taxonomy of Myioborus warblers (Passeriformes: Parulidae), Zootaxa 5383 (4), pp. 476-490 : 477-479

Myioborus melanocephalus ruficoronatus is not a valid taxon

The northern subspecies of M. melanocephalus was described as Setophaga ruficoronata Kaup, 1851 based on a single specimen collected by Adolphe De Lattre ( Kaup 1851). The holotype is housed at the Vertebrate Zoology Collection, World Museum, National Museums Liverpool (formerly known as Museum of the Earl of Derby, Museum Derbyanum or Derby Museum), accession number NML-VZ D193. We examined photographs and an illustration of the type as it appeared in Salvin’s (1878) monograph on Myioboru s and other warblers grouped back then in the genus Setophaga . The color and pattern combination in the head and face of the type (see Kaup 1851; Bonaparte 1854; Baird 1874; Salvin 1878; Sharpe 1885) agrees with individuals of the center of the hybrid zone around Pasto, Department of Nariño, Colombia ( Céspedes-Arias et al. 2021). Specifically, the type exhibits yellow lores and forehead (like the northern parental taxon: M. o. chrysops ) a subtle black malar line, black auriculars, and a chestnut center of crown (like the southern parental taxon in central Ecuador). Assuming a complete lack of white auricular feathers, which cannot be confirmed from photographs, the hybrid score corresponding to this specimen is 0.59, lying near the middle in a scale ranging from 0 (phenotypically M. o. chrysops ) to 1.0 (phenotypically Ecuadorian M. melanocephalus ) (following methods and baseline data from Céspedes-Arias et al. 2021). Although the type of S. ruficoronata Kaup, 1851 agrees with specimens from central Nariño and the Sibundoy Valley (Department of Putumayo, Colombia), the presumed type locality is uncertain.

From the original label of the S. ruficoronata type ( Fig. 2 ) and its description ( Kaup, 1851), Leadbeater presented the De Lattre specimen in December 1846, but no specific locality was given ( Bonaparte 1854). However, a small label attached to the type reads “Caly.” By the time Salvin (1878) revised the group, an additional label in the type stated “Cali, Colombia ” as the collecting locality, but this was most likely an error induced by the interpretation of the small “Caly” label. First, Kaup (1851) did not indicate explicitly Cali or any locality whatsoever as the origin of the type ( Bonaparte 1854). Ever since Salvin (1878), it has been assumed that De Lattre obtained the specimen at Cali ( Chapman 1926; Zimmer 1949). Second, Cali lies at the bottom of the upper Cauca valley at 1000 m elevation, where no Myioborus warblers occur ( Fig. 1 ). If De Lattre had collected Myioborus in the mountains surrounding Cali, as was formerly suspected ( Chapman 1926; Hellmayr 1935), these would have corresponded to M. miniatus at low or M. o. chrysops at high elevations. Moreover, Salvin (1878) noticed that an additional specimen of M. o. chrysops taken by De Lattre at “Páramo of Popayán” (most likely in Puracé, Department of Cauca) in the Central Cordillera, ~ 110 km south of Cali, “agrees very closely with Mr. Salmon’s examples” of M. o. chrysops from Department of Antioquia, also in the Central Cordillera. Although hybrid zones can move ( Taylor et al. 2015; Aguillon & Rohwer 2022), that hybrids could have been observed as far north as Cali (3.5º N latitude) 180 years ago seem unlikely because the current approximate hybrid zone northern limit, as inferred from plumage variation, is located 200 km to the south (1.7º N latitude) in southern Cauca ( Céspedes-Arias et al. 2021).

In addition to Cali, De Lattre collected birds in various other locations of southwestern Colombia ( De Lattre & Bourcier 1846; Hellmayr 1911; Chapman 1917), including the Pacific lowlands (Buenaventura), the western (Juntas) and central cordilleras (Puracé, Popayán), and the southern Colombian Andes (Pasto). Hybrid individuals with an external appearance that closely resembles the S. ruficoronata type can be found near Pasto and surrounding areas ( Céspedes-Arias et al. 2021). Because De Lattre took a fair number of specimens from Pasto ( De Lattre & Bourcier 1846), it is possible that this corresponds to the real locality of collection of the S. ruficoronata type specimen.

Because the name-bearing type is a hybrid individual, the name ruficoronatus Kaup, 1951 (currently applied to a subspecies of M. melanocephalus ) is here rendered unavailable for the southern parental Myioborus population of the hybrid zone ranging in the Ecuadorian Andes. This type does not anchor any taxon at the species or subspecies level. In consequence, a name should be created or reinstated for the parental taxon south of the hybrid zone.

Figures

FIGURE 1. Map of northwestern South America showing the geographic distribution of high-elevation Myioborus warblers of the Northern Andes (M. albifrons, M. ornatus and M. melanocephalus). Each colored polygon represents the approximate geographic distribution of taxa recognized in this study, except for the one in dark gray, which shows the extent of the hybrid zone (Céspedes-Arias et al. 2021) between chrysops and bairdi. Gray dots indicate type localities of valid taxa, and the star the location of Cali, Colombia, the supposed type locality of M. m. ruficoronatus, which is most likely an error (see text). The question mark indicates the uncertainty in the geographic limits between bairdi and griseonuchus in southern Ecuador.

FIGURE 2. Photographs of the type specimen of Setophaga ruficoronata Kaup, 1851 (NML-VZ D1931) currently treated as Myioborus melanocephalus ruficoronatus. Side and dorsal views, with the detail of the front and face, and its label. The type exhibits intermediate facial color and pattern as observed in the center of the hybrid zone near Pasto, Department of Nariño, southern Colombia (Céspedes-Arias et al. 2021). Photographs by Tony Parker and John James Wilson (World Museum, National Museums Liverpool).