The genus Micrastur (forest falcons) is currently considered to comprise seven species spread across the Neotropical realm and divided into two clades: the Collared Forest Falcon M. semitorquatus clade, which also includes Slaty-backed Forest Falcon M. mirandollei and Buckley's Forest Falcon M. buckleyi; and the Barred Forest Falcon M. ruficollis clade, which also includes Lined Forest Falcon M. gilvicollis, Plumbeous Forest Falcon M. plumbeus and Cryptic Forest Falcon M. mintoni (Fuchs et al. 2011, Soares et al. 2019). The M. ruficollis clade, which includes cryptic species only recently recognised (see Schwartz 1972, Whittaker 2003¹), split into its constituent lineages only recently (c.2.5 MYA), and sufficiently rapidly that the divergence pattern among species cannot be fully resolved (Fuchs et al. 2011). Within this clade, the range of M. ruficollis encompasses that of the three other members. Because of overall plumage variation, an array of available species-group names was conferred historically, some of which have been overlooked more recently, therefore potentially challenging the application of recently proposed names.

M. mintoni is the most recently named species, occurring in both Amazon and Atlantic rainforests, without any noticeable difference in plumage or voice between the two allopatric populations (Whittaker 2003, Simon & Magnago 2013). Such a geographic range overlaps with that originally attributed to M. guerrilla jugularis Gurney, 1884, based on grey-backed birds (see details below). However, Gurney's name was not evaluated in the description of M. mintoni Whittaker, which is also a grey-backed taxon, so there remains the possibility that jugularis is conspecific with, and would have priority over, mintoni. For this reason, here we review the composition of the type series and the application of the name M. guerrilla jugularis in the context of all recent advances in the taxonomy and systematics of the genus Micrastur.

The name Micrastur guerilla jugularis was conferred by Gurney Sr. (1884: Appendix B) on six specimens, which he considered to be grey-backed adults intermediate in overall appearance between M. guerilla and M. ruficollis, notably as regards ‘… having the jugulum [lower throat area] suffused with rufescent buff, extending over the transverse dark and pale bars…’ (Gurney 1884: 117); hence his subspecies name, jugularis. Four of these specimens were in the Norwich Museum collection and two in that assembled by Salvin and Godman, and they ranged geographically from Bahia (eastern Brazil) to Venezuela and Colombia (with one specimen labelled simply ‘South America’); details provided for each by Gurney are given in Table 1 (columns A–C). Since no formal designation of a holotype was made, all six specimens are deemed syntypes (ICZN 1999, Art. 73.2). All would now be expected to be in the Natural History Museum, Tring (NHMUK), in which Salvin and Godman’s bird collection and the raptor collection of Norwich Museum were subsequently deposited (Sharpe 1906; pers. obs.).

TABLE 1

Data associated with syntypes of the name Micrastur guerilla jugularis Gurney, 1884. Columns A–C = data provided in Gurney (1884). Columns D–F = additional information from specimen labels, the relevant catalogue (Gurney 1889, now held by NHMUK) and/or NHMUK register. See text for further discussion of uncertainties indicated.

Prior to the formal description by Gurney, the two specimens from Bahia had previously been examined and discussed (fide Gurney 1884: 118) by Sclater & Salvin (1869) and Ridgway (1875), who respectively considered them to represent near-adult and adult ‘plumbeous phase’ specimens of what is now Micrastur ruficollis. Following Gurney’s description, the status of jugularis was considered by Sclater (1918), Hellmayr (1921, 1929) and Hellmayr & Conover (1949), who all synonymised it within M. ruficollis, in some cases highlighting that more than one of the latter’s subspecies must be involved. Swann (1922, 1925) ‘restricted’ the type locality of jugularis to ‘Venezuela’, but that statement is in disagreement with Art. 73.2.3 of the International code of zoological nomenclature and is thus invalid (ICZN 1999: ‘… if the syntypes originated from two or more localities (including different strata), the type locality encompasses all of the places of origin’). His restriction does not qualify as a lectotype designation either (ICZN 1999, Art. 74.5), as he did not use the term ‘lectotype’ or an equivalent expression, nor did he explicitly select a specimen to serve as name-bearing type (in fact, he did not mention any specimen at all). However, none of these authors seems to have examined first-hand the four Norwich Museum specimens of the jugularis type series and, subsequent to Hellmayr & Conover (1949), the name jugularis does not appear to have been mentioned again in the literature.

Aware of Gurney's name, VQP located five of the six syntypes on a visit to NHMUK. These specimens were among the main collection, having unsurprisingly (given the obscure history of jugularis) not been mentioned by Warren (1966) nor, in consequence, been segregated. Registration and other relevant label details regarding these specimens are given in Table 1, alongside the data provided by Gurney (1884).

A number of points in Table 1 require clarification. Although specimen no. 2 has labels clearly showing it was collected by Otto Wucherer (1820–73), a Brazilian doctor and naturalist who lived in Bahia (now Salvador), specimen no. 1 does not. Instead, the earliest of its three labels, a piece of card, has merely the name Jamrach scrawled on it, although the relevant NHMUK register (dating from receipt there of Salvin and Godman's specimens in 1887) ascribes both to Wucherer. As Charles Jamrach (1815–91) was not himself a collector, but instead a well-known London wildlife dealer, specimen no. 1 may well have been collected by Wucherer but obtained by Salvin via Jamrach. Salvin sent his entire holdings of Micrastur specimens to Robert Ridgway at the United States National Museum (USNM), Washington, DC, for examination, and Ridgway specifically mentioned two Salvin ‘plumbeous phase’ adult ruficollis specimens from Bahia that he saw (Ridgway 1875: 494); both nos 1 and 2 now have USNM labels with comments by Ridgway reflecting this. Both specimens also have subsequent label annotations by Charles E. Hellmayr, stating ‘One of the types of M. jugularis Gurney’.

Figure 1.

From top to bottom: dorsal, lateral and ventral views of specimen NHMUK 1887.5.1.136, from Bahia, Brazil, collected by Otto Wucherer, here designated as the lectotype of Micrastur guerilla jugularis Gurney Sr., 1884 (Vítor Q. Piacentini, © Trustees of the Natural History Museum, London)

Specimen no. 6 has neither any locality beyond ‘South America’ nor any indication of who collected it, Warwick being merely a London specimen dealer active in the mid-1800s (Griffiths 1996a,b) from whom NHMUK obtained it. However, it is Gurney’s (1884) specimen no. 5 from ‘Brazil’ that causes most problems in matching to an extant skin. Gurney’s unpublished catalogue of raptors then in the Norwich Museum, compiled by the museum curator, James Reeve, lists six specimens under the name Micrastur jugularis (Gurney 1889: 456), of which three adults are unambiguously nos. 3, 4 and 6 of Gurney (1884). The three other specimens, from ‘Eastern Ecuador’, ‘South America’ and ‘Bahia’ are listed as immatures; all are now in the NHMUK collection and are clearly young birds with a plumage very distinct from that described by Gurney (1884) for his syntype adults. Furthermore, none is labelled as coming from ‘Brazil’.

All potentially relevant Gurney (1889) specimens, adult and juvenile, within the wider ruficollis clade that are listed as being from ‘Brazil’ can now be accounted for in the NHMUK collection; furthermore, there appear to be no candidate specimens left in the Norwich Museum nor any potentially relevant specimen disposed of from there between 1884 and 1889 (T. Irwin in litt. 2011). Among NHMUK material, only a single additional ‘Brazil’ bird in the wider ruficollis clade reasonably matches the plumage criteria of Gurney (1884) for jugularis, displayed by the five definite syntypes. This is NHMUK 1955.6.N.3354, listed as a ‘nearly adult’ M. ruficollis and received by Gurney from H. Whitely. Henry Whitely Sr. was a 19th-century London dealer, whose specimens frequently have rather general localities (Rasmussen & Prŷs-Jones 2003), and his son, Henry Whitely Jr., collected birds in several South American countries (Anon. 1893). Overall, it therefore seems possible, though not provable, that specimen NHMUK 1955.6.N.3354 may be the sixth jugularis syntype, though why its Gurney label and the Gurney (1889) catalogue should not reflect this is unclear.

Both the localities and plumages (e.g. tail-bands, rufous tones) of the definite syntype specimens in Table 1 support the view that the jugularis type series is a composite, with the syntypes apparently representing more than one taxon within the current, widely accepted taxonomy of the Micrastur ruficollis complex, namely M. r. concentricus/zonothorax (Colombia and Venezuela), and nominate M. r. ruficollis (Bahia, Brazil) (Fuchs et al. 2011, del Hoyo & Collar 2014, Soares et al. 2019). Hellmayr & Conover (1949) previously highlighted the potential multiple identities of Micrastur guerilla jugularis, but nonetheless made no explicit lectotype designation. Thus, following the International code of zoological nomenclature (ICZN 1999, Arts. 74.1 and 74.7, including amendments), here we formally designate specimen NHMUK 1887.5.1.136, from Bahia, collected by Otto Wucherer (Fig. 1), as the lectotype of Micrastur guerilla jugularis Gurney, 1884, which then becomes a subjective synonym of M. r. ruficollis (Vieillot, 1817). Our designation further adheres to the Code regarding the selection of a syntype from a known locality (Recommendation 74E).