Systematics

No reported geographic variation in morphometrics; seven subspecies usually recognized, based on variation in plumage:

Catharus f. fuscater Lafresnaye

Type Specimen.—Holotype is #76525 at the Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts

Diagnoses.—Lafresnaye (1845) wrote [sic], "M. fuscater — Myiot. supra capitisque lateribus totus fuscater, pileo nigro; subtus griseus, gutture medioque abdomine albicantibus; rostra pedibusque flavis, maxilla fusca. Longit. tota 15 cent. Habit. ad Bogotam." (translation: "[Myioturdus] on the sides of the head completely dark, black cap, gray underneath, throat and mid abdomen whitish, yellow beak and feet, dark cheek. Total length 15 cent. Collected from Bogota."). Hellmayr (1932): "Three adults from Merida (Culata) agree in every respect with a series from Santander and "Bogota" skins. Birds from Ecuador are nowise different..."

Catharus f. caniceps Chapman

Type Specimen.—Holotype is #175530 at the American Museum of Natural History (AMNH), New York, NY.; an adult male collected by H. Watkins on 16 September, 1922, in Palambla, Peru. Five paratypes accompany the holotype (AMNH, 175531—17535).

Diagnoses.—Chapman (1924) justified the establishment of a new taxon based on two plumage attributes: (1) "crown grayer", and (2) "breast paler". Hellmayr (1934) found caniceps to be "very close to C. f. fuscater, but not so blackish above, the pileum nearly concolorous with the back; ivory abdominal area more extensive; the chest but slightly tinged with grayish. We have not seen any birds from central Peru, but from Taczanowski's remarks on a specimen from Chilpes (Junin) it would appear that they are referable to the present form rather than C. f. mentalis."

Catharus f. hellmayri Berlepsch

Type Specimen.—Holotype is at Naturmuseum Senckenberg, Frankfurt, Germany, specimen # ?. Collected in Veragua, Costa Rica.

Diagnoses.—Berlepsch (1902) compared his types to unspecified series of C. f. fuscater (Colombia) and C. f. mentalis (Bolivia) distinguishing them via plumage differences: (1) chest and throat are ashen ("aschgrau", Berlepsch 1902) as in C. f. mentalis, in contrast to whitish in C. f. fuscater ("weisslich"), (2) dorsum is bluish slaty-black ("bläulich schieferschwarz"), in contrast to olive brown in C. f. mentalis ("olivenbräunliche") and "dirty brownish" in C. f. fuscater ("schmutzig bräunlich").
Hellmayr (1932) wrote, "[hellmayri is] easily distinguished from C. f. fuscater by much darker under parts, the throat and foreneck being mouse gray like the chest (instead of whitish or pale huffish smoke gray), and somewhat darker, more blackish slate back, particularly in the male sex. Besides, the tail is noticeably shorter. Wing (males) 86-90; tail, 70-75. Costa Rican birds appear to be similar to a topotypical series. No specimens from Veraguas seen."

Phillips (1991), on distinguishing hellmayri from mirabilis and "fuscater" specimens from Cerro Tacarcuna [sic]: "Darker below; throat, in museum skins, Mouse Gray (Ridgway). Less yellowish below [than mirabilis and fuscater] in life, fide Ridgely 1989."

Hybridization.—Phillips (1991) suggested that Catharus mexicanus fumosus Ridgway (1907) was described from a hybrid (C. mexicanus [Black-headed Nightingale-Thrush] x C. fuscater): "The puzzling type of fumosus approaches C. fuscater in its dark colors, long wing (88.5mm), rather heavy bill, intermediate tail-graduation (4.5mm), and perhaps somewhat shorter "crest". It resembles mexicanus in most ways, except ventrally; Iris dark brown. Bill and eyelids orange red, gonys [= culmen] black. Feet and legs lemon yellow."

Catharus f. mentalis Sclater and Salvin

Type Specimen.—Holotype is at the British Museum, London, England, specimen # ?. Collected by C. Buckley in Yunguas, Bolivia.

Diagnoses.—Sclater and Salvin (1876) described C. mentalis as a new species, closely allied to C. fuscater, on account of its brown chin and dorsum ("Supra saturate fumoso-brunneus unicolor....mento et gula cum genis brunneo indutis", p.352). It was apparently known only from the type locality until Bond (1952) described a specimen with similar plumage from Oconeque, Peru [sic]: "This specimen from southeastern Peru can not be placed with caniceps from which it differs by a strong brownish wash on the upper parts and by darker underparts. The chin, throat and fore-neck are greyish with dusky shaft-streaks, becoming darker on the chest; the sides and flanks are grey with a slight olivaceous tinge, and the lower breast and abdomen are some-what suffused with grey. It agrees fairly well in color with the description of C. f. mentalis, hitherto recorded only from the Department of La Paz, Bolivia, but is not smaller than caniceps. Its wing measures 88.5, whereas 2 adult males of caniceps from Chira have a wing of 87.5 and 90 mm, respectively."

Catharus f. mirabilis Nelson

Type Specimen.—Holotype is specimen #232933 at NMNH, an adult male collected on Cerro Pirre, in the Darién of eastern Panama, on 18 April, 1912, by E. A. Goldman.

Diagnoses.—Nelson (1913) described mirabilis from the upper reaches of Cerro Pirre (1585 m) in the Panamanian Darién, based on a type series of 12 specimens. He evidently compared this series to hellmayri only (see Chapman 1924) and neglected to specify which specimens were used in comparison (and how many). Nelson (1913) claimed that his type series differed from hellmayri in having a (1) "blacker" head, (2) "grayer" upperparts, (3) and a "yellowish" tinge to otherwise whitish underparts, but provided no quantitative comparison. After finding a series from Cerro Tacarcuna in eastern Panama (n = 13, AMNH 136159–136171) difficult to distinguish from Colombian and Ecuadorean specimens (C. f. fuscater), Chapman (1924) expressed uncertainty about the validity of C. f. mirabilis. Similarly, Hellmayr (1932) merged C. f. mirabilis with C. f. fuscater. Phillips (1991) wrote that "[mirabilis is] paler below [than hellmayri]; throat pale buffy gray (in museums)."

Catharus f. opertaneus Wetmore

Type Specimen.—Specimen #427029 at NMNH, an adult male collected in Antioquia, Colombia, on 10 June, 1950.

Diagnoses.—Wetmore (1955) described C. f. opertaneus from only two specimens (one male, one female). Its status is questionable. Both specimens are very brown and have completely black maxillae, typical of the first post-juvenal plumage in C. fuscater rangewide, but the specimen tags indicate that the gonads were enlarged (Wetmore 1955, MRH pers. obs.). Also, exceedingly few specimens of opertaneus can be found in major collections, far too few to adequately ascertain the natural degree of variation that occurs between the sexes. Additional research will be needed to determine whether opertaneus is legitimate, or if it was erroneously diagnosed from juvenile birds. The birds in the Ucumarí Regional Park of the Central Andes (see Beltrán and Kattan 2001) are not as brown as opertaneus as described by Wetmore (1955). More research is needed. For an overview of how sampling error has muddled taxonomic diagnoses in the Catharus complex, see Phillips (1991).

Catharus f. sanctaemartae Ridgway 

Type Specimen.—Specimen #8797 at the Carnegie Museum, an adult male collected by H. H. Smith, in Elheibano, Colombia, on 22 April, 1899. A paratype series (N = 9) that was collected concurrently with the holotype (Allen 1900) is housed at AMNH (#72219–72224, #72226–72227, #97770).

Diagnoses.—Ridgway (1904) distinguished the sanctaemartae holotype from hellmayri on virtue of the new taxon having uniform gray underparts, including "mouse gray" undertail coverts. Todd and Carriker (1922) found that uniform gray underparts were inconsistent in the type population, but advocated the continued use of the name sanctaemartae on account of the specimens being "less white below" and "more black on the chin" than hellmayri, although these features were admittedly not clearly marked. Interestingly, both Allen (1900) and Todd and Carriker (1922, p.406) noted that males in Santa Marta were "darker and more richly colored" than females.
Hellmayr (1932) concluded, "[C. f. sanctaemartae is] very similar to C. f. hellmayri and agreeing in mouse gray to deep mouse gray coloration of throat, foreneck, and chest; but white on under parts more restricted, usually confined to a small area in the middle of the abdomen; gray of dorsal surface lighter, less blackish slate; size larger, especially tail longer. Wing (adult, male) 90-93; tail, 77-86. This form combines the size and lighter upper parts of C. f. fuscater with the deeply colored under side of C. f. hellmayri, whose principal character is carried to the extreme by the reduction of the white abdominal zone."

Phylogenetic analyses place C. fuscater in a monophyletic clade within Catharus consisting of C. dryas (Spotted Nightingale-Thrush), C. aurantiirostris (Orange-billed Nightingale-Thrush), and C. mexicanus (Black-billed Nightingale-Thrush; Outlaw et al. 2003, Winker and Pruett 2006, Voelker et al. 2013). The former three species share an 1-bp deletion in the TRM1 gene region that is not shared by the other Catharus (Voelker et al. 2013). However, the number of C. fuscater individuals for which any DNA regions have been sequenced is extremely small (n = 3) and all of the samples were collected in South America. Outlaw et al. (2003) erroneously reported the collection location for tissue sample LSU B100003 (AKA skin voucher LSUMZ 102856) as "Panama", when the skin actually came from Bolivia. Winker and Pruett (2006) used a single specimen from Peru in their phylogenetic analyses (LSUMNS MJB593, from Peru). As such, phylogenetic analyses offer no insight into genetic differentiation among C. fuscater populations, including differences between those in Central and South America. More study is needed.