Trogon tenellus, CABANIS, 1862

Dickens, Jeremy Kenneth, Bitton, Pierre-Paul, Bravo, Gustavo A. & Silveira, Luís Fábio, 2021, Species limits, patterns of secondary contact and a new species in the Trogon rufus complex (Aves: Trogonidae), Zoological Journal of the Linnean Society 193 (2), pp. 499-540 : 26-27

TROGON TENELLUS CABANIS, 1862

Proposed English name: Graceful black-throated trogon.

Trogon tenellus Cabanis, 1862 , Journ. für Ornith., 10 no.57, p. 173, Costa Rica. – Pothinus tenellus Cabanis & Heine, 1862 –63, Mus. Hein., part IV, p. 181. – Trogon atricollis (Race B) Grant, 1892 , Cat. Birds Brit. Mus., 17, pp. 455–458. – Trogon atricollis tenellus Richmond, 1893 , Proc. U.S. Nat. Mus., 16, p. 513. – Trogon chrysomelas Richmond, 1893 , Proc. U.S. Nat. Mus., 16, p. 513: Escondo River, Nicaragua (melaniscitc adult male) – Trogon atricollis Salvin and Godman, 1888 , Biol. Centr. Am., Aves, II , p. 458. — Trogon atricollis Ihering & Ihering, 1907 , Part. Catal. Fauna Brasil., I, Aves , p. 158, from Rio Grande do Sul to Central America. – Trogonurus curucui tenellus Ridgway, 1911 , Bull. U.S. Nat. Mus. 50 (5), p. 764. – Trogon rufus Snethlage, 1914 , Part. Bol. Mus. Goeldi. 8, p. 208. – Trogonurus curucui tenellus Cory, 1919 , Field Mus. Nat. Hist. Zool. Ser., 13, p. 325. – Trogonurus rufus tenellus Stone, 1928 , Proc. Acad. Nat. Sci. Philadelphia, 80, p. 158. – Trogon rufus tenellus Todd, 1943 , Proc. Biol.Soc. Wash. 56, p. 11. – Trogon rufus tenellus Peters, 1945 , Checklist of Birds of the World, Vol. 5, p. 157

Diagnosis: Blue, blue-grey, grey or white eye-rings differentiate it from T. cupreicauda , T. r. sulphureus and T. r. amazonicus . Blue-grey tarsi usually distinct against T. cupreicauda , T. r. sulphureus and T. r. amazonicus . Small size and poorly serrated bill compared to T. chrysochloros . Males: The uppertail is bluer than all others in the complex besides some individuals of T. r. rufus . The rest of the iridescent plumage is generally brighter than all other species, besides the upperchest and uppertail of T. cupreicauda . The chest is also warmer than all besides T. cupreicauda . Breast band presence diagnostic against T. r. sulphureus and T. r. amazonicus . The undertail black bar widths and intermediate percentage area black are generally greater than individuals of T. cupreicuada , particularly those near the contact zone but may be similar to more southerly individuals. Wing coverts usually have narrower black bars and lower percentage area black, particularly compared to southerly specimens of T. cupreicauda but may be similar to those nearer the contact zone. They also generally have a narrower black band at the tip of the uppertail compared to T. cupreicauda . Compared to T. r. rufus and T. r. amazonicus , the undertail has broader black bars, lower barring density and generally broader white bars and higher percentage area black, whilst the wing panel barring is less dense and has a lower percentage area black with generally broader white bars than T. r. rufus . From T. r. sulphureus , they differ by having wing panel barring with much narrower black bars and lower percentage area black. However, the undertail barring is similar but differs overall by having slightly broader black bars, lower density and higher percentage areas black. In relation to T. chrysochloros , the barring densities and percentage areas black of the undertail and wing panel are much lower, undertail bar widths are much broader, white wing panel bars broader but black bars generally narrower. Females: The head is generally yellower, more saturated and brighter than all other taxa. In contrast the chest is usually less yellowish but more saturated. The undertail generally has broader black bars and a higher percentage area black than all besides T. r. sulphureus , whilst the wing panel generally has a lower percentage area black than all other taxa and narrower black bars than all besides T. chrysochloros . Compared to T. cupreicauda , the plumage is generally yellower, more saturated and brighter, except against a handful of individuals near the contact zone, and lacks an extensive brown undertail wash. Compared to T. r. rufus and T. r. sulphureus , the mantle is yellower and less saturated overall, and the chest generally yellower, more saturated and less bright. The uppertail is also generally less saturated than T. r. sulphureus and southern specimens of T. r. rufus . The barring is usually less dense overall and wing panel light brown bars are generally broader than in T. r. rufus , whilst undertail and wing panel light brown bars are narrower and density higher than in T. r. sulphureus . Against T. r. amazonicus , the uppertail saturation is lower, whilst there are also subtle differences in coloration, namely a slightly less saturated mantle, and less yellow, saturated and bright chest. The undertail barring density is also slightly lower and wing panel light brown bars slightly broader. Compared to T. chrysochloros , the uppertail saturation is lower, chest less yellow and generally less saturated, baring densities lower, and wing panel light brown bars broader.

Song: Diagnosed from neighbouring T. cupreicauda by fewer notes per phrase, longer note durations and generally higher note frequencies, particularly the introductory note high frequency. Note frequencies, particularly the introductory note high frequency, are higher than for T. rufus subspecies. Fewer notes per phrase, slower pace and longer durations of notes and pause following introductory note than T. chrysochloros .

Distribution and habitat: Primary and secondary humid forests (often with bamboo) in Central America; from southern Guatemala and northern Honduras south to the extreme north-western portion of Chocó Department, Colombia. Unrecorded but presumably present in El Salvador given faunal similarities with neighbouring countries. Up to an elevation of 1300 m.

Type material: Holotype: (missing) ZMB 16402 (subadult male) collected by Frantzius, V from ‘ Costa Rica’. Last recorded in the Museum für Naturkunde – Leibniz Institute for Evolution and Biodiversity Science, Berlin (MfN).

Description: Small body size, similar to T. cupreicauda , but overlapping substantially with T. rufus . Shortest tail length of all taxa. Bill poorly serrated. Males: Uppertail mostly blue green but varying from deep blue to plain green. Individuals with shiny olive-green uppertails (> 554 nm) are rare with only a single record (UCLA 22738) from Costa Rica, far from the contact zone with T. cupreiauda . Subterminal band absent. Head and mantle copperygreen. Rump typically plain-green. Chest usually bright golden-green. Belly yellow. The breast band is usually complete, sometimes inconspicuous and rarely absent. The undertail barring has broad black bars, relatively broad white bars, low density and moderate percentage area black, whilst the terminal tailband is generally narrow. The wing panel barring has narrow black bars, relatively broad white bars, low density and low percentage area black. Females: Head generally yellower, more saturated and bright Dark Brown to Dark Yellowish Brown, occasionally even Dark Olive Brown or rarely Very Dark Brown. Mantle generally yellower, poorly saturated Dark Olive Brown to Dark Yellowish Brown. Chest moderately to more yellow, more saturated, light to dark Olive Brown, Dark Olive Brown to Dark Yellowish Brown. Belly yellow. Uppertail moderately saturated Dark Reddish Brown. Undertail wash limited to the base of the rectrices, or completely absent, with only a small fraction present in which it edges the black at the base of the rectrices (not visible in natural position). Undertail barring with broad black bars, narrow white bars, moderate density and high percentage area black. Wing panel barring with narrow black bars, moderate light brown bars, moderate density and generally low percentage area black. Bareparts: Eye-ring, in males, usually blue, sometimes blue-grey with small minorities grey or green. In females, the eye-ring is usually blue-grey and less often blue. Tarsi usually grey or blue-grey in both sexes, the later usually distinctive against T. cupreicauda , with small minorities pink to purplishgrey in females and a single male recorded with olive.

Song: Distinctively feeble song with few notes per phrase, moderately slow pace, relatively long introductory note and loudsong note durations, moderately long pause after the introductory note, introductory note moderately high peak and low frequencies and high high-frequency, loudsong notes moderately high peak and low frequencies and high high-frequency. Narrow introductory and loudsong note bandwidths. A particularly large proportion of recordings contained two-note phrases (30.6%) compared to all other taxa.