- Order: Passeriformes
- Family: Tyrannidae
The Rufous Twistwing is a medium or large tyrant flycatcher that perches upright, with broad flat bill, well developed rictal bristles, and overall shaggy and rufous plumage. It is distinguished from the only other species in its genus, the Brownish Twistwing (Cnipodectes subbrunneus) by its voice, larger size, rich rufous (instead of brown) coloration, and preference for Guadua bamboo habitat.
The Brownish Twistwing (Cnipodectes subbrunneus) is smaller, browner, has a proportionately broader bill, differs in voice (by giving a cueet call), and is much more broadly distributed in South and Central America (Lane et al. 2007, Tobias et al. 2008. The two species may overlap slightly in their distributions, with the Brownish Twistwing largely inhabiting dense understory growth and tangles in terra firme forest, as well as Guadua bamboo at Camino Mucden, ~50 km from Extrema, in Bolivia (Lane et al. 2007, Tobias et al. 2008). The Rufous Twistwing has been confused with the Brownish Twistwing and Rufous Casiornis (Casiornis rufus), and potentially could be confused with other rufous passerines that also occur in bamboo habitat. Other similarly sized and rufous songbirds co-occuring in bamboo include the Dull-capped Attila (Attila bolivianus), Bright-rumped Attila (Attila spadiceus, rufous morph), and Peruvian Recurvebill (Simoxenops ucayalae). See Lebbin (2008) for further discussion of rufous morph Bright-rumped Attilas.
The Rufous Twistwing has been recording giving at least three types of vocalizations (Tobias et al. 2008):
Vocalization #1, Agitation Call (ML 124448, 124449, 124450): A loud, non-stereotyped series of 2-14 scolding notes containing 34 harmonics, given throughout the day, sometimes preceded by loud 'pyew' calls (vocalization #3). The function of this vocalization appears to be an agitation call, and is used in response to playback of call types #1 and #2 (Tobias et al. 2008). Lane et al. (2007), noted this agitation calls resemblance was similar to vocalizations by Sulphur-bellied Tyrant-Manakin (Neopelma sulphureiventer).
Vocalization #2, Song (ML 124452 [with Black-tailed Trogon Trogon melanurus singing as well], 124453): Chiming series of 5-7 notes descending in pitch. This vocalization is somewhat like the song of the sympatric Buff-throated Floiage-Gleaner (Automolus ochrolaemus). This vocalization elicited the strongest response when used in playback trials (Tobias et al. 2008).
Vocalization #3, Short call (ML 124454, 128955): A loud, whistled 'pyew' consisting of a single note with a strong harmonic, given alone or in series (couplets, triplets) and sometimes followed by a trill (Tobias et al. 2008).
Many tyrannids make sounds by snapping their bill during a variety of situations (e.g. foraging, aggression) and the Brownish Twistwing sometimes bill snaps before singing (Hilty and Brown 1986). Bill snaps may be produced by the Rufous Twistwing, but are not yet reported.
The modified primary feathers produce mechanical wing rattles, similar to those produced during flight for the Brownish Twistwing (Lane et al. 2007), and presumably function during (yet unobserved) courtship displays or aggressive displays (Lane et al. 2007, Tobias et al. 2008). Other understory birds with modified wing feathers, such as Pipra manakins and Smithornis broadbills, use these feathers for sound production during courtship displays (Tobias et al. 2008).
Detailed Description (appearance)
A medium or large Tyrant Flycatcher that perches upright, with broad flat bill, well developed rictal bristles, and overall shaggy and rufous plumage. Elongated rufous feathers with darker centers on the crown form a crest, which is usually not held erect. Body plumage and coverts generally bright rufous, tending to be brighter on chin and belly. Depending on lighting, a subtle margin between darker breast plumage and brighter belly plumage might be visible. Remiges are dusky. Adult males have twisted primaries, with primaries 8-6 showing highly modified shaft structure on the underside of each feather and a ridge along the inner web that rise above the feather plane (see also an excellent illustration of this structure is provided in Lane et al. 2007). Primaries twisted (on adult males) with Broad squared tertials have paler inner and outer edges. Dusky tertials have paler rufous margins, and are squared in shape. Upper surface of retrices are rufous, similar in color to the back. Underside of retrices is also rufous, but darker and browner than belly.
Further details of plumage are provided by Lane et al. (2007).
Eyes: Irides are red, but may appear dark from a distance in low light of bamboo thickets.
Maxila: Described as brown (Lane et al. 2004) with paler tomia. Maxila may also appear more gray or dusky than brown, with tomia color matching that of mandible.
Mandible: Pink (Lane et al. 2004).
Tarsi and toes: Gray (Lane et al. 2004).
Males tend to have larger measurements for mass and wing-length than females, but are more similar in bill dimensions and tarsus length (Tobias et al. 2008). Length and mass measures are given below, and additional measures for wing length, tail, bill length, bill width, tarsus, are available in Lane et al. (2007) and Tobias et al. (2008).
Length: 18.4-24 cm (n = 3; Tobias et al. 2008)
Mass: males measured 35 g, 40.5 g, 29.5 g (Lane et al. 2007), 42 g, 42 g, 35 g, 41 g (Tobias et al. 2008); Females measure 26.3 g (Lane et al. 2007), 22 g (Tobias et al. 2008).
Little known. Lane et al. (2007) noted that a female specimen (MUSM 26447) collected 23 February 2004 had molt on two innermost primaries, but a male collected on 25 February 2004 (MUSM 26448) had no molt. A male collected on 21 September 1997 had molt on body, and lacked the modified primaries found on other males, likely representing the first basic male plumage. Tobias et al. (2008) noted that one of the two males captured at Oceanía on 12 October 2004 was molting secondaries, upper tail coverts, and body feathers.
Brownish Twistwing (Cnipodectes subbrunneus) is the presumed sister taxa, as it is the only other species in the genus Cnipodectes.
A recent phylogenetic study of the Tyrannidae tribe Elaeniini, based on mitochondrial and nuclear DNA sequences (Rheindt et al. 2008), placed the genus Cnipodectes sister to a “flatbill” clade containing the Rhyhynchocyclus and Tolmomyias flatbills; Cnipodectes along with Rhynchocyclus and Tolmomyias, formed a clade sister to a “tody-tyrant” clade containing the genera Hemitriccus, Lophotriccus, Poecilotriccus, Oncostoma, and Myiornis, all within a Pipromorphine group.
Lebbin, Daniel J.. 2009. Rufous Twistwing (Cnipodectes superrufus), Neotropical Birds Online (T. S. Schulenberg, Editor). Ithaca: Cornell Lab of Ornithology; retrieved from Neotropical Birds Online: http://neotropical.birds.cornell.edu/portal/species/overview?p_p_spp=31406