Second documented record of the Rufous-fronted Antthrush , Formicarius rufifrons ( Aves : Formicariidae ) , in Brazil

We present the second documented record of the Rufous-fronted Antthrush Formicarius rufifrons Blake, 1957 in Brazil. The record was made in Ramal do Riozinho do Rola, 45 km north of Rio Branco municipality, Acre state. The recordings were deposited in the archives of Xeno-canto and Wikiaves. Our record represents a distribution extension of 247 km northeast of the closest known location.

The Rufous-fronted Antthrush, Formicarius rufifrons Blake, 1957, is an elusive species restricted to southwestern Amazonia and endemic to the Inambari center of endemism (Krabbe and Schulenberg 2003;Guilherme 2012).After its description in the late 1950s, the species was undetected for 24 years, until its rediscovery by Ted Parker in Cocha Cashu, Peru, close to the type locality (Parker 1983).The species occurs in Madre de Dios and Cuzco departments, Peru, and in Pando department, Bolivia (Parker 1983;Terborg et al. 1990;Kratter 1995;Schulenberg et al. 2000;Lloyd 2004).It is also found in Acre state, Brazil, at the Alto Juruá Extractive Reserve, Caipora locality (Whittaker and Oren 1999), and the Rio Acre Ecological Station (Aleixo and Guilherme 2010).It may be sympatric with the Rufous-capped Antthrush, Formicarius colma Boddaert, 1783, and the Black-faced Antthrush, F. analis (d'Orbigny & Lafresnaye, 1837), from which it is distinguished by its plumage and vocalization.
The species is considered rare and with local distribution (Stotz et al. 1996;Krabbe and Schulenberg 2003), partly due to its ecological requirements.It occurs mainly close to rivers, in high forests along floodplains, and in areas with disturbances caused by tree falls, clearings and eroded river soils with dense understory, composed mainly of Guadua Kunth bamboos, Heliconia L., and other herbaceous plants (Kratter 2009).It is considered near-threatened by BirdLife International (2016).Because of its association with riverside habitats, the species may suffer impacts from largescale deforestation, although it may adapt to altered environments, which form a mosaic along floodplains (Kratter 1995(Kratter , 2009)).
The record was made at the Ramal do Riozinho do Rola , known popularly as Ramal do Noca (09°59′44″ S, 068°12′20″ W), located 45 km north of Rio Branco municipality, Acre state, with access by the Transacreana Highway (Figure 1).The vegetation is dense forest with bamboos (Figure 2).An eight km dirt road cuts through the forest from the highway to the Rola River, a tributary of the Acre River, where new pastures and homes are found.
On 27 February 2016, at 10:19 h, during a birdwatching field trip, the typical song of Formicarius rufifrons was heard in a location with relatively little bamboo and with dense herbaceous vegetation, characteristic of early successional stages, dominating the understory (Figure 3).The location was four km from the Rola River.After hearing a single vocalization, playback was used to attract the bird and, some 10 minutes after playback, the bird started singing frequently, enabling new recordings (Figure 4).Recordings were deposited in the databases of Xeno-canto (www.xeno-canto.org;XC305252, XC307502) and Wikiaves (www.wikiaves.com.br;WA2039963, WA2053265, WA2041774).
Identification was made through the unmistakable song of the species, which is very different from other Formicarius.The song of F. colma is a more acute and rapid trill, with a shorter interval between notes than the sequence of notes of the song of F. rufifrons.The song of F. analis consists of a single note followed by a rapid sequence of about 10 notes.
The first record of the species in Brazil was made in 1995, at the Juruá River basin, Caipora locality, about 33 km from the Tejo River mouth (Whittaker and Oren 1999).On this occasion, the bird was observed foraging and was documented through recordings.This record was included in the list of birds of the Alto Juruá Extractive Reserve (Whittaker et al. 2002).The second record of the species in Brazil was made by Aleixo and Guilherme (2010) at Rio Acre Ecological Station, Purus River basin, when an individual was heard vocalizing, but there is no mention of documentation of this record.According to the criteria for documentation of ornithological records, a documented record must provide evidence of the occurrence of the species, such as collected specimens, photos, recordings or videos (Carlos et al. 2010).Therefore, this is the third locality and the second documented record in Brazil, the first for the Acre River basin and extends the species distribution 247 km northeast of the closest locality (Aleixo and Guilherme 2010).The species has been known to inhabit vegetation as far as 500 m from river banks (Krabbe and Schulenberg 2003); therefore our record (four km from the Rola River) is the furthest from a river bank.
Since the first ornithological surveys in 2015, the Ramal do Riozinho do Rola has become one of the most popular spots for birdwatching and bird photography   in eastern Acre State.The area is a priority for bird conservation in eastern Acre, with a rich avifauna associated with bamboo forests.However, it is not protected and currently suffers from invasions and illegal deforestation.

Figure 2 .
Figure 2. General view of the Riozinho do Rola road, Rio Branco, Acre State.Photo by COAG.