Justification of Red List Category
This species has a very small area of occupancy, which is declining, largely as a result of encroachment of invasive plant species. However, some of its subpopulations are too large for it to be considered severely fragmented; the most serious plausible threats would not affect a large enough area of habitat for the species to have ten or fewer locations and the species is not undergoing extreme fluctuations. For these reasons, the species is listed as Near Threatened.
The species is locally fairly common. Its population size was previously estimated at 17,700 mature individuals (Reinert et al. 2007), but a more recent study estimated the population at 7,511 mature individuals, based on recorded population densities and estimated areas of a range of habitats (Bornschein 2013). The population size is therefore placed in the band 5,000 - 9,999 mature individuals.
A continuing decline in population size can be inferred from the estimated reduction in the area of occupied habitat (Bornschein 2013). A study of the area of habitat within the species’s range estimated that it had decreased by 9.5% between 1978-1980 and 2013, largely as a result of encroachment of invasive plant species (Bornschein 2013), which is equivalent to a reduction of approximately 4% across three generations (14.4 years).
This species is known in a discrete area in coastal Paraná, Santa Catarina and Rio Grande do Sul, southern Brazil. It was found in 1995 in a small marsh near Matinhos city, southern Paraná coast (Bornschein et al. 1995). Subsequent surveys have found the species at Antonina, Morretes, Paranaguá, Pontal do Paraná and Guaratuba municipalities in Paraná state, and at Garuva, Itapoá, Joinville, Araraquari, Balneário Barra do Sul, Guaramirim, São João do Itaperiú and Barra Velha municipalities in Santa Catarina state (Bornschein and Reinert 1997, Reinert 2001, Reinert et al. 2007). The stronghold is Guaratuba Bay, where it is known in Ilha do Chapeu, Chapeuzinho and the lower thirds of the rios São João, Cubatão, São Joãozinho, Descoberto, Boguaçu, Preto, Parado and Alegre (Reinert 2001, Reinert et al. 2007), which holds the largest subpopulation (more than 2,700 individuals) (Reinert 2001, Reinert et al. 2007). The species has also been recorded in the municipality of Dom Pedro de Alcântara in Rio Grande do Sul (Bencke et al. 2010). All populations are restricted to small patches or narrow tracts of habitat (Reinert 2001, Reinert et al. 2007).
It inhabits littoral marshes dominated by Typha dominguensis, Fuirena robusta, Heleocharis elata, Cladium mariscus and Scirpus californicus; with other marsh vegetation (especially Asteraceae and Poaceae) such as grasses and bushes (de Lima Silva et al. 2018). It also occurs in riverine marshes, flooded plains with herbaceous vegetation and transition areas to mangrove swamps and flooded lowland forests with herbaceous strata. Most localities are subject to periodic fluctuations in water-levels. It is mostly found in pairs in low, dense vegetation less than a metre above the ground (de Lima Silva et al. 2018). It forages mostly below 60 cm and the diet appears to consist exclusively of arthropods (Reinert et al. unpubl. data.). It has a limited flight capacity, with longest-recorded flight distances of 15 m over water and 25 m over vegetation (de Lima Silva et al. 2018).
The most significant threat to this species is considered to be encroachment of invasive plant species, especially Brachiaria spp. and Hedychium coronari (Reinert et al. 2007, Bornschein 2013). Some patches of habitat, including the type-locality, are under constant human pressure and have been reduced by fires, allotments and landfills. Other threats include land acquisition, disturbance and erosion due to water traffic, sand extraction from river margins, cattle-grazing, road building and the use of plants for the production of handicrafts (Bornschein et al. 1995, Bornschein and Reinert 1997, Reinert 2001, Reinert et al. 2007, Reinert et al. unpubl. data., de Lima Silva et al. 2018). Incidents of pollution due to oil leaks have occurred; subpopulations in Paraná and Santa Catarina were affected by this threat in 2001 and at least seven of the species's subpopulation could be impacted by this threat in the future (de Lima Silva et al. 2018). The species also could be affected by sea level rise, which could greatly reduce the area of suitable habitat (Reinert et al. unpubl. data.).
Conservation Actions Underway
Listed as Endangered in Brazil (Silveira and Straube 2008, MMA 2014, de Lima Silva et al. 2018). The species is included in the National Action Plan for the Conservation of the Birds of the Atlantic Forest (ICMBio 2017). The 'Reserva Bicudinho-do-brejo' (Parana Antwren Reserve) was established in 2009 in the municipality of Guaratuba, Paraná for the protection of the species (Reserva Bicudinho-do-brejo 2008). A project completed in 2011 examined the species's area of habitat, population size and genetic variability (FUNBIO n.d.) A project is underway to translocate eggs between subpopulations with the aim of increasing genetic diversity, and to monitor the success of this action (Bornschein et al. n.d.).
13.5 cm. Medium-sized but slender antwren. The male is dark chocolate brown above and dark plumbeous below. Some have a faint white mottling on chin and malar. Dusky wings. Black wing-coverts fringed white. Blackish tail with small white tips to feathers. No whitish flank plumes. Females are paler brown above, greyer and speckled around the face. Whitish underparts, coarsely streaked blackish. Wings and tail as in the male, but browner. Voice Both sexes deliver constant whistled and repeated piu-píc or píc-piu nasal notes, and both also deliver nhééé calls and soft pic contact calls.
Text account compilers
Symes, A., Sharpe, C.J., Wheatley, H., Pople, R.
Olmos, F. & Reinert, B.L.
BirdLife International (2020) Species factsheet: Formicivora acutirostris. Downloaded from http://www.birdlife.org on 21/09/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/09/2020.