Data Zone
Justification of Red List category
This species is suspected to be declining rapidly owing to habitat loss and degradation, largely due to conversion to agriculture and tree plantations. It is therefore classified as Vulnerable.
Population justification
It appears to be scarce and localised (Pearman and Abadie 1995). Almost all records are of lone individuals, although six individuals were recorded at a wetland site in Rio Grande do Sul (Accordi 2002), the species is observed daily at Reserva Natural Rincón de Santa María, Corrientes (Fariña et al. 2018, Bodrati et al. 2019), and there are known populations at Campo San Juan, Misiones, and possibly at Reserva Natural Provincial Iberá, Corrientes (A. Bodrati, N. Fariña and K. Cockle in litt. 2021). However, the species's apparently scarcity may result at least partially from it being a cryptic, nocturnal species that is often difficult to study. Surveys from 1999-2006 in the coastal plain of Rio Grande do Sul estimated a population of 12 breeding pairs at Capao Novo (218 ha), and 20 breeding pairs at Banhado dos Pachecos (2,544 ha; Accordi 2008).
Based on the minimum and first quartile densities estimates of other nightjar species (0.3 and 0.9 individuals/km2, respectively), the area of the mapped extant range, and assuming 3-10% occupancy, the population size may be calculated to fall within the range 5,000 - 52,000 individuals. However, given the small number of records, the true population size is suspected to be smaller than this (K. Cockle in litt. 2020), so it is here placed in the band 2,500 - 52,000 individuals.
The subpopulation structure is not known, but based on the disjunct range, there are assumed to be at least three subpopulations.
Trend justification
The species's range appears to have contracted considerably over recent decades, so the species's population size is inferred to be declining. It is suspected that the species has lost around half of its range in Argentina over 25 years since the 1990s (A. Bodrati, N. Fariña and K. Cockle in litt. 2021). It is almost certainly extirpated from Buenos Aires, and almost all habitat in Entre Rios has been destroyed (A. Bodrati, N. Fariña and K. Cockle in litt. 2021). The species was recorded in Santiago del Estero (M. Rumboll in litt. 1986), El Palmar National Park, Entre Rios, in 1985 (M. Nares and D. Yzurieta in litt. 1986), and Colon, Entre Rios in 1979 (M. Nares and D. Yzurieta in litt. 1986). In the 1990s, four records were made at three sites in Sao Paulo State, Brazil (Kirwan et al. 1999). In the absence of recent records, the species is now presumed to be locally extinct in all of these regions. The species was known to occur at Puerta Boca, Entre Rios, until around 2000, but the wetland habitat there has since been destroyed (A. Bodrati, N. Fariña and K. Cockle in litt. 2021).
Based on the reduction of the area of the mapped extant range, the species is estimated to have lost approximately 60% of its range since the 1980s. Assuming a constant rate of habitat loss, the species is suspected to have undergone a reduction of 10-19% over the past decade. Assuming that the same area of range continues to be lost per year, up to 46% of the species's remaining range may be lost over the next ten years, so an equivalent population reduction is suspected.
Eleothreptus anomalus has been recorded at few fragmented sites in eastern Paraguay (Hayes 1995, Lowen et al. 1996, Capper et al. 2001), north Argentina, and central and south-east Brazil (Bornschein et al. 1996, Kirwan et al. 1999). In Paraguay, the only reliable known breeding area is on Isla Yacyretá in the Paraná River (Smith 2013). In 2010, it was reported that an individual was recorded in Tocantins, Brazil (Pacheco and Olmos 2010), but there have been no further records to confirm the species's presence in the state. In Argentina, the species's remaining stronghold is in Corrientes, although it is only encountered regularly at a few sites (eBird 2021, A. Bodrati, N. Fariña and K. Cockle in litt. 2021). There are few confirmed localities in Misiones, and little remaining well-preserved grassland habitat in the province (A. Bodrati, N. Fariña and K. Cockle in litt. 2021).
The species formerly had a much larger range. It has almost certainly been extirpated from Buenos Aires, and almost all habitat in Entre Rios has been destroyed, although a small number of individuals may persist (A. Bodrati, N. Fariña and K. Cockle in litt. 2021). In Santiago del Estero and north of Cordoba there is a small area of remaining habitat where a population could persist, but there are no recent records (A. Bodrati, N. Fariña and K. Cockle in litt. 2021). Single birds recorded in Santiago del Estero (M. Rumboll in litt. 1986), El Palmar National Park, Entre Rios, in 1985 (M. Nares and D. Yzurieta in litt. 1986), and Colon, Entre Rios in 1979 (M. Nares and D. Yzurieta in litt. 1986), and in the 1990s, four records were made at three sites in Sao Paulo State, Brazil (Kirwan et al. 1999). Despite ornithological surveys (López Lanus et al. 2013), there have been no recent records from these areas, and so the species is now presumed to be locally extinct.
The species's ecology is poorly-known, and it has been recorded in a wide range of habitats, including gallery forest, monte (chaco-type woodland) and transitional woodlands (Pearman and Abadie 1995), savannas and grasslands, marshland, swamps, campo cerrado, lagoon edges with spiny scrub, and along streams, pools and flooded palm groves (Straneck and Viñas 1994, Cleere and Nurney 1998, Kirwan et al. 1999, Accordi 2002). It was previously thought to be most strongly associated with forest habitats (Pearman and Abadie 1995), but observations at key breeding sites in Argentina and Paraguay suggest that it is a grassland specialist and may be associated with flooded grasslands in parts of its distribution (Fariña et al. 2018, Bodrati et al. 2019). It has been suggested that it may be a migrant in the southern part of its range, with individuals breeding in Argentina migrating north in winter (Pearman and Abadie 1995), but at least some individuals are resident year-round in Corrientes (Argentina; Bodrati et al. 2019), and more recent evidence suggests that individuals may disperse over long distances outside the breeding season (Guest et al. 2020). It is a nocturnal aerial insectivore. It appears to have a lek- or lek-like mating system, with males gathering to display at arenas from August to December (Smith 2013, Fariña et al. 2018).
Grasslands and chaco habitats throughout its distribution are being rapidly destroyed by extensive cattle ranching, arable agriculture, wildfires and seasonal burning, wetland drainage, excessive use of pesticides and afforestation with Pinus and Eucalyptus spp. (Pearman and Abadie 1995, Dinerstein et al. 1995, Lowen et al. 1996). In recent decades, agricultural expansion has pushed cattle ranching onto marginal lands (Marino et al. 2013) where overgrazing likely degrades habitat, rendering many pastures unsuitable (A. Bodrati in litt. 2020). In central Argentina, where the species has not been recorded in decades, grassland habitat has been largely destroyed due to tree plantations (K. Cockle in litt. 2020). Wetland habitat along the Rio Uruguay has been extensively drained and converted to croplands and urban areas (A. Bodrati, N. Fariña and K. Cockle in litt. 2021).
In eastern Paraguay, remaining grassland is fragmented within a matrix of industrial agriculture (K. Cockle in litt. 2020).
Conservation Actions Underway
It is listed nationally as Endangered in Argentina (MAyDS and Aves Argentinas 2017) and Paraguay (Ministerio del Ambiente y Desarollo Sostenibile 2019) and Near Threatened in Brazil (MMA 2014). In Brazil, it occurs in Brasília and Serra da Canastra National Parks and Cambuí Biological Reserve. It has been recorded from Rincón de Santa María and Urutaú Nature Reserves, Argentina (del Hoyo et al. 1999, Fariña et al. 2018, Bodrati et al. 2019). In Paraguay, Isla Yacyretá, which has the only reliable known breeding population in Paraguay, has been designated as a reserve (Smith 2013), and there are records from the San Rafael National Park (Smith and Clay 2015, Esquivel et al. 2019), Ybytyruzu Management Reserve and Tapyta Private Nature Reserve (Esquivel et al. 2019).
The Southern Cone Grasslands Alliance was established in 2006 to promote sustainable ranching practices across the grasslands of southern Brazil, Uruguay, southeast Paraguay and northeast Argentina, and a certification scheme has been developed to provide a financial incentive for sustainably-produced beef (Azpiroz 2012). At Rincón de Santa María Provincial Reserve, park rangers have been monitoring the population since 2009 and are working to restore grassland habitat (Fariña et al. 2018).
Text account compilers
Wheatley, H.
Contributors
Babarskas, M., Capper, D., Sharpe, C.J., Benstead, P., Symes, A., Cockle, K., Bodrati, A. & Fariña, N.
Recommended citation
BirdLife International (2024) Species factsheet: Sickle-winged Nightjar Eleothreptus anomalus. Downloaded from
https://datazone.birdlife.org/species/factsheet/sickle-winged-nightjar-eleothreptus-anomalus on 22/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 22/11/2024.