Justification of Red List Category
This species is threatened by a hydroelectricity project, which is projected to cause a reduction of over 50% of the total population within three generations. For this reason the species is treated as Endangered.
The population is assumed to be very small as the species avoided detection for so long. The total number of mature individuals was previously estimated at 50-249 (at least 50 in Emas National Park and up to 100 in Alto Rio Juruena, Mato Grosso). The species has since been recorded at more localities and the National Red List of Brazil estimated the population to number less than 1,000 mature individuals (MMA 2014). The population is therefore placed in the band of 250-999 mature individuals, with the largest subpopulation numbering 250-500.
Although very poorly known, outside of the protected areas in which it occurs this species's population is suspected to be decreasing owing to declines in habitat quality. An impending hydroelectric project planned for Bacia do Alto Juruena and involving the construction of five hydroelectric plants will flood the Juruena river area, which appears to be the global stronghold for the species, and could extinguish more than half of the total population in a short time (MMA 2014).
This species is known to have three apparently disjunct populations in the states of Goias, Mato Grosso and Pará, central-eastern Brazil. Until relatively recently, it was known only from the type-specimen collected in 1938 in Mato Grosso. The exact type locality is uncertain, but may have been c.400 km north-west of Cuiabá. In 2003, the species was rediscovered in gallery woodlands in Emas National Park, Goias, and since then there have been six sightings at four different locations in the park (Buzzetti and Carlos 2005, D. Buzzetti in litt. 2005), which has been estimated to hold a maximum of 1,500 km2 of suitable habitat (D. Buzzetti in litt. 2007). In 2006 another population, estimated to number perhaps up to 100 individuals (at least 40 birds were recorded), was found 900 km away along the Alto Rio Juruena, Mato Grosso (P. Develey in litt. 2007, Candia-Gallardo et al. 2010). One of the sites surveyed in this area, Juruena Telegraph Station, where the species was recorded in 2007, may be the type locality (Candia-Gallardo et al. 2010). The species is now known from Emas National Park, the basin of the Upper Juruena in Mato Grosso (Sapezal, Julio Campos, Campo Novo do Parecis and Rio Claro municipalities) and Itiquira in southeastern Mato Grosso (WikiAves 2013), and was recently recorded at Serra do Cachimbo, Pará (MMA 2014). The species is probably rare, being restricted to river margins (MMA 2014) and having avoided detection for so long, but new information on its identification and vocalisations may help to aid the discovery of other extant populations.
The type-specimen was taken amidst bushy vegetation in dry forest in the transitional zone between Amazonian rainforest and central Brazilian cerradão (closed-canopy cerrado). The closely related Black-and-white Tanager C. speculigera is rather nomadic, and this species could have similar tendencies. Evidence from Emas National Park suggests Cone-billed Tanager favours gallery forest and is strongly associated with water (Buzzetti in litt. 2007). Observations of the Alto Rio Juruena population strongly suggest that the species is associated with permanently or seasonally flooded areas of forest or grassland near rivers, and that it generally avoids unflooded cerrado savanna and gallery forest (Candia-Gallardo et al. 2010). The species appears to be territorial and perhaps monogamous, and it has been observed sallying for small flying insects and feeding on seeds, including those of bamboo and exotic grasses (Candia-Gallardo et al. 2010).
This species is likely to have suffered from forest clearance and degradation through agricultural expansion and mechanisation in the region. The spread of soya cultivation in particular poses a serious threat outside Emas National Park (Buzzetti in litt. 2007). If the species does indeed rely on flooded riverside habitats, its population may be naturally fragmented owing to the fragmented and linear nature of suitable areas; however, in this case habitat loss would be a major threat (Candia-Gallardo et al. 2010). An impending hydroelectric project planned for Bacia do Alto Juruena and involving the construction of five hydroelectric plants will flood the Juruena river area, which appears to be the global stronghold for the species, and could extinguish more than half of the total population in a short time (MMA 2014).
Conservation Actions Underway
Emas National Park is reportedly well protected and does not face immediate threats from the surrounding human population (Buzzetti in litt. 2007). It is illegal to clear gallery forest in Brazil but this regulation is poorly enforced on many private lands. A proposal has been submitted to survey the Cone-billed Tanager population in detail in the Bacia do Alto Juruena area, mapping its range, habitat usage and the extent of damage a planned hydroelectric project will have on the species.
16 cm. Black-and-white tanager. Male is mostly black. White lower breast and belly, except for black sides of belly and crissum. Small, white bases to primaries. Stout, pointed all white bill (Buzzetti in litt. 2007). Female: Olive brown upperparts, paler olive brown breast, whitish-buffy lower breast and belly. Dull olive bill (Buzzetti in litt. 2007). Similar spp. Similar in appearance to the allopatric Black-and-white tanager C. speculigera, but otherwise well distinct. Voice: The song consists of two groups of rapid musical notes, the second group slightly lower pitched, followed by a trill. This song may be repeated continuously and sounds like tchi, tchi, tchi, tchi, tchi, tchirrrrrrrrrrr, tzarrrrrrrrrrr, zíiiiiiiiiiiiiii (Buzzetti in litt. 2007).
Text account compilers
Symes, A., Wheatley, H., Capper, D., Pople, R., Taylor, J., Sharpe, C.J., Temple, H., Butchart, S., Bird, J.
Whitney, B., Hennessey, A., Develey, P., Candia-Gallardo, C., Carlos, B., Buzzetti, D.
BirdLife International (2020) Species factsheet: Conothraupis mesoleuca. Downloaded from http://www.birdlife.org on 17/02/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 17/02/2020.