Justification of Red List Category
This species is listed as Vulnerable because its range is estimated to be small, fragmented and declining owing to ongoing deforestation of its montane forest habitat. Its population size is unknown, but if future surveys reveal large and stable populations in high montane habitats that are less threatened by deforestation, it could qualify for downlisting to Near Threatened.
The population is estimated to number 1,000-2,499 individuals based on an assessment of known records, descriptions of abundance and range size. This is consistent with recorded population density estimates for congeners or close relatives with a similar body size, and the fact that only a proportion of the estimated Extent of Occurrence is likely to be occupied. This estimate is equivalent to 667-1,666 mature individuals, rounded here to 600-1,700 mature individuals.
Despite a lack of recent data on the status of this species, rapid population decreases are suspected to be on-going, owing to the continuing degradation of habitats throughout its range.
Basileuterus basilicus occurs in a fragmented habitat in montane areas in the Sierra Nevada de Santa Marta, north Colombia, where its abundance varies between sites from rare to locally common (Ridgely and Tudor 1989, Renjifo et al. 2002).
It inhabits the understorey and borders of stunted, humid montane forest and secondary woodland (Ridgely and Tudor 1989), frequently alongside small mountain streams and ravines (Renjifo et al. 2002), as well as in scrubby chaparral above the treeline (C. Downing in litt. 2007). It is also strongly associated with dense stands of Chusquea bamboo (Ridgely and Tudor 1989). All records are from 2,100 to 3,000 m, with the majority above 2,300 m (Curson et al. 1994, Renjifo et al. 2002). It is apparently able to tolerate moderate degradation of its habitat (Renjifo et al. 2002).
Despite possibly tolerating some habitat degradation, it is threatened by extensive deforestation, and has lost 21% of its habitat (Renjifo et al. 2002). The principal causes of deforestation are the development of cattle ranches and Pinus plantations, for example at La Cuchilla de San Lorenzo (Renjifo et al. 2002). Illegal agricultural expansion, logging and burning (Dinerstein et al. 1995, Renjifo et al. 2002) have altered all but 15% of the sierra's original vegetation (Stattersfield et al. 1998, Renjifo et al. 2002). The north slope of the Sierra Nevada de Santa Marta is the most degraded area, and this area corresponds to where the majority of birds are found. Although this species is found in two protected areas, this has not prevented extensive and continuing deforestation (Renjifo et al. 2002). Populations may also persist above the treeline in scrubby habitats, suggesting that the species may show a degree of resilience to deforestation (C. Downing in litt. 2007).
Conservation Actions Underway
It occurs within Sierra Nevada de Santa Marta National Park.
14 cm. Spectacularly marked warbler. Olive-green above and yellow below, with a bold black-and-white head pattern. Unmistakeable and easily the most distinctive member of its genus. Voice Call is a short, weak trill. The song remains undocumented.
Text account compilers
Benstead, P., Gilroy, J., O'Brien, A. & Sharpe, C J
BirdLife International (2021) Species factsheet: Myiothlypis basilica. Downloaded from http://www.birdlife.org on 20/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 20/10/2021.