Justification of Red List Category
This species qualifies as Vulnerable because it is thought to have a small population, given the small area of suitable primary and mature secondary forest habitat within its range, which is tentatively inferred to be declining as a result of habitat degradation.
The population size had been previously thought to be very small. However, population density estimates (e.g. per Walther and Jones 2018) suggest that previous estimates may have been an underestimate. Based on such density estimates the population size is tentatively placed in the range 2,500-9,999 mature individuals.
The population is tentatively considered to be in decline as a result of ongoing habitat degradation.
Oriolus crassirostris is endemic to São Tomé, São Tomé e Príncipe. It is widely distributed over much of the island, except the north-east, and is most abundant in the south-west and on the central massif. It occurs everywhere at low densities, with old estimates of one to two birds per 25 ha (Atkinson et al. 1991, Christy and Clarke 1998).
It is most abundant in primary forest (up to 1,600 m), but also occurs in undisturbed secondary forest. It occurs occasionally in dry forest in the north, but is generally absent from coffee and cocoa plantations (Atkinson et al. 1991, Christy and Clarke 1998, de Lima et al. 2014).
Historically, large areas of forest were cleared for cocoa and coffee plantations. Today, land privatisation is leading to an increase in the number of small farms; the clearance of trees and may be a threat to this species where it occurs in secondary habitats. Road developments along the east and west coasts are increasing access to previously remote areas (A. Gascoigne in litt. 2000). Construction for the country's developing oil industry, including the established idea of building 'free ports' (free economic zones) (M. Melo in litt. 2003), was seen as a potential threat to the species's habitat. However, prospecting on land was unsuccessful, and any construction is likely to be offshore (F. Olmos in litt. 2007).
Conservation Actions Underway
A new law providing for the gazetting of protected areas and the protection of threatened species (A. Gascoigne in litt. 2000, M. Melo in litt. 2003) has been ratified (F. Olmos in litt. 2007). Legislation for the creation of Obo National Park has also been ratified (F. Olmos in litt. 2007) and protection of primary forest as a zona ecologica has been proposed.
20-22 cm. Forest-dwelling oriole. Male has black head, pale olive upperparts with darker wings and tail. Pale yellow upper and undertail-coverts with golden-yellow tips to tail feathers. Silky white remainder of underparts. Female lacks black head and has streaking across the breast. Juvenile similar to female but lacks yellow on tail and is more heavily streaked on underparts. Pink-red bill. Voice Melodic ou-huu, or hui-yiioouh, or hu-ou-hu.
Text account compilers
Starkey, M., Ekstrom, J., Symes, A., Taylor, J., Westrip, J., Peet, N., Shutes, S.
Olmos, F., de Lima, R., Gascoigne, A., Melo, M.
BirdLife International (2020) Species factsheet: Oriolus crassirostris. Downloaded from http://www.birdlife.org on 06/08/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 06/08/2020.