Justification of Red List Category
This recently-split species is estimated to have an extremely small population, occupying an extremely small range and restricted to a single island which is susceptible to the introduction of alien species. The extent and quality of habitat are in decline, which, together with a plausible threat from hunting, is thought to be driving a continuing decline in the population. For these reasons the species qualifies as Critically Endangered.
Data collected during a survey of Príncipe in 2007 were used to derive a population estimate of 364 individuals (with a 95% confidence interval of 186-887) (Dallimer et al. 2010). However, the authors consider this to be an overestimate because the species does not occupy all areas of primary forest and the data may have been biased by the species's confiding nature and habit of readily approaching humans. Thus, it is estimated that there are fewer than 250 mature individuals (Dallimer et al. 2010).
The population is considered to be in decline owing to on-going habitat loss and perhaps hunting pressure. However, the rate of decline has not been estimated.
Turdus xanthorhynchus is endemic to the island of Príncipe, São Tomé and Principe (del Hoyo et al. 2005). The taxon was discovered in 1901 (Clement and Hathway 2000, del Hoyo et al. 2005). After an absence of records since the 1920s, it was rediscovered in 1997, and has since been found to be common in the remaining forest in the centre and south of the island (del Hoyo et al. 2005, Jones and Tye 2006, Dallimer et al. 2010). It is now considered a separate species rather than a subspecies of T. olivaceofuscus (Melo et al. 2010).
The species has been recorded in primary forest from the lowlands to c. 800 m at least, although most birds occur above 400 m (Dallimer et al. 2010). Recent surveys were unable to find this species in agricultural land or secondary forest, only locating it in primary forest (Dallimer et al. 2012). It feeds mainly on invertebrates and fruit (Clement and Hathway 2000, del Hoyo et al. 2005).
The pre-split species was described as breeding from the end of July through to January, with a peak in October-December (Clement and Hathway 2000, del Hoyo et al. 2005). Its nest is a bulky cup of mixed dry vegetation and mud, covered externally with dead leaves, moss and twigs and it usually lays a clutch of two eggs (Clement and Hathway 2000, del Hoyo et al. 2005).
There is evidence that deforestation since human colonisation in the 1500s (Jones and Tye 2006) would have caused dramatic declines in this species (Dallimer et al. 2010). Deforestation is still a threat, but much reduced by the recent protection of the majority of primary forest on Príncipe (Dallimer et al. 2010). It is speculated that, as the species is very tame (Clement and Hathway 2000, Dallimer et al. 2010), it may suffer some mortality through opportunistic hunting (Dallimer et al. 2010). However, there is only circumstantial evidence from the comparison of survey data and interviews with local people that it is disappearing from areas of forest frequently used by people (Dallimer et al. 2010). Stochastic events may also be causing declines, and increased access as a result of ecotourism development could increase pressure on the species and forest resources. Being restricted to one small island, it is potentially threatened by the introduction of alien species, e.g. rats (Birdlife International 2014).
Conservation and Research Actions Underway
Most of the remaining primary forest on Príncipe is protected by Parque Natural d'Obô do Príncipe (Dallimer et al. 2010). As part of the management plan for protected areas, which is currently being drafted by the government and ECOFAC (an EU-funded conservation programme for the forests of Central Africa), the species was chosen as one of a suite of indicator species that will be monitored through regular surveys in order to assess the effectiveness of the protected areas for biodiversity conservation (Dallimer et al. 2010).
24 cm. Dull olive-brown above from head below eye to tail; head slightly darker. Chin and throat dusky buff with whitish streaks. Dark, coarse and uneven dusky-buff scaling on buff-washed breast, shading to dusky-buff scalloping on whitish remaining underparts. Underwing coverts pale orange-buff against creamy secondaries. Iris bluish-white, with a narrow yellow eye-ring. Bill large and bright yellow. Legs dull yellow. Sexes similar. Juvenile like adult with light buff flecking above and blotched brown below. Similar species T. olivaceofuscus on São Tomé is larger and has dark legs and mostly dark bill, with paler, less coarse scaling below. Its iris is dark brown to red, and it lacks a pale eye-ring.
Text account compilers
Symes, A., Wright, L, Westrip, J., Taylor, J.
de Lima, R.
BirdLife International (2020) Species factsheet: Turdus xanthorhynchus. Downloaded from http://www.birdlife.org on 29/05/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 29/05/2020.