Data Zone
Justification of Red List category
This 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.
Population justification
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), although more surveys are required.
Trend justification
The population is inferred to be in decline due to predation from introduced mammals, hunting, and habitat degradation. 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 associated with the remaining native forest in the south of the island, where it is scarce (del Hoyo et al. 2005; Jones and Tye 2006; Dallimer et al. 2010; Fundação Príncipe 2019). 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. 900 m at least, although there is conflicting information about altitude preferences (Dallimer et al. 2010; Fundação Príncipe 2019). Recent surveys were unable to find this species in agricultural land, only locating it in primary native forest (Dallimer et al. 2012), or mature secondary forest in the vicinity of native forest (Fundação Príncipe 2019). It is believed to feed mainly on invertebrates and fruit, usually foraging on the ground and lower understory (Clement and Hathway 2000; del Hoyo et al. 2005). It nests in a shallow cup woven from moss and fine plant roots, and has been seen in tree holes and sheltered rock ledges. Nesting has been observed during the wet period between April-June, but based on the observation of juveniles, breeding potentially also occurs during October-December (Fundação Príncipe 2019). It is described as remarkably tame, and will readily approach people (Jones and Tye 2006).
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 inaccessibility of most native 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 is vulnerable to opportunistic hunting (Dallimer et al. 2010), although anecdotal evidence suggest this is unlikely to be severe (Fundação Príncipe 2019). 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, especially mammals (Dutton 1994; Birdlife International 2014).
Recent camera trap studies confirmed the presence of several introduced mammal species within the thrush’s range, including Black Rat Rattus rattus, African Civet Civettictis civetta, Feral Cats Felis catus and Mona Monkey Cercopithecus mona, which represent a plausible immediate threat through predation of adults and nests (Fundação Príncipe 2019).
Conservation and Research Actions Underway
Príncipe was recognised as a UNESCO Biosphere Reserve in 2012, and most of this species range falls within the legally designated Príncipe Obo Natural Park. This species is legally protected from hunting. The thrush also has a single species conservation action plan (BirdLife International 2014). Priority actions for improved understanding of ecology and threats, and enhanced public appreciation, are currently being implemented by Fauna & Flora International and Fundação Príncipe through a project funded by the Critical Ecosystem Partnership Fund (2018-2020). A monitoring programme is underway, in addition to ongoing projects supporting Biodiversity Conservation, Protected Area management, and sustainable management of forests in Sao Tomé and Príncipe, like the ECOFAC6 initiative 2018-2022.
Conservation and Research Actions Proposed
Research ecological requirements, namely breeding, feeding and habitat requirements. Carry out surveys to establish threats, population size and trends. Identify species-specific threats to produce conservation recommendations, particularly regarding hunting and the occurrence and impacts of predation by introduced mammals. Adopt the Principe Thrush as a flagship species for conservation on Príncipe, to develop education and raise awareness.
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
Clark, J.
Contributors
Deffontaines, J., Sinclair, F., Symes, A., Taylor, J., Westrip, J.R.S., Wright, L & de Lima, R.F.
Recommended citation
BirdLife International (2024) Species factsheet: Principe Thrush Turdus xanthorhynchus. Downloaded from
https://datazone.birdlife.org/species/factsheet/principe-thrush-turdus-xanthorhynchus on 26/12/2024.
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 26/12/2024.