Data Zone
Justification of Red List category
This species qualifies as Critically Endangered because it has an extremely small population which is inferred to be in decline owing to habitat degradation and the impact of invasive predators. It is found in one site only, where it occupies a very small area of forest which, although it is not severely threatened, remains effectively unprotected and might be vulnerable in the future. Recent observations extend the known range, elevation and habitat, but the population is assumed to remain extremely small.
Population justification
The species is assumed to have a tiny population due to the scarcity of records. However, a recent extensive survey collated 39 records of this species, including many new localities, in altitude, and in secondary forest (de Lima et al. 2017). The species is very difficult to detect, so could be more abundant than current records suggest (Ward-Francis et al. 2015; de Lima et al. 2017), and whilst still likely to have a small population, the recent evidence suggests there could be >250 mature individuals. However, it is precautionarily placed in the range of 50-249 mature individuals.
Trend justification
The population is inferred to be declining as a result of ongoing habitat degradation, plus the impacts of introduced predators, however the rate of decline has not been estimated.
The species was, until relatively recently, known from just one remaining of three 19th century specimens from southern São Tomé, São Tomé and Príncipe (Steinheimer 2005; F. Steinheimer in litt. 2016). The remaining, and still only stuffed specimen, is the sole syntype of the species now housed at the Natural History Museum at Tring (UK), the other two specimens were destroyed by a fire at the Muséu Bocage at Lisbon in 1978 (Jones and Tye 2006). It was rediscovered in 1991, close to the rio Xufexufe in the south-west of the island (Sergeant et al. 1992). Since then it was sighted at nearby Formoso Pequeno (R. F. de Lima in litt. 2013) and several other localities, mostly in native lowland forest (de Lima et al. 2017; Soares et al. 2020).
This species is endemic to São Tomé, São Tomé and Príncipe, where it is believed to be confined to an area of suitable habitat between 141 km2 (de Lima et al. 2017) and 251 km2 (Soares et al. 2020). It is thinly distributed in the south and centre of the island, single birds or pairs being reliably observed at a few localities (Olmos and Turshak 2010; Solé et al. 2012). The paucity of records suggests it probably has a tiny population, but recent extensions to the known range, elevation and habitat raise the possibility that the population may prove to be larger than expected.
It was thought to be restricted to lowland, native forest, but in 2010 and 2011 it was sighted in secondary forest at 1,300-1,400 m (Solé et al. 2012). Subsequent records further support that it is not a lowland native specialist, and that its range is larger than previously assumed (de Lima et al. 2017). It is probably a canopy species and is reportedly quite silent, which could partly explain why it has so rarely been seen (Christy and Clarke 1998). It is mostly unresponsive to playback (Olmos and Turshak 2010; Solé et al. 2012). However, it seems to be easier to detected during the short dry season, when most birds are breeding (de Lima et al. 2017). It seems to move in pairs or alone and comes to the forest understorey to feed on seeds that it crushes with its powerful bill (Jones and Tye 2006; Olmos and Turshak 2010).
Historically, large areas of lowland forest were cleared for cocoa plantations. These were subsequently abandoned, creating large extents of secondary forest (Oyono et al. 2014) that are less suitable for this species (de Lima et al. 2017; Soares et al. 2020). The establishment of an oil palm plantation further increased habitat loss (de Lima et al. 2017). Other threats to habitat include the development infrastructure resulting from the ongoing population increase, and offshore oil exploitation (Oyono et al. 2014). Introduced Black Rat Rattus rattus, Mona Monkey Cercopithecus mona, African Civet Civettictis civetta and feral cats Felis catus are potential predators (Dutton 1994), although more research is needed to ascertain whether they are actually impacting the population.
Conservation and Research Actions Underway
This species is considered protected by law 11/1999, and most of its range falls within the protected São Tomé Obo Natural Park. Hunting this species is also prohibited. In 2008, a training programme with NGOs Associação de Biólogos Saotomenses (ABS) and Monte Pico was initiated to involve locals in the study and conservation of São Tomean species. During an international workshop held in February 2008 to promote ecotourism in São Tomé and Príncipe, birdwatching was listed as an activity that should be encouraged. Ribeira Peixe was identified as a suitable site for a pilot project (Olmos and Turshak 2010). In July 2009, ABS promoted a short course for the training of local people as bird guides at Ribeira Peixe. Efforts are on-going to promote the conservation of the area (Olmos and Turshak 2010).
Between 2012 and 2015, as part of the BirdLife International Preventing Extinctions programme, a species action plan was defined, involving local and international stakeholders (Ndang'ang'a et al. 2014), and local community members were key in implementing research and monitoring into the ecology, population status and threats to the species (Ward-Francis et al. 2015; de Lima et al. 2017). The Government is developing an open access database to collate all biodiversity data for the island. which will be used to inform land-use decisions (Ward-Francis et al. 2015). A workshop was held in January 2015, which included participants from the Government, to discuss progress towards an International Species Action Plan for the species (Ward-Francis et al. 2015). This 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 (BirdLife International 2019). There are several ongoing projects supporting Biodiversity Conservation, Protected Area management, and sustainable management of forests in São Tomé and Príncipe, for example, the ECOFAC6 initiative, 2018-2020. This includes activities specific to the conservation of São Tomé Grosbeak (BirdLife International 2019).
Conservation and Research Actions Proposed
Monitor population size, trends and threats. Research ecological requirements, namely concerning breeding and feeding. Ensure the implementation of existing environmental laws. Implement policies and raise awareness. Ensure that any hydroelectric developments are not within the Obo Natural Park, and incorporate species conservation measures in the Park management plan. Develop capacity for park management (Ward-Francis et al. 2015). Formally recognise the proposed buffer zone, which encompasses several areas where birds have been recorded, but which are currently unprotected (Solé et al. 2012; de Lima et al. 2017).
18 cm. Large, chunky finch with massive bill. Uniformly rusty-brown on upperparts and underparts, slightly darker on head, wings and tail. Greyish-buff bill. Similar spp. Príncipe Seed-eater Serinus rufobrunneus is much smaller. Voice Brief series of 4-5 short, 2-note canary-like whistles, with the second note higher. Similar to that of the Príncipe Seed-eater but deeper in tone, simpler and more repetitive.
Text account compilers
Clark, J.
Contributors
Ashpole, J, Benstead, P., Bird, J., Borrow, N., Dallimer, M., Deffontaines, J., Ekstrom, J., Gascoigne, A., Kaestner, P., Peet, N., Shutes, S., Sinclair, I., Starkey, M., Steinheimer, F., Symes, A., Westrip, J.R.S., Wright, L & de Lima, R.F.
Recommended citation
BirdLife International (2024) Species factsheet: Sao Tome Grosbeak Crithagra concolor. Downloaded from
https://datazone.birdlife.org/species/factsheet/sao-tome-grosbeak-crithagra-concolor on 22/12/2024.
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 22/12/2024.