CR
Sao Tome Grosbeak Crithagra concolor



Justification

Justification of Red List Category
This species qualifies as Critically Endangered because it has a very small population which is suspected to be in decline owing to habitat degradation. It is found in one location only, where it occupies a very small area of primary forest which, although it is not severely threatened, remains unprotected and might be vulnerable in the future. Introduced predators could also potentially be impacting the population. Recent observations extend the known range, elevation and habitat, but the known population currently remains very small.

Population justification
The species is assumed to have a tiny population because all fieldwork has found it to be very rare and it is regularly recorded from just one area. A recent survey between July and September 2014 recorded eight birds (Ward-Francis et al. 2015), but a survey between 2013 and 2014 collated 22 records of this species (de Lima et al. 2017). It 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 having a very small population, this recent evidence suggests there could be >50 mature individuals. Therefore it is placed in the range of 50-249 mature individuals.

Trend justification
The population is suspected 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.

Distribution and population

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, 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 (F. Steinheimer in litt. 2016). 

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 near the Xufexufe in 1997 (Kaestner in litt. 1998; Sinclair in litt. 1998), and sightings continue to be reported from the Xufexufe, Ribeira Peixe (Monte Carmo) and São Miguel areas (Olmos and Turshak 2007, 2010; M. Dallimer in litt. 2002; N. Borrow in litt. 2003; F. Olmos in litt. 2007, 2008)

It was previously thought to be restricted to old-growth forest in the southern lowlands of the island, but was found further north and at higher elevations between Santa Maria and Calvário in 2010 and 2011, with further unconfirmed reports of the species at three nearby sites (Solé et al. 2012), and subsequently confirmed at nearby Formoso Pequeno (R. F. de Lima in litt. 2013). 

Further extensions to the distribution of the species have been made recently, with sightings at Morro de Dentro, the Lembá river valley, Ana Chaves Peak and the slopes of southeast Cabumbé Peak (de Lima et al. 2017). 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.

Ecology

It was thought to be restricted to lowland, closed-canopy primary forest below 500 m, but sightings between Santa Maria and Calvário in 2010 and 2011 were in degraded habitat at 1,300-1,400 m (Solé et al. 2012). 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), although the call has been recorded and some birds respond to playback (F. Olmos in litt. 2007, 2008). 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 (F. Olmos in litt. 2007, 2008). It may breed during the dry season in January-February (Ward-Francis et al. 2015).

Threats

Historically, large areas of lowland forest were cleared for cocoa plantations. Today, land privatisation is leading to an increase in the number of small farms and the clearance of trees. This does not currently affect primary forest but may be a threat in the future. Signs of palm-wine harvesting, hunting and other extractive activities are now becoming evident in the core of the Monte Carmo area (Olmos and Turshak 2010). Road developments along the east and west coasts are increasing access to previously remote areas (A. Gascoigne in litt. 2000). Plans to develop coffee plantations and restore and extend 630 ha of abandoned palm-oil plantations (to cover more than 2,000 ha; ready for harvest in 2013) in the vicinity of the core zone of Obô Natural Park and encroaching into its buffer zone (J. Tavares in litt. 2010) are likely to result in the loss of suitable habitat and potentially have both positive and negative influences on levels of disturbance (Olmos and Turshak 2010). The palm-oil project, however, reportedly incorporates the protection of some primary and mature secondary forest (J. Tavares in litt. 2010). More recent plans aim to plant 5,000 ha with oil palm, in an area that included rich secondary forest zone in the boundaries of Obô Natural Park (Barros 2013). New road networks linking oil palm concessions may increase habitat fragmentation and disturbance (Ward-Francis et al. 2015), and illegal logging in the south of the island has been identified as a further threat (Ward-Francis et al. 2015). A proposal to construct a hydroelectric dam within Obô Natural Park posed a serious threat, this project has now ceased however future power projects remain a threat (Ward-Francis et al. 2015). Introduced Black Rat Rattus rattus, Mona Monkey Cercopithecus mona, African Civet Civettictis civetta and Weasel Mustela nivalis are potential predators.

Conservation actions

Conservation and Research Actions Underway
Primary forest is protected as a zona ecologica and in Obo Natural Park, although there is no law enforcement within these areas and the lack of data about the species's ecological requirements makes it difficult to assess their benefits. However, a new law providing for the gazetting of protected areas has been ratified (F. Olmos in litt. 2007, 2008). 

As part of the BirdLife International Preventing Extinctions Programme, the Species Guardian has begun providing local community with training related to focal points in the implementation of site-based conservation and implementing an awareness-raising campaign (Steinheimer 2005).

The Government are 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).   

Initial surveys to research its population size, distribution, ecological requirements and key threats in order to produce conservation recommendations has started (de Lima et al. 2017).

Conservation and Research Actions Proposed
Continue to to research its population size, distribution, ecological requirements and key threats. Establish transects and conduct regular surveys in the south-west forests of São Tomé, clarify occurrence in new areas to the north and broaden search to other areas similar to that where the species was found in 2010-2011 (Solé et al. 2012). Ensure designated protected areas are actively protected. Ensure that any proposed hydroelectric dam developments are not within Obô Natural Park (Ward-Francis et al. 2015). Formally recognise a buffer zone encompassing the area where birds were located in 2010 and 2011 at Santa Maria and Calvário, which is located on the border of Obô Natural Park and is currently unprotected (Solé et al. 2012). Incorporate species conservation measures within the Obô Natural Park management plan and develop capacity for park management (Ward-Francis et al. 2015). List it as a protected species under national law.

Identification

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.

Acknowledgements

Text account compilers
Westrip, J., Bird, J., Benstead, P., Peet, N., Shutes, S., Starkey, M., Symes, A., Ekstrom, J., Wright, L, Ashpole, J

Contributors
Gascoigne, A., Steinheimer, F., Kaestner, P., de Lima, R., Dallimer, M., Sinclair, I., Borrow, N.


Recommended citation
BirdLife International (2019) Species factsheet: Crithagra concolor. Downloaded from http://www.birdlife.org on 16/09/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 16/09/2019.