Justification of Red List Category
This species is classified as Endangered because it is confined to a single island on which high hunting pressure (both for subsistence and for trade) and habitat degradation are suspected to be a driving rapid decline in its single population within its very small range.
Carvalho (2015) estimates the population to be in the range 37,007-109,255 individuals, which roughly equates to 24,670-72,840 mature individuals.
A population decline of 30-49 % is suspected owing to hunting pressure: the species has disappeared or become scarce in easily accessible areas and hunters have reported capture rates less than half of those five years previously (F. Olmos, M. Carvalho and R. F. de Lima in litt. 2009, 2011).
Treron sanctithomae is endemic to the island of São Tomé, São Tomé e Príncipe (and formerly also nearby Ilhéu das Rolas). It was formerly abundant and remains common at some fruiting trees in forests and less well-visited plantation areas, but is now nearly absent from the most populated northeast of the island (R. F. de Lima in litt. 2011), with apparently reduced numbers at areas such as Lagoa Amelia and Monte Carmo, and hunters reporting capture rates less than half of those five years previously (F. Olmos in litt. 2007, 2008, 2009, 2011, M. Carvalho in litt. 2009, 2011).
It occurs in mature primary and secondary tropical and subtropical forest, tolerating forest fragmentation and also occurring in plantations (although it doesn't use disturbed habitat as much as mature growth). It is found from sea-level to 1,600 m, but is more common above 300 m (del Hoyo et al. 1997, Gibbs et al. 2001, Carvalho et al. 2015). It is generally sedentary but makes local elevational movements. Breeding has been recorded from November-May, with the nest built up to 3 m above the ground on a horizontal branch or in a tree fork (del Hoyo et al. 1997, Gibbs et al. 2001). It is a frugivore, feeding mainly in the canopy on a variety of fruits, particularly figs.
Hunting represents the primary threat to the species, as it is caught for consumption in rural communities and by commercial hunters to sell to bars in the capital. Some commercial hunters can kill large numbers at a time, e.g. around 30 killed and a further 30 wounded in a single morning's hunting trip (R. F. de Lima in litt. 2011, R. Rocha in litt. 2011). Hunting pressure is much greater in accessible habitats, and the species is easy to catch with slingshots or air guns (M. Carvalho in litt. 2009, 2011). Habitat loss is believed to have driven the disappearance of the species from Ilhéu das Rolas, and forest loss and degradation continues on São Tomé driven by human population growth and investment in agriculture (R. F. de Lima in litt. 2010).
Conservation 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 the benefits of these areas. A new law providing for the gazetting of protected areas has been ratified (F. Olmos in litt. 2007, 2008, 2009, 2011).
Conservation Actions Proposed
Produce science-based conservation recommendations. Ensure designated protected areas are actively protected. List it as a protected species under national law. Implement policies and raise awareness to reduce hunting pressure and to reduce off-take to sustainable levels.
Text account compilers
Butchart, S., Ekstrom, J., Symes, A., Westrip, J., Khwaja, N.
de Lima, R., Rocha, R., Carvalho, M.B., Olmos, F.
BirdLife International (2019) Species factsheet: Treron sanctithomae. Downloaded from http://www.birdlife.org on 21/10/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/10/2019.