This discussion was first published as part of the 2013 Red List update, but remains open for comment to enable reassessment in 2015.
White-breasted Thrasher Ramphocinclus brachyurus occurs as two subspecies: the nominate race is restricted to the Caravelle Peninsula on Martinique (to France) (Bulens et al. 1994, Temple 2005, P. Feldman and P. Villard in litt. 1998, H. J. Temple in litt. 2003), and race sanctaeluciae occurs on the north-east coast of St Lucia between the Marquis River Valley and Frigate Island Refuge (Keith 1997, J. D. Gilardi in litt. 1999). The southern subpopulation on St Lucia is believed to comprise 90% of the population on this island and 80% of the global population. It is currently listed as Endangered under criterion B1ab(i,ii,iii,v) because it has an extremely small range and is continuing to decline, thought to be due to the clearance of coastal dry woodland to make way for agriculture, housing and tourism developments.
Surveys in 2003 and 2004 indicated a global population of 1,300-2,600 breeding adults, 1,100-2,400 on St Lucia and c.200 on Martinique (Temple 2005). In 2006 and 2007, the St Lucia population still numbered about 1,200 individuals (Young et al. 2010). However, recent information suggests that the largest subpopulation of this species (on St Lucia) may be undergoing an even more rapid decline than previously thought. Analysing six years of monitoring data showed that the southern subpopulation on St Lucia had declined by 56% over this period, from 1,766 individuals in 2006 to 760 in 2011 (Morton 2012). The population on St Lucia is now estimated to be <900 birds, with <800 in the southern subpopulation and approximately 100 in the northern subpopulation (M. Morton in litt. 2012). Linear regression predicts a very severe loss (>89%) of this species during the 10 year period from 2006-2015, predicting a population size of <200 birds by 2015. These reductions are not fully understood; it is likely that they are due to factors other than just habitat loss (Morton, M. in litt 2012). By 2008, 84 ha (12% of the range of St Lucia’s southern sub-population) had been cleared for golf course/hotel construction (M. Morton in litt. 2012). The decline at the development site was shown to be less than outside this area, suggesting that invasive species could be exerting more pressure than habitat loss, or that habitat loss is having a delayed effect (M. Morton in litt. 2012). Construction was halted but if continued, a projected 248 ha (35% of the southern range) would be lost (M. Morton in litt. 2012).
If there is sufficient information to suggest that the global population of this species is projected to decline by ≥80% in three generations (15 years), this species would warrant uplisting to Critically Endangered under criterion A4b of the IUCN Red List.
Information is requested on the global population trends, size and distribution of this species. Any further comments on the proposed uplisting are also welcome.
Bulens, P. J., Le Dru, A., Tayalay, G., Bonet, J., Tanasi, M., Barré, N. and Feldman, P. (1994) Premiers resultats sur un suivi de l’avifaune de la Presqu’île de la Caravelle.
Keith, A. R. (1997) The birds of St Lucia, West Indies: an annotated check-list. British Ornithologists Union: Tring, UK.
Morton, M. N. 2012. Population trends in the white-breasted thrasher on Saint Lucia, 2006-2011. Unpubl. report to Saint Lucia Forestry Department and Durrell Wildlife Conservation Trust. DRAFT for internal circulation.
Temple, H.J. (2005) Ecology, cooperative breeding and conservation of the White-breasted Thrasher Ramphocinclus brachyurus. Thesis. Ph.D., University of Cambridge.
Young, R. P., Baptiste, T. J. N., Dornelly, A., Temple, H., Whitehead, H., Young, H. G. and Morton, M. N. (2010) Potential impacts of tourist developments in St Lucia on the Endangered White-breasted Thrasher Ramphocinclus brachyurus. Bird Conservation International 20(4): 354-364.