This discussion was first published as part of the 2013 Red List update, but remains open for comment to enable reassessment in 2014.
Rusty-faced Babbler Robsonius rabori is found in northern Luzon in the Philippines and, although tape playback indicates it may be widely overlooked (del Hoyo et al. 2007), it has been described as fairly common around Adams in northwest Luzon and at Mt. Cagua in northeast Luzon (P. Hosner in litt. 2012).
It is currently listed as Vulnerable under criterion B1ab(ii,iii,v) because it was thought to have a small range, restricted to ≤10 locations, with its habitat undergoing continuing declines both in area and quality as a result of deforestation. However, P. Hosner (in litt. 2012) recently gathered information on this species’s distribution and reported that it is found in more than 10 locations, including reports in Isabela and Aurora (R. Hutchinson in litt. 2012). A research programme on mammals reported a number of new localities for this species, previously considered a lowland specialist, including in montane forest up to 1,300m (P. Hosner in litt. 2012). Observations suggest that habitat quality may not be important for this species; it might actually prefer scrubby forest (R. Hutchinson in litt. 2012) and can exist in degraded habitat (P. Hosner in litt. 2012). Also, this species is notoriously difficult to detect in the field and so it may be largely undetected (P. Hosner in litt. 2012) and more common that previously suggested (del Hoyo et al. 2007).
If this information is confirmed, and the species is found at more than 10 locations, it would no longer qualify as Vulnerable and would warrant downlisting to Near Threatened, on the basis that it approaches the thresholds for Vulnerable under criterion B1ab(ii,iii,v).
The term ‘location’ defines a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present. The size of the location depends on the area covered by the threatening event and may include part of one or many subpopulations. Where a taxon is affected by more than one threatening event, location should be defined by considering the most serious plausible threat. (IUCN 2001). For example, where the most serious plausible threat is habitat loss, a location is an area where a single development project can eliminate or severely reduce the population. Where the most serious plausible threat is volcanic eruption, hurricane, tsunami, frequent flood or fire, locations may be defined by the previous or predicted extent of lava flows, storm paths, inundation, fire paths, etc.
Further information is requested on the distribution, population size and trends of this species. Comments on the proposed downlisting are also welcome.
del Hoyo, J., Elliott, A. and Christie, D. (2007) Handbook of the Birds of the World, vol. 12: Picathartes to Tits and Chickadees. Lynx Edicions: Barcelona, Spain.