This discussion was first published as part of the 2017 Red List update. At the time a decision regarding the status of several was pended, but to enable potential reassessment of these species as part of the 2018 Red List update this post remains open and the date of posting has been updated.
Mindanao Miniature-babbler (Micromacronus sordidus) is a tiny, canopy dwelling passerine formerly considered conspecific with Visayan Miniature-babbler (M. leytensis). It is currently listed as Data Deficient, on the basis that as the species’ tolerance of forest was unknown, with the potential to be highly restrictive. Hence it has been considered that there was insufficient information to assign the species to a threat category. In recent times sightings have become regular, although only at a very limited number of locations, suggesting that it may be possible to undertake an assessment of the species’s status.
Sightings in recent years have come from forest and forest edge in the south of Mindanao. The altitudinal range of the species is 600–1,670 m with most records above 1,000 m. Within this elevation the area of forest cover has declined only slightly within the last 10 years. After rapid forest loss during the 1990s, rates of forest loss on Mindanao slowed considerably in the 2000s, and the area of primary forest has been roughly maintained on Mindanao since 2005. As a result, it can be inferred that should the species be declining, as has been assumed, it is currently likely to be only at a slow or negligible rate.
This leaves the potential extent of habitat available to the species. The area of Mindanao above the 1,000 m contour is in excess of 18,000 km2, and the species has been recorded at lower elevations. While infrequent, there are records from the majority of the separate highland areas on Mindanao suggesting that the species may occur throughout this area. If only a fifth of this area were suitable, the species would only need to occur at densities of three mature individuals per square kilometre to comfortably exceed the population threshold for listing as Vulnerable. As a tiny passerine described as common where it has been regularly observed this would seem likely to be the case. Obviously this is a very approximate approach and density estimates at even one location would be useful, but it indicates that the population is likely to exceed the threshold for listing as Threatened.
Bearing in mind the uncertainties that still remain around the species (for example, why are there no recent records from locations that appear suitable and are frequently visited such as Mount Kitanglad?), there remains the possibility that it is patchy and highly localised in occurrence, greatly reducing the potential area of occupancy and any projected population estimate. While not likely to meet the thresholds for listing in one of the Threatened categories, this uncertainty suggests that the species could be considered as Near Threatened. If it can be reasonably concluded that the species occurs relatively commonly at the sites across Mindanao where there are historical records (listed and mapped in Threatened Birds of Asia, BirdLife International 2001; species account) then the species may be listed as Least Concern.
Any information and additional recent records from the north or west of Mindanao would be particularly useful, but all comments are welcome!
BirdLife International. 2001. Threatened Birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, UK.