This discussion was first published on Dec 7 2010 as part of the 2010-2011 Red List update.
Initial deadline for comments: 31 January 2012.
Eye-ringed Thistletail Schizoeaca palpebralis is currently listed as Least Concern because it was not thought to approach the thresholds for Vulnerable under any of the IUCN criteria.
Although this species has a small range, it was not believed to approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence [EOO] less than 20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be negative, the decline was not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (at least a 30% decline over ten years or three generations). The population size has not been quantified, but it was not believed to approach the thresholds for Vulnerable under the population size criterion (fewer than 10,000 mature individuals with a continuing decline estimated to be at least 10% over ten years or three generations, or with a specified population structure).
Recently, it has been suggested that this species should be listed as Endangered on the basis that it has a restricted range in which it is threatened by habitat clearance for agriculture (Engblom 2010). Although the expansion of agriculture is currently slow, the conversion of bamboo thickets to pasture and cultivation is expected to become more rapid in the near future (Engblom 2010). The species’s EOO is estimated by BirdLife at 11,500 km2, and the population is suspected to be in decline, thus it almost meets the thresholds for Vulnerable under the B criterion; however, it will only qualify if it is shown that the species occurs at fewer than 10 locations or has a severely fragmented population, i.e. over 50% of suitable habitat in patches too small to support viable populations. Note that the existence (or even a large number) of small and isolated patches is not sufficient to consider the species to be severely fragmented. For the purposes of the Red List criteria ‘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). If the species does not meet all of the thresholds for Vulnerable it may be listed as Near Threatened.
BirdLife range map for Eye-ringed Thistletail
Further information is requested regarding the number of occupied locations and the level of habitat fragmentation, as well as the likely rate of population decline, estimated number of mature individuals and the sub-population structure – specifically the maximum number of individuals in one sub-population or the maximum percentage of all mature individuals that form a single sub-population. Please note that for Red List assessments ‘sub-populations’ are defined as “geographically or otherwise distinct groups in the population between which there is little demographic or genetic exchange (typically one successful migrant individual or gamete per year or less)” (IUCN 2001).
Engblom, G. (2010) Eye-ringed Thistletail Schizoeaca palpebralis – Threatened? http://birdingblogs.com/2010/Gunnar/eye-ringed-thistletail-schizoeaca-palpebralis-threatened. Last accessed on 7 December 2010.
IUCN (2001) IUCN Red List Categories and Criteria: Version 3.1. IUCN Species Survival Commission. Gland, Switzerland and Cambridge, UK: IUCN.