Archived 2012-2013 topics: Vanikoro Monarch (Mayrornis schistaceus): uplist to Vulnerable or Endangered?

BirdLife species factsheet for Vanikoro Monarch Vanikoro Monarch Mayrornis schistaceus occurs on the island of Vanikoro (170 km2) and its small satellite island of Buma in the Solomon Islands. It is currently listed as Near Threatened, approaching criteria B1ab(iii); C1+2a(ii); D2 because the population was thought to be stable, with a very small range, moderately small population and is intolerant of heavily degraded habitats. Consequently, it would decline rapidly if forests within its small island range were to be commercially logged. However, the global population size is described as being ‘a few thousand individuals’ in del Hoyo et al. (2006) and so has been placed in the range of 1,000-2,499 individuals, equating to 670-1,700 mature individuals. If these estimates are confirmed, this species could warrant uplisting to Vulnerable under criterion D1, on the basis that its population may number fewer than 1,000 mature individuals. There are currently no data on population trends for this species, but if there is evidence of a population decline, this species could qualify as Endangered. The Extent of Occurrence (EOO) of this species is currently estimated at 180 km2. If the number of mature individuals and the area, extent and/or quality of habitat are in continuing decline, and the population is restricted to ≤5 locations and/or is severely fragmented, it would qualify as Endangered under criterion B1ab(iii,v). Evidence of a continuing decline may also qualify this species as Endangered under criterion C2a(ii), if the population is <2,500 mature individuals and at least 95% of mature individuals are known to be in one subpopulation. Subpopulations are defined by the IUCN 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). 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 required on this species’s population size, trends, distribution and the severity and type of threats faced by this species. Additional comments on the proposed uplisting are welcome. Reference: del Hoyo, J., Elliott, A. and Christie, D. A. eds (2006) Handbook of the Birds of the World. Vol. 11. Old World Flycatchers to Old World Warblers. Lynx Edicions, Barcelona.

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One Response to Archived 2012-2013 topics: Vanikoro Monarch (Mayrornis schistaceus): uplist to Vulnerable or Endangered?

  1. Guy Dutson says:

    As with most Pacific island species, there is very likely to be a slow ongoing population decline from habitat loss and degradation. As the primary threat is loss of habitat to subsistence agriculture, it is likely to occur at >5 locations. As with many single-island endemics, I would assess it has having a single subpopulation. On my single visit in 1998, I assessed its abundant as ‘quite common’ in forest and forest edge but not extending significantly into garden regrowth. My total of 90 encounters included the following counts: 18 in 5.5 hours, 7 in 7 hours, 5 in 7 hours, 7 in 3 hours, 6 in 3 hours, 4 in 4 hours, 12 in 9 hours, and 9 in 9 hours, all in lowland logged forest. Assuming an effective detection distance of 20m for this relatively conspicuous and vocal species, and walking at 1 km / hour, an extremely approximate calculation suggests 18+7+5+7+6+4+12+9 birds in 5.5+7+7+3+3+4+9+9 hours or 68 birds in 47.5 x 0.04 km2 = 36 birds / km2. Assuming an EOO of around 150 km2 suggests a total population of around 5000 birds

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