Archived 2010-2011 topics: Samoan Flycatcher (Myiagra albiventris): still eligible for Vulnerable?

Link to BirdLife species factsheet for Samoan Flycatcher

Samoan Flycatcher Myiagra albiventris is listed as Vulnerable under criteria A2c; A3c; A4c on the basis that its population is suspected to be declining at a rate of 30-49% over 10 years owing to habitat degradation caused by severe cyclones in 1990 and 1991 and the spread of non-native tree species, as well as deforestation for agriculture. This threat listing has been questioned in the past (Sherley 2001) and recently it has been expressed that this species may no longer qualify as Vulnerable (G. Dutson in litt. 2009), provoking a review of its status.

Recent survey results suggest that the species is recovering, with ‘healthy populations’ of 20-30 birds recorded in Important Bird Areas (IBAs) and records from many other areas, with informal observations of pairs along roadsides and near habitation (Schuster 2010). If the population trend is stable or increasing the species may be eligible for downlisting. However, if the species is still declining, albeit less rapidly, it may still qualify as Vulnerable under criterion C1, as its population is estimated at 2,500-9,999 individuals (thus there are almost certainly fewer than 10,000 mature individuals), and the population trend may still represent a decline of at least 10% over 13 years (estimate of three generations). Eligibility for Vulnerable status under criterion C2 does not require an estimate of the population trend; however, all individuals must be shown to form one sub-population; M. albiventris is thought to have two sub-populations, although it is apparently not known to what extent individuals of this species move between Savai`i and `Upolu.

The species’s Extent of Occurrence (EOO) is estimated at 2,900 km2; however, it does not qualify for threatened status under the B criterion (EOO of less than 20,000 km2 accompanied by an ongoing decline) as its habitats are not regarded as severely fragmented and it is recorded at more than 10 locations. 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). As the main threats to M. albiventris include cyclones, it could be considered to occur at only one location. Habitat fragmentation would be considered ‘severe’ if more than 50% of suitable habitat was is patches too small to support viable populations.

Up-to-date information is requested for this species, including the estimated population size, current population trend over 13 years and the severity of threats.

IUCN (2001) IUCN Red List Categories and Criteria: Version 3.1. IUCN Species Survival Commission. Gland, Switzerland and Cambridge, UK: IUCN.

Schuster, T. C. (2010) Important Bird Areas of Samoa. Pacific Environment Consultants Limited.

Sherley, G. (2001) Bird Conservation Priorities and a Draft Avifauna Conservation Strategy for the Pacific Islands Region. Apia, Samoa: South Pacific Regional Environment Programme.

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2 Responses to Archived 2010-2011 topics: Samoan Flycatcher (Myiagra albiventris): still eligible for Vulnerable?

  1. Guy Dutson says:

    Based on two visits to Samoa (most recently in 2009), when one to five individuals of this species were seen on most days in forest habitats, I would suggest that the population is indeed 2500-9999 individuals. As the species occurs relatively commonly in degraded and regenerating forest habitats, I would suggest that cyclones are an intermittent threat causing transient declines in the population but that the fundamental threat is small-scale habitat loss to shifting agriculture. I would not support an estimated decline of 30-49% over 10 years. A decline of 10% over 13 years is plausible but would need some data on the rate of forest loss. Based on the variation between populations of neighbouring congeners on somewhat more distant islands than Savai`i and `Upolu (notably M. ferrocyanea, M. vanikorensis and M. caledonica), I would suggest that that there is little exchange between the sub-populations on Savai`i and `Upolu and these should be considered to be separate sub-populations.

  2. Mark O'Brien says:

    Little more to add. The field data undertaken in 2009 by Schuster et al recorded 20 birds on 27 point counts on the Aleipataa Islands. 3 point counts at each of 9 locations – all locations recorded the bird on at least one of the point counts. Also 9 point counts undertaken at separate sites in Eastern Upolu recorded 10 birds at 7 of the sites. These point counts were all undertaken in potential IBA sites – so don’t represent ‘average’ scores for Samoa as a whole.

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