Finn’s Weaver (Ploceus megarhynchus): revise global threat status?

This discussion was first published as part of the 2017 Red List update. At the time a decision regarding its status was pended, but to enable potential reassessment of this species as part of the 2018 Red List update this post remains open and the date of posting has been updated.

Finn’s Weaver (Ploceus megarhynchus) is endemic to the terai (particularly in seasonally flooded grasslands [Craig 2017]) of the northern Indian subcontinent, where it is known from disjunct populations in Delhi (one record, species not seen since [A. Rahmani in litt. 2016]) and northern Uttar Pradesh, India (species has not been recorded in this area in the last five years [A. Rahmani in litt. 2016]) and adjacent extreme western Nepal, where it is a rare breeding resident and summer visitor, and from eastern Nepal (where it is a very rare non-breeding visitor) to Assam (BirdLife International 2001).

The species is currently listed as Vulnerable under criteria A2cd+3cd+4cd; C2a(i) as it has been considered to have a small population of 2,500-9,999 mature individuals, with >1,000 mature individuals per subpopulation, which is declining at a rapid rate as a result of the loss and degradation of terai grasslands, principally through conversion to agriculture and overgrazing (BirdLife International 2017). However, the population size estimate currently used is also potentially too high, with the suggestion that the population may in fact number <3,000 individuals (R. Bhargava per A. Rahmani in litt. 2012) (roughly equivalent to 2,000 mature individuals) or even <1,000 mature individuals, with potentially as low as 300 individuals (roughly 200 mature individuals) per subpopulation (R. Bhargava in litt. 2017). Additionally, trapping for the live bird trade is also a major threat to the existing fragmented population (Ahmed 2012).

Repeat surveys in the west of the species’s range, around Udham Singh Nagar District,  have shown a decline from 220 nests and 215 birds in six colonies in 2002 (Bhargava 2004) to 23 nests and 36 birds in 2016 (Bhargava in prep). Depending on whether nests or individuals are used as the key metric, this shows a decline of 83.2-89.5% over 14 years, roughly equating to a decline of 78.3-85.5% over 3 generations (12 years), and this is thought likely to continue into the future (R. Bhargava in litt. 2017).

The species will now be compared to all Red List criteria based on the current best information, and the new information available.

 

Criterion A – New information shows declines of 78.3-85.5% over 3 generations as a result of habitat loss and trapping for the live bird trade, in one area in the west of its range. If this may be considered a general trend across the entire range of the species, then this would mean that the global decline in this species is at the borderline of Endangered and Critically Endangered under criteria A2, A3 and A4. However, it should be noted that the eastern population ‘has always been seen in comparatively low numbers’ (R. Bhargava in litt. 2017) and so declines there over the most recent 3 generations potentially may not have been at as high a rate as the western subpopulation, or at the least are far more difficult to decipher.

 

Criterion B – No new information. Extent of Occurrence = 649,000km2; AOO – not measured. The species does not approach the threshold for Vulnerable under this criterion.

 

Criterion C –at the very least, the population size estimate requires moving to a lower band, probably 250-2,499 mature individuals. Combined with the fact that the minimum size of each subpopulation is potentially as low as 200 mature individuals, this implies that the species may warrant listing as Endangered under criterion C2a(i).

 

Criterion D – If the population size is considered to fall below 1,000 mature individuals, then it would warrant listing as Vulnerable under this criterion.

 

Criterion E – No quantitative analysis on extinction risk has been conducted, to the best of our knowledge.

 

Therefore, given this information, the species warrants uplisting to Endangered under criteria A2abcd+3bcd+4abcd; C2a(i). Further information from elsewhere in the range would be extremely beneficial in gauging the global rate of decline, to see whether the species may instead warrant listing as Critically Endangered under criteria A2abcd+3bcd+4abcd.

 

References

Ahmed, A. 2012. Trade in Threatened birds in India in Pp. 40-72. In: Rahmani, A. R. (2012) Threatened Birds of India – Their Conservation Requirements. Indian Bird Conservation Network: Bombay Natural History Society, Royal Society for the Protection of Birds and BirdLife International. Oxford University Press, Mumbai.

Bhargava, R. 2004. Assessing the threats and current status of Finn’s Weaver Ploceus megarhynchus in India. Indian Bird Conservation Network, Bombay Natural History Society, WWF-India and BirdLife International

BirdLife International. 2001. Threatened birds of Asia: the BirdLife International Red Data Book. BirdLife International, Cambridge, U.K.

BirdLife International. 2017. Species factsheet: Ploceus megarhynchus. Downloaded from http://www.birdlife.org on 10/07/2017.

Craig, A. 2017. Finn’s Weaver (Ploceus megarhynchus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/61006 on 12 July 2017).

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One Response to Finn’s Weaver (Ploceus megarhynchus): revise global threat status?

  1. During my work on Bengal Florican at Suklaphanta Grassland, Suklaphanta National Park, 61 Nests on two trees on May 2015 and 46 nests in one tree on one tree were seen at.
    A detail assessment of nest and population is underway in same phanta. Initial results shows- although the nest number is higher from previous opportunistic record there is high nesting failure.

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