This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for passerines
Lynx Edicions and BirdLife International will soon publish the second volume of the HBW-BirdLife Illustrated Checklist of the Birds of the World, building off the Handbook of the Birds of the World series, and BirdLife’s annually updated taxonomic checklist.
The new Checklist will be based on the application of criteria for recognising species limits described by Tobias et al. (2010). Full details of the specific scores and the basis of these for each new taxonomic revision will be provided in the Checklist.
Following publication, an open and transparent mechanism will be established to allow people to comment on the taxonomic revisions or suggest new ones, and provide new information of relevance in order to inform regular updates. We are also actively seeking input via a discussion topic here regarding some potential taxonomic revisions that currently lack sufficient information.
The new Checklist will form the taxonomic basis of BirdLife’s assessments of the status of the world’s birds for the IUCN Red List. The taxonomic changes that will appear in volume 2 of the checklist (for passerines) will begin to be incorporated into the 2016 Red List update, with the remainder to be incorporated into subsequent Red List updates.
Preliminary Red List assessments have been carried out for the newly split or lumped taxa. We are now requesting comments and feedback on these preliminary assessments.
Large Cactus-finch Geospiza conirostris is being split into G. conirostris and G. propinqua, following the application of criteria set out by Tobias et al. (2010).
Prior to this taxonomic change, G. conirostris (BirdLife species factsheet) was listed as Least Concern, on the basis that although it had a small range, it was not believed to approach the thresholds for listing as Vulnerable under any criteria. The pre-split species was characterised as fairly common and the population was considered stable in the absence of evidence of for any declines or substantial threats. On both Genovesa and Espanola the species has been described as common (Jaramillo 2016).
G. conirostris Espanola Cactus-finch (as defined following the taxonomic change) is restricted to the island of Espanola in the south eastern Galapagos Islands, while G. propinqua Genovesa Cactus-finch is found only on the island of Genovesa in the northern Galapagos Islands. The status of the population previously listed as subspecies darwinii is unclear, having apparently bred in 1966 on Darwin but not reported since and seemingly either occurring on Wolf and Darwin as adventuring souls or the sad remnants of a lost population (Wiedenfeld 2006). Either way they do not appear to be extant at present.
G. conirostris is restricted to a single population on the island of Espanola, which has an area of approximately 60km2. As noted above, it was considered common in the 1970s though there does not appear to have been any estimate of the population size. Certainly it is still observed regularly on the island (eBird 2016), and there seems little indication of a population decline taking place. The island remains free of introduced predators, and apparently the bot-fly Philornis downsi has also not established (perhaps due to the arid nature of the island) (Wiedenfield et al. 2007), but as with Espanola Mockingbird Mimus macdonaldi (BirdLife Species Factsheet) there is a constant background risk of an introduction occurring. Indeed, Smooth-billed Ani has recently arrived on the island from introduced populations elsewhere on the Galapagos, where it has been recorded feeding on nestiling Geospiza spp. (Connett et al. 2013).
Given that the range is so restricted it is considered that the population is unlikely to exceed 2,500 mature individuals, and is estimated to number 1,000-2,499 individuals, equating to 667-1666 mature individuals, rounded here to 600-1,700 mature individuals.
It is suggested that G. conirostris is listed as Vulnerable under criterion D1 + D2.
Genovesa Ground-finch G. propinqua is in a similar predicament. Apparently still common, and certainly there are plenty of recent records from visitors to the island (eBird 2016), and the population is considered stable in the absence of evidence to the contrary. But Genovesa is only 14km2 in area. While it is likely that the population exceeds 250 mature individuals, it is equally likely to not exceed 1,000 mature individuals. The threats outlined above apply equally to this island, which is also currently free from introduced rats and likely from Philornis downsi, but Smooth-billed Ani has recently established (eBird 2016).
Consequently it is proposed to list Genovesa Ground-finch G. propinqua as Vulnerable under criterion D1 + D2
Comments are invited on these proposed categories and further information would be welcomed.
Connett, L., Guézou, A., Herrera, H.W., Carrión, V., Parker, P.G. & Deem, S.L. 2013. Gizzard contents of the Smooth‐billed Ani Crotophaga ani in Santa Cruz, Galapagos Islands, Ecuador. Galapagos Research 68, published online‐first on 15 November 2013.
eBird. 2016. eBird: An online database of bird distribution and abundance [web application]. eBird, Ithaca, New York. Available: http://ebird.org/ebird/map/lacfin1?neg=true&env.minX=&env.minY=&env.maxX=&env.maxY=&zh=false&gp=false&ev=Z&mr=1-12&bmo=1&emo=12&yr=all&byr=1900&eyr=2016 (Accessed: October 18th 2016)
Jaramillo, A. (2016). Large Cactus-finch (Geospiza conirostris). 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/62174 on 18 October 2016).
Tobias, J. A., Seddon, N., Spottiswoode, C. N., Pilgrim, J. D., Fishpool, L. D. C. and Collar, N. J. 2010. Quantitative criteria for species delimitation. Ibis 152: 724–746.
Wiedenfeld, D. A. 2006. Aves, The Galapagos Islands, Ecuador. Check List, [S.l.], v. 2, n. 2, p. 1-27. ISSN 1809-127X. Available at: <http://biotaxa.org/cl/article/view/2.2.1>. Date accessed: 18 Oct. 2016. doi:http://dx.doi.org/10.15560/2.2.1.
Wiedenfeld, D.A., Jimenez. U., Gustavo, A., Fessl, B., Kleindorfer, S. & Valarezo, J.C. 2007. Distribution of the introduced parasitic fly Philornis downsi (Diptera, Muscidae) in the Galápagos Islands. Pacific Conservation Biology. 13: 14–19.