Belongs within: Carduelinae.
Carduelis is a western Palaearctic genus of finches including the goldfinch C. carduelis and related species. Other species previously assigned to this genus should be placed elsewhere due to the polyphyly of Carduelis as previously recognised.
All that is gold are not finches
Published 15 February 2023
The ‘true’ finches of the Fringillidae have long been recognised as a distinct lineage of birds, distinguished by the presence of grooves at the edge of the horny palate (Zuccon et al. 2012). These grooves allow the finch to wedge grass seeds at the edge of the bill when feeding, so it can then use its tongue to remove the husks. However, the internal classification of the finches has a more fluid history. Many authors have used the genus Carduelis as a receptacle for a range of finches with relatively slender, conical bills. However, the advent of molecular studies in recent decades has confirmed that Carduelis in its broader sense is not monophyletic. In a recent reclassification of the fringillids, Zuccon et al. (2012) recommended that Carduelis be cut back to just two species: the goldfinch C. carduelis and the citril finch C. citrinella.
Of these two, the goldfinch is by far the more widespread, being native to a large part of Europe and central Asia. It has also been widely introduced to other parts of the world; I was certainly familiar with goldfinches growing up in New Zealand. Goldfinches are strikingly coloured birds with a bright red face and wings patterned with black and yellow. Females and males are largely similar in coloration except for males being brighter overall with a larger area of red on the face. Several subspecies are recognised across the species’ range though they may be divided between two broad types. Those varieties in the western part of the species’ range have a white vertical band behind the red mask and a black crown. Eastern subspecies have the head more uniformly coloured grey behind the mask, without the black crown. Arnaiz-Villena et al. (1998) suggested that goldfinch subspecies may have differentiated within the last million years as a result of populations being isolated by glaciation.
The citril finch Carduelis citrinella is a far more localised species, found in the mountains of central and southwestern Europe. At first glance, it appears quite distinct from the goldfinch, being largely yellow in coloration. As a result, many authors have included it with other yellow finches in the canary genus Serinus. However, the citril finch does have a more slender bill than canaries. It also resembles the goldfinch in its song pattern of short, repeated phrases with metallic notes, and its light, undulating flight (Arnaiz-Villena et al. 1998). Molecular data confirm its position in Carduelis. The citril finch may be more localised than the goldfinch owing to its more specialised habits, being a devotee of semi-open pine forests (Förschler & Kalko 2007).
In recent years, a third representative of Carduelis sensu stricto has been recognised in the Corsican finch C. corsicanus. This species is found on Sardinia, Corsica and neighbouring Tuscan islands. It closely resembles the citril finch with which it has often been treated as conspecific. However, the Corsican finch has a slower, more segmented song pattern than mainland citril finches. It is also more catholic in its habitat preferences, often nesting in open scrubland. Nevertheless, an acoustic study of Corsican and citril finches by Förschler & Kalko (2007) found that, while Corsican finches were recognisably distinct, there was also comparable variation between citril finch populations. They therefore suggested that the question remained open as to whether the Corsican finch was a bona fide distinct species, or simply an outlying population of citril finches. Do the distinctions between the two reflect a separate genetic history, or are they behavioral responses to the different habitat available on the islands? Are the populations truly isolated, or is gene flow maintained by occasional vagrancies? How many Carduelis are there?
Systematics of Carduelis
<==Carduelis Brisson 1760CC10 |--*C. carduelis (Linnaeus 1758)CC10 [=Fringilla carduelisCC10; incl. C. canicepsG73] | |--C. c. carduelisCC10 | |--C. c. britannica (Hartert 1903) [=Acanthis carduelis britannica]CC10 | `--C. c. parvaL81 |--C. atricepsJT12 |--C. citrinellaJT12 |--C. corsicanaJT12 |--C. dominicensisJT12 |--C. elegans Stephens 1826CC10 |--C. johannisJT12 |--C. monguillotiJT12 `--C. yemenensisJT12
*Type species of generic name indicated
References
Arnaiz-Villena, A., M. Álvarez-Tejado, V. Ruíz-del-Valle, C. García-de-la-Torre, P. Varela, M. J. Recio, S. Ferre & J. Martínez-Laso. 1998. Phylogeny and rapid Northern and Southern Hemisphere speciation of goldfinches during the Miocene and Pliocene epochs. Cellular and Molecular Life Sciences 54: 1031‒1041.
[CC10] Checklist Committee (OSNZ). 2010. Checklist of the Birds of New Zealand, Norfolk and Macquarie Islands, and the Ross Dependency, Antarctica 4th ed. Ornithological Society of New Zealand and Te Papa Press: Wellington.
Förschler, M. I., & E. K. V. Kalko. 2007. Geographical differentiation, acoustic adaptation and species boundaries in mainland citril finches and insular Corsican finches, superspecies Carduelis [citrinella]. Journal of Biogeography 34: 1591–1600.
[G73] Gauntlett, F. M. 1973. Notes on some Kashmir birds. Journal of the Bombay Natural History Society 69 (3): 591–615.
[JT12] Jetz, W., G. H. Thomas, J. B. Joy, K. Hartmann & A. Ø. Mooers. 2012. The global diversity of birds in space and time. Nature 491: 444–448.
[L81] Long, J. L. 1981. Introduced Birds of the World: The worldwide history, distribution and influence of birds introduced to new environments. Reed: Sydney.
Zuccon, D., R. Prŷs-Jones, P. C. Rasmussen & P. G. P. Ericson. 2012. The phylogenetic relationships and generic limits of finches (Fringillidae). Molecular Phylogenetics and Evolution 62: 581–596.