Arctic Redpoll (Carduelis hornemanni) Science Article 2
Multivariate analyses were performed on four standard measurements (wing-chord, tail-length, bill-length and bill-depth) of over 1000 sexed Redpolls, including samples from all currently recognized taxa. Samples of flammea and exilipes, phenotypically defined by colour were separable biometrically, as were samples of rostrata and hornemanni. Dark Redpolls from Iceland were almsot indistinguishable from rostrata, but their average biometry was different from the pale birds breeding on the same island. Furthermore, pale birds from Iceland are different from the allopatric pale taxa exilipes and hornemanni, though they are closer to exilipes. The pale phenotype from Iceland is the most distinct Redpoll on that island, and might deserve a new name; the name islandica should be restricted to the dark, rostrata-like birds. Current taxonomic arrangements of Redpolls in two polytypic species are rather poorly founded, because most similarities in morphological criteria may be the result of convergent evolution. Mainly based on zoogeographical argument, specific rank could be assigned to hornemanni, exilipes, rostrata, and flammea.
Herremans M., ARDEA 78 (3): 441-458.