Working for birds in Africa

Taxonomy of Crimson-winged Finch: a test case for defining species limits

p 136-146

Using morphology, morphometrics and vocalisations we investigated the taxonomy of the Crimson-winged Finch Rhodopechys sanguineus, which has traditionally been viewed as a polytypic species, comprising two taxa, nominate sanguineus in western and Central Asia, and alienus in north-west Africa. Few previous commentators have remarked on the obvious morphological differences between the two, although Fry & Keith (2004) recently suggested that they might be phylogenetic species. Our analyses suggest that as many as nine plumage features separate males of the two taxa (four being diagnostic and several others nearly so), and three features can be reliably used to distinguish females (of which all are diagnostic or virtually so). We also describe seasonal and age-related plumage variation in both taxa. Furthermore, morphometric data subjected to a Principal Components Analysis suggest that the two are rather better separated in size and shape than previously thought, especially in females. It proved impossible to draw adequate comparisons between the vocalisations of the two taxa, perhaps due to the available recordings being from different seasons, and certainly because of considerable individual variation in calls. Our results demand molecular testing, using especially various other members of the 'desert finches' as an outgroup, but provide strong indication that two allospecies, perhaps even full species, are involved, based on the guidelines for assigning species rank of Helbig et al. (2002). The same or a similar biogeographical pattern as found in the two Rhodopechys taxa is also evident in a number of other forms which seem best considered as being specifically distinct (e.g. African Desert Warbler Sylvia deserti and Asian Desert Warbler S. nana). Our results further reinforce the seemingly increasingly neglected importance of the museum skin in avian taxonomy, in an epoch where molecular studies appear to have acquired paramount importance (Collar 2004).

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