TWO TYPES OF DIPPER IN EXTREMADURA

There are two current taxonomy trends: (1) the recognition of new species by splitting traditional species and (2) the dwindling number of valid subspecies. The concept of subspecies is much fuzzier than that of species, and a vast number of ostensible subspecies has been built up on the basis of tiny size or plumage variations. In species of a wide range the usual process is a progressive clinical variation on a continental scale. There are many examples. In the case of the larger mammals, all well studied, the scores of described subspecies of wolves or leopards have been whittled down to a handful (even the "Iberian" wolf has lost its status though the term "signatus" is still sometimes used by inertia). The same goes for birds. Witness a recent study (Campos et al., 2010) on the White-Throated Dipper (Cinclus cinclus), with two recognised subspecies in Spain according to the usual textbooks and guides: cinclus in the northeast and centre and aquaticus in the east and southeast. The supposed distinguishing feature is the colour of the underparts below the white bib: blackish in cinclus and chestnut in aquaticus. But the authors of this work, after capturing 301 Dippers in 37 rivers from 10 different areas in Spain from 2000 to 2007, have shown that there are in fact individuals of both types in nearly all regions; three of the ten birds recaptured even showed both colour patterns on different dates. Neither were any biometric differences recorded. The conclusion is that the underparts colour is not a sufficient condition for differentiating Dipper subspecies in Spain. Nonetheless, although the range of both forms shows no clear pattern, the cinclus type was more frequent in the centre and north of Spain and was not observed in the southeast. In Extremadura only one river was sampled, for which no details have been given. In the set of six rivers sampled in Gredos a total of 55 birds were observed, 86% of them cinclus. To illustrate all the above we print below two photographs taken on the River Jerte by the colleagues of Objetivo Verde (our thanks go to José Luis Rivero).

White Throated Dipper (Cinclus cinclus): cinclus type (black underparts beneath the white bib; top photo) and aquaticus type (chestnut colour; bottom photo). River Jerte, Cáceres. Author: José Luis Rivero.

Source: Campos, F., Hernández, M. Á., Arizaga, J., Santamaría, T. & Corrales, L. 2010. The White-throated Dipper Cinclus cinclus subespecies in Spain. Ringing & Migration, 25:3-6.