On 1st April 2022, a 2CY male Common Chaffinch Fringilla coelebs (plate 391) was caught and ringed at Falsterbo Bird Observatory, Sweden. Its plumage was typical for a bird of the nominate European race, except that the right-hand side of the bird’s tail showed an atypically extensive area of white, formed by the presence of white on the three outermost tail feathers (plate 392). In Common Chaffinches in Europe, significant amounts of white in the tail are restricted to the two outermost feathers (R5–6). However, Common Chaffinches in North Africa (F. c. spodiogenys/africana/harterti – ‘African Chaffinch’) show a significant area of white on the three outermost tail feathers (R4–6) (van Duivendijk 2011; Corso et al. 2015). Thus, at first glance, the right-hand side of the Falsterbo bird’s tail matched that of African Chaffinch in appearance. On closer inspection, however, it became apparent that the bird had 13 tail feathers, rather than the expected 12, and that the additional feather was an outer tail feather on the right-hand side. The extra feather (‘R7’) was growing from its own feather follicle, rather than from a follicle that was already growing a feather. As a consequence of this extra feather, white in the tail was present on R5–7 on the Falsterbo bird, rather than R4–6 as it would be in African Chaffinch. The left-hand side of the Falsterbo bird’s tail was typical for a European Common Chaffinch, with substantial white on R5–6 (plate 393).
Common Chaffinch with an additional outer tail feather
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