Abstract

Scattered records of birds with an unusual brown colour to parts of their plumage have been known for some time but, so far, the nature of this aberration has not been investigated. Aberrant reddish-brown phaeomelanin has been recorded in many species, including those whose plumage naturally contains only black eumelanin. The occurrence of a Eurasian Wryneck Jynx torquilla with such an aberration prompted further research, and a review of the records and assessment of the possible nature of the unusual phaeomelanised plumage is presented. Since 1999, ongoing research on the breeding biology of the Eurasian Wryneck Jynx torquilla has been conducted in the area around Halberstadt, Saxony-Anhalt (Wink et al. 2011; Tolkmitt et al. 2020). A Wryneck from a nestbox in the study area was ringed as a nestling on 15th July 2018, when its developing plumage appeared to be normal. It was caught again as an adult on 11th July 2020, 8.5 km from where it was ringed. Then, the primaries and, to a lesser degree, the secondaries and rectrices appeared very bleached, resulting in the usual feather patterns in these parts of the plumage being barely visible (plate 439). This effect was not apparent to the same extent in the rest of the plumage. The bird was in the early stages of its complete post-breeding moult, with several growing inner primaries, none of which showed any abnormalities.