First records in north-west Europe of two Common Chiffchaff Phylloscopus collybita taxa from the Middle East and the Caucasus

Six subspecies of Common Chiffchaff Phylloscopus collybita are usually recognised, of which three are known to occur in north-west Europe: P. c. collybita, P. c. abietinus and P. c. tristis. Based on a newly developed mitochondrial DNA sequencing protocol, P. c. brevirostris and P. c. caucasicus were recorded in northwestern Europe for the first time. Both taxa occur at the south-eastern edges of the species' breeding range, in the Middle East and the Caucasus, respectively. A single P. c. brevirostris was recorded in Germany in spring (May 2022), whereas the five P. c. caucasicus were all recorded during late autumn and early winter (between the third week of November and mid-December) in the Netherlands and Germany. The contact calls of three of the P. c. caucasicus as well as the single P. c. brevirostris supported the genetic data. We postulate that P. c. caucasicus might be overlooked in Western Europe, rather than an exceptional vagrant. Movements by both taxa outside the breeding season are largely undescribed.