By Martin Collinson, Amanda Murcia Sanches, Gustavo Ferreira, Kirsty Dewars, Florence Roberts and Thomas Shannon
Abstract Three subspecies of Common Chiffchaff Phylloscopus collybita have occurred in Britain. ‘Siberian Chiffchaff’ P. c. tristis is now recognised as a scarce but regular migrant to western Europe, but the extralimital status of presumed Scandinavian individuals of P. c. abietinus is uncertain. Identification issues and the problem of abietinus x tristis intergrades remain. This paper summarises the results of genetic analyses of 149 migrant and wintering Chiffchaffs in Britain & Ireland during 2009–17. Genetically confirmed Siberian Chiffchaffs were found to be primarily late-autumn migrants, with a number of overwintering birds and a small peak of early spring migrants. Most Siberian Chiffchaffs in Britain & Ireland are males. In our sample, abietinus was much less frequent than tristis; this subspecies is probably overlooked, with records in late autumn, winter and a few in the late spring.