A recently published paper suggests species level for the Caucasian subspecies Prunella modularis obscura, which is currently treated as subspecies:
Pavia M, Drovetski SV, Boano G, Conway KW, Pellegrino I, Voelker G (2021) Elevation of two subspecies of Dunnock Prunella modularis to species rank. Bulletin of the British Ornithologists’ Club, 141(2):199-210.
The Western Palearctic endemic Dunnock Prunella modularis was recently revealed to comprise three distinct genetic lineages, each distributed in different Pleistocene refugia. Specifically, one is isolated in the Iberian refugium, another is confined to the Caucasus refugium, and the third is distributed in both the Italian and Balkan refugia, as well as across broader Europe. There is a probable absence of gene flow between the refugia. Analysis of plumage and song characteristics reveals robust differences between the Iberian subspecies P. m. mabbotti, Caucasian P. m. obscura and nominate P. m. modularis. Our assessments, in conjunction with genetic isolation, support species recognition under the Phylogenetic, Biological and Comprehensive Biological Species Concepts, via qualitative and quantitative criteria, and diagnosability. We thus propose the elevation of Iberian Dunnock P. mabbotti and Caucasian Dunnock P. obscura to species level.