First Evidence of Phylloscopus collybita abietinus in Sicily: A Morphological and Molecular Perspective

The "Chiffchaff complex" is a group of species with several similar subspecies, whose post-breeding distribution remains poorly understood, particularly in southern Europe. This study combines morphological and molecular approaches to investigate the subspecific composition and phenological patterns of Chiffchaffs captured in eastern Sicily. A total of 380 individuals were biometrically measured, with particular focus on wing length of P8 feather, and 81 individuals were genetically analyzed using <i>ND2</i> mitochondrial marker. Morphological analysis highlighted significant variation in P8 length between phenological groups. Assuming that a turnover of individuals from different origins may occur in the study area, genetic investigation was deemed necessary to further investigate this high morphological diversity. Phylogenetic analysis revealed high intraspecific genetic diversity and identified two subspecies in the study area: <i>P. c. collybita</i> (73%) and <i>P. c. abietinus</i> (27%). These findings genetically confirm for the first time the presence of <i>P. c. abietinus</i> in Sicily and suggest a complex pattern of seasonal co-occurrence between populations. This work contributes to the understanding of Chiffchaff migration ecology and underlines the importance of integrating ringing data with molecular tools in Mediterranean biodiversity hotspots.