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

## TL;DR

This study confirms for the first time the presence of a northern European Chiffchaff subspecies in Sicily using both physical and genetic data.

## Contribution

First genetic confirmation of Phylloscopus collybita abietinus wintering in Sicily using morphological and molecular methods.

## Key findings

- Genetic analysis identified two Chiffchaff subspecies in Sicily: P. c. collybita and P. c. abietinus.
- Morphological variation in wing length correlated with phenological groups, suggesting diverse origins.
- Eastern Sicily is a convergence zone for multiple migratory Chiffchaff populations.

## Abstract

The Common Chiffchaff Phylloscopus collybita is a small migratory songbird widely distributed across Europe and Asia. Within this species, several subspecies exist that are often indistinguishable in the field. This makes it difficult to understand where different populations migrate or spend the winter. In this study, we combined morphological and genetic analysis to investigate the Chiffchaff populations occurring in eastern Sicily—a key migratory stopover and wintering site in the central Mediterranean. Over a period of nearly ten years, we collected biometric data from 380 individuals and obtained samples for genetic analyses from a subset of 81 birds. A first clue of the diversity between Chiffchaffs came from the statistical analysis of wing length measurements. Genetic analysis revealed the presence of two subspecies: P. c. collybita from central and western Europe, and P. c. abietinus from northern and eastern Europe. This is the first genetic confirmation of P. c. abietinus wintering in Italy. Our findings suggest that eastern Sicily serves as a convergence zone for multiple Chiffchaff populations, highlighting its importance for the conservation of migratory birds. This study also shows how combining morphology and genetics can improve our understanding of migration patterns and diversity in cryptic bird species.

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 ND2 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: P. c. collybita (73%) and P. c. abietinus (27%). These findings genetically confirm for the first time the presence of P. c. abietinus 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.