Merging subspecies distribution: potential Swedish hybrid zone and unknown migratory patterns of common chiffchaff
Hybrid zones represent crucial areas where two populations meet, mate, and produce hybrid offspring, serving as natural laboratories for studying genetic mechanisms underlying ecological traits and reproductive isolation. In Sweden, the common chiffchaff (Phylloscopus collybita) is represented by two subspecies: P. c. abietinus, which colonised northern Sweden through Finland at least 200 years ag