Telomeres are regarded as key markers of cellular ageing and physiological state. Oxidative stress, which can accelerate telomere shortening, is thought to increase during energetically demanding processes such as bird migration. However, their study in the context of migratory behaviour is limited. Here we compared telomere length (TL) and mitochondrial DNA copy number (mitoDNAcn) between migratory and resident Eurasian blackbirds on the island of Helgoland, a migratory stopover site. Contrary to expectations, we found migrants had longer TLs despite similar mitochondrial densities. These findings reinforce the idea that migratory individuals may possess specific physiological adaptations, such as enhanced antioxidant defences, that help preserve telomere integrity.