<p>Urbanisation is a prevalent form of anthropogenic environmental change, reshaping landscapes and altering the availability and composition of natural resources. In birds, such transformations influence a range of traits, from breeding phenology to behaviour, morphology and ornamentation. While most research has focused on how urbanisation impacts avian breeding, other key stages of the annual cycle remain overlooked, despite their importance for future fitness. This study examines how urbanisation shapes dietary patterns in great tits (<i>Parus major</i>) during two critical phases: the pre-laying and moulting periods. Using a metabarcoding approach on faecal samples collected in the city of Montpellier and surrounding rural areas, we assessed dietary composition. In addition, we measured moult patterns and yellow plumage colouration, the latter reflecting nutritional quality and exhibiting urban-specific variation. Urban individuals had consistently more diverse diets than their rural conspecifics, in both pre-laying and moulting periods, with birds consuming a broader range of both plant and invertebrate taxa. Reversely, we found no habitat-related difference in the timing or extent of the moulting period; however urban birds exhibited a yellow plumage that was 47% paler than rural birds during the moulting period. Our results suggest reduced availability of preferred food items in cities, prompting birds to exploit more diverse and potentially lower-quality resources. It remains to be determined to what extent urban dietary shifts contribute to the documented phenotypic divergence in colouration during moult and to lower reproductive success in spring.</p>