The main objective of this study was to assess the influence of surrounding forest and agricultural landscapes on the bird communities within cities. Using the point count method, we collected data and analyzed the species richness and relative abundance of breeding birds. We found differences in the species richness and relative abundance of breeding birds between urbanized areas surrounded by forests and agricultural landscapes. However, both types of landscapes significantly differed in terms of bird community structure. The highest relative abundances of bird species were observed in city forest parks and cities surrounded by forest landscapes, while the lowest abundances were detected in highly urbanized areas. Cities surrounded by forests exhibited an additional nine species compared to other areas. The ecological grouping of species revealed that cities surrounded by forests had higher relative abundances of typical forest species, such as the Great Tit (Parus major), Eurasian Blue Tit (Cyanistes caeruleus), Common Chaffinch (Fringilla coelebs), and European Pied Flycatcher (Ficedula hypoleuca), whereas cities surrounded by agricultural landscapes were characterized by bird communities adapted to open or semi-open landscapes with specific feeding and nesting behaviors. The presence of specialist forest species in the composition of urban bird communities enhances biological diversity, which is crucial for the stability of both urban ecosystems and bird communities.

Anthropogenic pressures such as over-urbanization, intensive agriculture/forestry practices, and the development of energy farms alter natural landscapes. Intensive urban development poses the greatest threat to natural ecosystems. Habitat degradation, fragmentation, and loss are among the key factors behind the current rise of biodiversity loss. In this study, we hypothesized that urbanization advances the adaptation of forest bird populations to relatively new urban ecosystems. The study was conducted in Kaunas, Lithuania, located in Eastern Europe. Genetic samples were collected in the city, representing urban landscapes, and its surrounding forests. In total, 160 nest boxes were erected, of which 80 were placed in the urban areas and 80 in the forests. Using a set of microsatellite markers, we investigated the genetic differentiation, genetic diversity, gene flow, and population structure of two common forest bird species of the Paridae family, the great tit (Parus major) and blue tit (Cyanistes caeruleus), in forests and urbanized areas. We observed low but significant differences between urban and forest great tit and blue tit populations, proving relatively high population genetic diversity. We determined that cities’ spatial structure and fragmented natural habitats can influence the formation of small and isolated bird populations (subpopulations). Urban blue tits had higher genetic differentiation and a higher tendency to form subpopulations. In conclusion, forest birds can inhabit urbanized landscapes but both great tits and blue tits respond differently to urbanization-related changes.