How do the features of individual gardens affect bird diversity in rural-suburban areas?

Demographic data show booming metropolitan populations and the related rapid spread of urbanized areas. Cities already harbor numerous diverse habitats, including gardens, varying greatly both in terms of floristics and architectural attributes. The way gardens are designed and managed is of crucial importance for the birds associated with them. The present work provides a comprehensive overview of garden features, which were used in cluster analysis to distinguish several garden types. The birds occurring in gardens located on the outskirts of the city in southern Poland were analyzed in three phenological periods (breeding season, autumn, winter).Depending on garden type, bird density ranged from 10.8 to 57.4 breeding pairs per ha, with 0.8–8.3 species per garden. The species similarity Jaccard index of bird assemblages was from 0.10 to 0.75. The evenness index revealed some garden types with very even species distributions, as well as some types that were strongly dominated by a single species. Garden features also affected proportions between groups of species with different nesting preferences (cavity nesters, canopy nesters, birds nesting in building, and those nesting in shrubs and near the ground). The function of gardens as food sources increased from spring to winter. The garden attributes that significantly affected the occurrence of breeding birds were high tree density and hedges, building walls and attics available for birds, as well the presence of chicken coops. In terms of feeding, of importance was not only lush vegetation, but also places where different types of food were provided for birds, poultry, and domestic and farm animals.As the unfolding changes in urban and suburban areas are likely to result in the disappearance of some garden features and the associated niches, it will be necessary to compensate for them with a view to conserving bird species such as the house sparrow. To that end, appropriate educational and advisory programs should be offered to garden owners.