The Importance of Urban Greening Spaces for Avian Communities in an Urbanized Landscape

Island ecology plays an important role in explaining various ecological and evolutionary processes. Small, isolated oceanic islands, exemplified by the Azores Archipelago, are especially vulnerable to adverse environmental conditions and human impact. The study aims to evaluate the impact of urbanization, especially the urban greening space, on the structure and dynamics of avian communities associated with various landforms in an urbanized landscape in one of the nine islands of the Azores Archipelago, São Miguel Island, in the northeast Atlantic Ocean. Samples were collected in the second half of April 2024. The line transect method (43 transects with a total of 37.4 km) was employed to count all bird species breeding in different landforms distinguished in the city: coastal land, urbanized land, rural land, and urban greening space. The obtained results showed that the number of breeding species was much higher in urban greening spaces (n = 20) than in the other lands (n = 10–14 species). Both cumulative dominance and dominance indices were much lower in urban greening space than in the other landforms. The Sørensen Index of Similarity between the four main land categories distinguished in the city varied between 0.62 and 0.96, being the lowest between the coastal and urban greening space, and the highest between the urbanized and rural lands. Two main feeding guilds were distinguished in the study area: granivores and insectivores. The former guild clearly dominated over the latter in all major land categories distinguished. Clearly, the proportion of granivores increased with urbanization. Also, two nesting guilds were distinguished: buildings and trees/shrubs. The former was dominant in all land categories except for the urban greening space where the tree/shrub nesting guild was more numerous than the building guild. The tree/shrub guild declined with urbanization. A general trend was recorded: the higher the level of urbanization, the lower the percentage of urban greening space, and in consequence, the lower the number of bird species and diversity indices, but the higher the cumulative dominance and dominance indices. The overall density of birds remains, however, distinctively similar. In the future, data on the population densities and dominance of particular species should be collected in urbanized landforms in other towns of the Azores Archipelago and Macaronesia at large.