Contrasting long-term trends of bird taxonomic, functional, and phylogenetic diversities along an urban gradient

Long-term monitoring of bird communities is fundamental to disentangle the effects of urbanization on bird populations. However, the interannual changes of different diversity facets, such as taxonomic, functional, and phylogenetic diversities, have not been analyzed along urban gradients. This study examined the temporal trends of bird species richness and functional and phylogenetic diversities over 23 years along an urban gradient in Mar del Plata City, Argentina. Birds were surveyed on transects in urban, suburban, and periurban habitats for 13 years during 2002–2024. Functional and phylogenetic diversities were assessed through null models considering variations in species richness. Bird species richness increased during the study period in the three habitat types. Functional diversity remained stable in the urban habitat and increased in suburban and periurban habitats. These changes were associated with temporal increases in several functional groups, such as carnivores, nectivores, and frugivores. Phylogenetic diversity in the urban habitat turned from random to clustered, which was associated with increases in the abundance of Columbiformes. The assembly of suburban and periurban bird communities turned from random to phylogenetically overdispersed. These changes were related to increases in abundance of Falconiformes and Apodiformes. The results showed that, without significant changes in the urban landscape, there were substantial changes in the assembly of communities. The more urbanized sites constituted a filter for bird species, not allowing the colonization of several bird species that have increased their abundances in the region.