Urban environments are heavily anthropogenic and often species depauperate. Many bird species, however, persist or even thrive in cities, facilitated in part by the vegetated habitats many cities provide which, in some settings (e.g., intensive agriculture) may allow cities to support more species than surrounding exurban landscapes. Urban vegetation management is critical to the conservation of many bird species in cities, but such conservation requires a more comprehensive understanding of the relationships between urban birds and different types and attributes of urban vegetation than we currently possess. Our objective in this study was to identify relationships between the richness and abundance of songbird nesting guilds and urban vegetation composition and structure to help build this understanding.
We used nesting guild richness and abundance data compiled via point-count surveys of breeding songbirds and urban vegetation data from land-cover datasets and urban vegetation surveys in the Cedar Rapids and Iowa City area of Iowa, USA to construct binomial N-mixture models for four nesting guilds (tree, shrub, primary cavity, secondary cavity). Using our model results, we evaluated relationships between the abundance and richness of native songbird nesting guilds and attributes of urban vegetation and similarities and differences in these relationships among guilds.
Results/Conclusions
Relationships between some attributes of urban vegetation and environments (e.g., impervious and lawn cover) and nesting guild abundance and richness were similar among nesting guilds; however, relationships largely differed among guilds. Some characteristics of urban vegetation (e.g., tree height, evergreen trees, standing dead trees) were predictors of the richness or abundance of only one guild, while others (e.g., low vegetation) were strong predictors for multiple guilds, but with relationships that differed in their magnitude or direction. Based on these findings, we suggest that some attributes of urban environments and vegetation, for example, lawn and impervious cover, could be managed in similar ways across cities to support conservation, but that few vegetation management approaches could be applied uniformly across cities to support species in all nesting guilds. Rather, our results indicate that urban forest and vegetation management should be targeted to specific types of urban environments and to the requirements of different groups of species that occur in those environments to support a diversity of bird species and functional groups in cities.
