In cities, vegetation provides critical shelter, nesting, and foraging habitat for bird species of interest. Human actions--including development and landscaping choices--determine vegetation community composition and structure.
Thus, human actions that impact vegetation are critically important to bird conservation in cities. Successful bird conservation likely requires the urban habitat (vegetation) matrix to provide enough resources for local species in addition to habitat preservation. A better understanding of how bird communities are impacted by human actions at the parcel-scale that alter vegetation communities can help guide policy and management best practices to improve matrix habitat quality and quantity.
Here, I examined how bird habitat use varies along a vegetation gradient created by different development and landscaping choices. Where previous research focused on public green space and private residential property, I expand this research to commercial office developments in King County, Washington, USA. I hypothesized that the species richness and community composition of birds found on office developments, as well as the community of foraging birds, would be explained by variables describing the outcome human actions impacting vegetation at the parcel-scale. Based on previous research on residential property, I also hypothesized that bird communities would be explained by top-down neighborhood-scale socio-economic and land cover variables.
To address these questions, I quantified the bird communities and observed feeding behavior on office developments, collected data on tree, shrub, and ground cover communities, and gathered information about neighborhood scale socio-economic and land cover variables. I used multivariate ecology tools including PERMANOVA and point-biserial correlation to detect trends in bird effective species richness and community composition.
Results/Conclusions
I found that all measures of the bird community are positively influenced by the presence of more native conifers, particularly old trees that are protected during development activities, and the presence of native shrubs. In contrast to prior research, top-down neighborhood-scale variables did not explain variation in any measures of the bird community on office developments. Importantly, I found that birds are associated with the same habitat on office developments as observed elsewhere. Together, my findings suggest an important role for developers, land owners, landscape architects, and tree protection policy in bird conservation, and a need for additional research examining how land use policy is implemented at the parcel-scale, what factors influence developer and landowner actions, and how to best incentivize actions like native conifer preservation associated with more diverse winter bird communities.