Using urban forestry assessment tools to model urban bird habitat potential

Background/Question/Methods

The replacement of forest cover with urban features such as buildings, roads, exotic vegetation, lawns and other impervious surfaces poses one of the greatest threats to bird diversity for cities developed in forests. As more land becomes slated for urban development, identifying effective urban forest management tools becomes paramount to ensure the urban forest provides habitat to sustain bird and other wildlife populations. The primary goal of this study was to integrate wildlife suitability indices to a national urban forest assessment tool, i-Tree. To achieve this goal, we quantified the available urban habitat using datasets from eleven northeastern American cities that were analyzed using i-Tree, and summarized bird habitat relationships for variables that directly related to these datasets. With these data, we generated habitat suitability indices for ten bird species that have varying life history traits and conservation status. We then calculated the relationship between the i-Tree urban habitat variables and the suitability index to generate an equation for predicting the probability of a species occurrence for the selected habitat variables. We applied these equations to the urban forest datasets to calculate the overall habitat suitability for each city and the habitat suitability for different land-use categories for each bird species.

Results/Conclusions

Important habitat variables included tree density, tree size, basal area, the presence of deadwood, canopy coverage, and forested area. Preliminary results suggested that suitability varied for each species amongst cities. For example, of the eleven cities, Philadelphia, PA had the highest suitability score for the red-bellied woodpecker, while Jersey City had the lowest (0.47 and 0.17 respectively). In addition, red-bellied woodpecker habitat suitability varied for different land-uses amongst cities; parklands and golf courses had the highest suitability scores for Philadelphia (0.8, 0.7, respectively), while vacant lots and low density residential areas had the highest suitability scores for Boston, MA (0.7 and 0.6, respectively). Mean canopy cover for parklands in Philadelphia was 75% and for vacant lots in Boston was 55%. Tree density for these respective land-uses for each city was 16 and 11 trees per 0.04 ha plot. Results from this study will help guide wildlife managers, urban planners and landscape designers who require specific information such as how many trees are necessary within an urban management project to help improve the suitability of urban forests for birds.