For my field research, I investigated whether the presence of spotted towhees (Pipilo maculatus) is influenced by variation in shrub cover within Garry Oak woodlands in Beacon Hill Park, Victoria, B.C. Using a stratified random sampling design, I selected 18 study sites representing a gradient of shrub cover classified as sparse, moderate, or dense based on the number of 1 m² subplots occupied by shrubs within each 5 m x 5 m quadrat. At each site, I conducted standardized 10-minute point count surveys on three separate mornings during the breeding season in June to record towhee presence. The proportion of days each site had towhees present was used as the response variable. My aim was to determine whether dense shrub cover, which is known to provide foraging opportunities and nesting habitat, is associated with increased site use by towhees.
There were a few changes I had to make to my design throughout my research. I took interest initially in the large proportion of the park composed of vulnerable Garry oak ecosystems because I noticed unique patterns of biodiversity here compared to other more polished park areas (e.g., there seemed to be more bird activity and species richness here). First I wanted to investigate the effects of an invasive perennial shrub, scotch broom, on the Garry oak woodlands. But considering Beacon Hill is an urban park with ongoing preservation and management efforts being made to protect sensitive species (including removal of invasive alien species), this didn’t make sense.
I changed my focus to looking at how a component of the habitat structure (shrub cover) in these Garry oak woodlands influences presence of a specific bird species. This was originally the generalist species American Robin (Turdus migratorius). However, I changed my subject to spotted towhees because they have more of a specific habitat preference being ground-foraging and nesting birds known to like shrubby areas. I wanted to investigate whether this pattern was also present in Garry oak ecosystems within an urban park.
Even though I carried out a very simple field research project in comparison to the research papers we’ve looked at in this course, I found it much more difficult and time consuming than I would have thought. I definitely feel like I have a better understanding and appreciation of what goes into ecological research and the process of finding/building evidence to support underlying theories.