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I have now completed around half of my point count surveys within the Burnaby Lake Regional Park area in an effort to measure bird species presence and abundance along an urbanized gradient (Site 1 – Urbanized Area, Site 2 – Moderately Urbanized Area, Site 3 – Naturalized Area).
To date, I have completed 4 replicate point count surveys in each of three areas (2 replicate locations per area, on 2 different dates). I will complete at least one more day of data collection, with 2 more replicate point count surveys in each of the three areas over the next week. Since revising my research design as highlighted in Blog Post 5 I have had no issues in implementing it. Performing surveys between dawn and 10:00am has resulted in a high level of bird detectability. In addition, limiting the number of point count surveys to two per habitat has also made the surveys manageable as it still takes about 1 hour to complete all 6 point count surveys across the three areas on any given sampling day. Overall, the switch to Burnaby Lake Regional Park and the revised hypothesis seems to be going very well and this was a good decision to make sooner rather than later in the research project.
I calculated my explanatory variables for each area (approximately 300m x 300m area) as a whole using aerial photography to determine the percent cover of natural habitat (forest, wetland, etc…) and anthropogenic habitat (buildings, roads, trails, etc…). I used a systematic sampling strategy to place my point count survey sites within each survey area randomly along the road or trail that runs through them. A random number generator provided the first survey point location in each site, while the second survey point was systematically placed 200m away to maintain the minimum distance required for independence between sites. At each point count survey all birds seen and heard within a 50m radius of the observation point were recorded during a 5-minute period.
Looking at the data quickly some ancillary patterns reveal that the species richness is lowest in the most urbanized area but further analysis will be required to determine whether species richness is highest in the moderately urbanized or naturalized area. Bird abundance has been quite high throughout all the sites so it has been hard to determine which site has the highest abundance. Site 1 does have large flocks of rock doves flying through it which will definitely elevate the overall abundance numbers for that site, whereas the other two sites have smaller abundances by individual species but more species overall.
