Fall Bird Diversity Survey by Forest Type
This was a group presentation created by Liron Gertsman, Hadi Hassan, Rebecca Kuzek, and me for our BIOL 427 (Ornithology and Herpetology) class, uploaded with all group members’ approval.
We compared the species diversity and similarity of birds in Pacific Spirit Regional Park between three sites that represented different forest types: Coniferous, Deciduous, and Mixed. Based on the intermediate disturbance hypothesis, we hypothesized that the mixed site would contain the highest diversity, followed by deciduous, and lastly coniferous forests. We also hypothesized that the species composition of the coniferous and deciduous forests would be the least similar.
Our sampling consisted of three 10-minute point count surveys spaced roughly 125 meters apart for each site. Each site was sampled once a week starting at 10:30 am over the course of 4 weeks (from Oct. 13 to Nov. 5, 2021). Observations were mainly recorded based on bird call identification, but also included visual observation with binoculars when applicable. During our sampling, we also recorded weather conditions and other possible disturbances including the presence of hikers and their pets. We limited inter-observer bias by surveying in alternating pairs, so that each person visits the same site twice.
Simpson’s diversity index was highest in the deciduous site (85.7%), followed by coniferous (77.1%) and mixed (75.1%). In terms of the number of species observed, the deciduous site also had the highest diversity (18 species), while the coniferous and mixed sites were the same (13 species). Additionally, the deciduous site had the highest number of species unique to the site.
Based on Renkonen’s index, species compositions between the coniferous and mixed sites were the most similar (78.5%), whereas the coniferous and deciduous sites were the least similar (25.8%).
Our results supported our hypothesis on the species similarity between sites, but did not agree with our hypothesis on the levels of diversity between sites. Though we found that the presence of dogs and people in the area did not impact the number of birds observed, rain intensity, detectability bias due to the different foliage densities between habitats, and random chance of encountering certain species likely impacted our results.