User: | Open Learning Faculty Member:
The theoretical basis for my research project examines how varying levels of urbanization impacts bird species presence and abundance. To examine this I’m collecting data on bird species presence and abundance (response variable) within three areas that represent different levels of urbanization as determined by the percent cover of natural and anthropogenic habitat (explanatory variable).
Based on other research related to bird species presence and abundance along urban gradients (Hartje 2017, Blair 1996) there theoretically should be a difference in the species richness and abundance between sites with different levels of urbanization. More particularly, the most urbanized sites should theoretically have the lowest species richness, and the most natural sites should theoretically have the highest species richness. However, previous studies have not always aligned and some have found that species richness was highest in intermediately disturbed sites (Blair 1996) whereas other studies found species richness highest in the most naturalized sites (Hartje 2017). It will be interesting to see where the results from my research align in this respect. While theoretically abundance should also be highest in more natural sites, previous studies (Blair 1996) found that highly urbanized sites often have the highest overall abundance due to large flocks of a single species. Again, it will be interesting to see how my results compare to the other literature on the topic and if they align with the theoretical perspectives on bird species richness and abundance along urbanized gradients.
It is also important to think about how both species richness, and natural habitat is examined and characterized. Theoretically, species richness includes all species, both native and non-native, but it might be beneficial to tease these categories apart. For example, if an intermediately urbanized site has the highest species richness but hosts exclusively non-native species then its value as bird habitat would likely not be comparable to natural areas where species richness might be lower but is dominated by native bird species. Additionally when classifying habitat it is important to think about the impact native and non-native plant species play. An invasive Himalayan blackberry (Rubus armeniacus) thicket may host similar abundance values as a thicket of native vegetation but the overall species richness will be higher in the native thicket (Astley 2010). As a result, when classifying habitat should blackberry thickets theoretically be categorized as natural or anthropogenic habitat? While I won’t have the ability to examine these issues in my research project their theoretical impact on bird species presence and abundance, and the ways of evaluating overall richness and abundance do provide something to think about and will be mentioned in the final report.
Keywords: urban habitat, urbanization gradient, non-native species, bird species presence and abundance.
