Avian communities, because of their potential high diversity, are ideal for studying the response to potential quantity of resources provided by local and regional habitat. Urban neighborhoods vary in types and magnitudes of anthropogenic stressors they experience, resulting in a continuum of anthropogenic disturbance, often referred to as a gradient of urbanization. The aim of this study was to investigate anthropogenic drivers of urban bird communities in three Portland, OR neighborhoods (Hillsdale, Lents, and Pearl). The three major questions of this study were: 1) What are the significant landscape traits that characterize the neighborhoods? 2) Is there evidence that the urban matrix may host similar avian community assemblages as neighborhood green space? And 3) Are landscape characteristics able to predict native bird communities, and if so, what scale is most explanatory?
Neighborhoods were sampled for three months (May - July, 2018) during the breeding season of local birds. Utilizing a community-based approach, parks (n = 17) and neighborhood residential areas (n = 34) were sampled using 50-meter point counts. Community attributes (richness, abundance, and diversity) were compared to landcover (percent canopy, herbaceous and grass, and impervious surface cover), anthropogenic factors (population density and building density), and front-yard vegetative characteristics. Neighborhoods differed in degree of urbanization, with Hilldale being the least urbanized, Lents intermediate, and Pearl the most urbanized. My study found that Portland's urban and suburban avian communities are dominated by relatively few species (13 account for ~98% of observations).
Differences between native avian community attributes were detected by neighborhood but avian communities did not respond strongly to gradient analysis or regression modeling with landcover characteristics. Within neighborhoods, habitat patches had differing levels of native bird diversity. Recreational parks, on average, tended to have lowest bird diversity when compared to residential sites and nature parks. Though few species were represented, avian guilds responded to urban gradients within neighborhoods. Foliage gleaners and insectivores were seen to decrease with increasing urbanization, whereas omnivorous birds increased. This shift in avian guild abundance indicates that species with more specialized traits did less well in more urban areas when compared to generalist species such as omnivores.
| Identifer | oai:union.ndltd.org:pdx.edu/oai:pdxscholar.library.pdx.edu:open_access_etds-6205 |
| Date | 20 August 2019 |
| Creators | Vermeulen, Michael E. |
| Publisher | PDXScholar |
| Source Sets | Portland State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Dissertations and Theses |
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