In agricultural landscapes, hedgerows provide critical habitat for songbirds. Himalayan Blackberry (Rubus armeniacus; HBB) is a widespread invasive species in the Pacific Northwest that has been linked to lower breeding songbird diversity. My study explored two possible explanatory mechanisms: educed structural complexity and lower arthropod abundance as a food source. I conducted avian point counts in 51 hedgerow segments at two locations in the Lower Mainland of British Columbia. In these segments, I quantified vegetation structure using a Foliage Height Diversity (FHD) metric derived from LiDAR data. I sampled arthropod abundance on the foliage of woody understory vegetation. I used multiple regression to identify best fit generalized linear models. Songbird diversity decreased with HBB % cover and increased with FHD. However, arthropod abundance was unrelated to bird metrics, and similar between HBB and other native shrubs. This suggests that hedgerows should be managed to control HBB and maximize vegetation structure., songbird diversity, agricultural landscapes, Himalayan Blackberry, hedgerows, arthropods, LiDAR
Old field is a unnatural habitat that usually occurs as a result of agricultural land abandonment and is the product of early-stage natural succession on a previously managed field. In an agricultural setting with monoculture crops, old fields provide more vegetative complexity through ground cover diversity and shrubs and hedgerows. In Delta, British Columbia, several old-field sites are managed for wildlife and provide nesting habitat for songbirds over the summer, as well as foraging habitat for overwintering raptors during fall and winter months. I surveyed two old-field sites near Boundary Bay, and two field sites at the Vancouver Landfill to compare the influence of old-field vegetation on different bird communities and improve understanding on species using the landfill. I conducted fixed-radius point counts for songbirds, and standing counts for raptors. Comparing replicate field types (n=2) I found that overall diversity of songbirds was higher in old field, and also associated with structural features like shrubs and trees, while abundances of Savannah Sparrows (Passerculus sandwichensis) decreased with proximity to shrubs and trees. My results support the conclusion that installing structural vegetation features at the landfill would maximize breeding songbird diversity. I also found the landfill to support higher diversity of wintering raptor species, but old field supported consistently higher abundances. This suggests that the landfill is currently functioning as lower quality wintering habitat, and that different management techniques should be considered.
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Relationships between changing environmental variables and amphibian populations have been understudied. Yet, alterations to temperature and precipitation have been suggested as contributors to the decline of some pond-breeding species, such as the Oregon Spotted Frog (Rana pretiosa). R. pretiosa has been classified as the most endangered amphibian in Canada, yet the cause for its decline is unknown. Therefore, this paper examined associations between temperature and precipitation, and R. pretiosa population trends, using a 10-year data set from two breeding populations in the
Lower Mainland of British Columbia. Timing of oviposition was positively related to higher temperature and increased precipitation within both populations (p<0.05). No statistical relationship was determined between egg mass productivity and temperature or precipitation; however, this paper proposes that further research, consistent protocols and longer study periods, is necessary in order to determine environmental variables as possible predictors of population success. This paper recommends the evaluation of breeding success through survivorship studies, as such methods provide insight into
productivity as the primary determinant for population recruitment. Further, ecological restoration efforts can be implemented to help ameliorate negative consequences climate change poses on reproductive success., amphibian, climate change, conservation, ecological restoration, endangered, population dynamics, population monitoring, survivorship