Quantifying anthropogenic causes of habitat change and its effects on wild bird population dynamics using advanced analytical methods

Humans exert tremendous influence over ecosystems directly and indirectly by transforming terrestrial habitats and altering the population dynamics of wild animals. In this dissertation, I quantified processes hypothesized to link human and wildlife populations through habitat modification and harvest. In chapter 2, I implemented an integrated population model to test covariates including human population density and agricultural land cover in the breeding range on survival rates of adult and juvenile hummingbirds. Human population density strongly negatively influenced survival of rufous hummingbirds (Selasphorus rufus), a Neotropical migratory species of conservation concern. Additionally, I found support for the hypothesis that higher recruitment rates drove population growth in Anna’s hummingbirds (Calypte anna), a non-migratory species undergoing a Northward range expansion. In chapter 3, I tested hypotheses that link human socioeconomics to land cover change in regions in Mexico and Colombia that were previously identified as conservation priorities for Neotropical migrants. Conversion of range land to crops in Mexico suggested agricultural intensification presents a growing threat for Neotropical migrants, whereas in Colombia, deforestation for range land suggests agricultural expansion is a prominent threat. I tested hypotheses concerning the socioeconomic conditions that drive these land use dynamics. Combined with protecting remaining natural forest, land uses that maintain forest cover (e.g., silvopasture or agroforestry) may yield positive conservation outcomes for Neotropical migrants threatened by habitat loss while also meeting the needs of rural communities. In chapter 4, I tested hypotheses linking human socioeconomics to population trends of bird communities directly and indirectly through deforestation. Surprisingly, forest-dependent communities did not decline in response to local deforestation. I speculate that this is because the largest impacts of anthropogenic habitat modification occur in the early stages of habitat change, followed by population stabilization. Conversely, poverty led to population declines for communities used in the wildlife trade and forest protections exacerbated rather than mitigated this impact, highlighting that protected areas do not always buffer socioeconomic pressures and may exacerbate them in certain contexts. Overall, my thesis elucidates the context-specific mechanisms that link humans to wildlife directly and indirectly, driving wildlife population change.