Master of Science, The Ohio State University, 2013, Environment and Natural Resources

Increases in urbanization with a growing global population can result in diverse threats to wildlife, including exposure to harmful contaminants. Among environmental contaminants hazardous to humans and wildlife, mercury is of special concern due to its prevalence, mobility in aquatic systems, and persistence in sediments. Aquatic systems, in particular, can have high amounts of mercury in its bioavailable form, which can bioaccumulate in insects and transfer to terrestrial food webs (i.e., to aerial insectivores). Such contaminant flux from aquatic to terrestrial systems is expected to disproportionately affect species reliant upon aquatic emergent insects. To understand the pathways of contaminant flux and their role in reproductive success, I addressed two questions: (1) Is avian exposure to contaminants influenced by territory placement? and (2) Do contaminant loads negatively impact condition and reproductive success? From April-August 2011-2012 I tracked reproductive success of Acadian flycatchers (Empidonax virescens) in 19 riparian forest fragments located across a land-use gradient in central Ohio, USA. I collected blood samples from adult (n = 76) and nestling (n = 17) flycatchers and samples from riparian systems (sediment, aquatic emergent insect, and water) to examine relationships between landscape factors and contaminant concentrations. I used reproductive data and flycatcher contaminant loads to evaluate mercury's impact on productivity and condition of adult flycatchers. Factors most responsible for contaminant transfer to flycatchers remain unclear. Landscape factors, including proximity of territories to rivers, and urbanization surrounding forest sites, were not related to mercury levels in flycatchers, sediment, water, or insects. However, when separately analyzed, I detected a positive relationship between mercury in flycatchers and sediments in urban landscapes, and an opposite, negative relationship, in rural landscapes. Unlike previous re (open full item for complete abstract)

Committee: Amanda Rodewald (Advisor); Mažeika Sullivan (Advisor); Roman Lanno (Committee Member) Subjects: Toxicology; Wildlife Management

Doctor of Philosophy, The Ohio State University, 2008, Natural Resources

Effective conservation of biodiversity in urban areas ultimately requires that ecologists understand both the patterns and mechanisms of urban-associated influences on native plant and animal communities. A neglected consequence of urbanization is the seasonal timing of life cycle events, particularly the tendency of many urban birds to breed earlier in the spring than their rural-breeding counterparts. The overall objectives of this dissertation were to (1) describe phenological and biological differences in avian reproduction in urban and rural forests, (2) identify underlying ecological mechanisms responsible for observed patterns, and (3) identify demographic consequences of phenological shifts in reproduction. First I evaluated vegetation phenology and temperature patterns, two potentially important variables influencing bird breeding phenology. There was an overall pattern of advanced phenology (e.g., bud break, leaf elongation) within species in more urban landscapes which might be associated with elevated temperatures in more urban areas. Results suggest that shifts in plant communities along the urbanization gradient, especially the increased dominance of the invasive and exotic Amur honeysuckle (Lonicera maackii) in urban forests, drove the earlier green-up of urban areas. Avian breeding phenology was also influenced by urbanization, although patterns, causes, and consequences differed between my two focal species. The non-migratory Northern Cardinal (Cardinalis cardinalis) nested earlier in urban versus rural sites, a pattern that was best explained by early spring temperatures. Contrary to findings from other studies, early-breeding cardinals apparently received no benefit in terms of survival or reproduction compared to later-breeding pairs. In contrast, the Neotropical migratory, Acadian Flycatcher (Empidonax virescens) arrived and initiated breeding later in the more urban landscapes – a phenological shift that ultimately reduced reproductive produ (open full item for complete abstract)

Committee: Amanda Rodewald (Advisor); Tomas Koontz (Committee Member); Thomas C. Grubb, Jr. (Committee Member) Subjects: Ecology