<p> I estimated patterns of shorebird abundance and species diversity in the Colorado River Delta and Upper Gulf of California wetlands in order to determine the relative contribution of intertidal wetlands and non-tidal anthropogenic wetlands to support shorebird habitat use. Species richness varied from 15 to 26 species among sites and 29 species were detected across sites. Density during the peak migration month was higher at the anthropogenic wetland Cienega de Santa Clara (mean = 168 ind/ha, 95% C.I. 29-367), and the intertidal Golfo de Santa Clara (mean = 153 ind/ha, 95% C.I. 17-323). Anthropogenic wetlands (playa and lagoons) supported high abundance of shorebirds along with intertidal wetlands in the Colorado River Delta (mudflats). In contrast, intertidal wetlands farther south on the Sonoran Coast presented lower abundance but higher diversity of shorebird, likely as a result of the higher diversity of habitats (rocky shore, sandy beach, estuary). I modeled water management scenarios for the Cienega in order to determine the response of the dominant vegetation (southern cattail, <i>Typha domingensis</i> Pers.) and the area of the outflow pool below the marsh to different scenarios of water management. The model indicates that if the inflow rate is reduced below the current 4-5 m³ s^-1 the vegetated area of the Cienega that supports habitat for marsh birds would decrease in proportion, as would the area of the outflow pool in the Santa Clara Slough identified previously as shorebird habitat. Increases in salinity will also reduce the vegetated area due to the low salt tolerance of <i>T. domingensis</i>. In winter about 90% of inflow water exits the Cienega into the Santa Clara Slough due to low evapotranspiration contributing to inundate areas that are used by wintering and migrating shorebirds. Lastly, I explored the feasibility of using Vegetation Indices (NDVI and EVI) to model Yuma Clapper Rail detections in the Cienega de Santa Clara as well as the effects of adding other habitat variables and the presence of fire events in the performance of linear models based on NDVI. Both NDVI and EVI were positively related to the Yuma Clapper Rail detections. The relationship was weak to moderate, but significant (P &lt; 0.001), which suggests other factors besides the vegetation condition play an important role in the bird distribution pattern. A model including all the variability among years was a better predictor of the rails detected per transect, than models for fire and non-fire years. We did not find a significant effect from adding habitat features (water % or vegetation %), and we recommend to include variables at both microhabitat level and landscape level, relevant before and during the breeding season in order to increase the explanatory power of models.</p>

<p> Abstract not available.</p>

<p> Habitat fragmentation and loss is the primary driver of mammalian carnivore extinctions across the world. In the Santa Cruz Mountains of California, native carnivores navigate daily through a landscape highly impacted by human development and activities. The puma (<i>Puma concolor </i>) is the apex predator of this habitat, but it is susceptible to both direct and indirect influences of expanding human populations. Smaller predators are not only affected by anthropogenic disturbances, but also by intraguild competition with the more dominant pumas. </p><p> My dissertation utilizes new technologies to study the ecology and behavior of carnivores in a human dominated environment. In my first chapter, I catalogued puma behaviors in the wild using measurements recorded by accelerometers attached to the animals. I found that I could clearly distinguish movement from non-movement behavior, and that predation events had distinctive accelerometer signatures. The second chapter describes how I used movement data recorded by GPS (Global Positioning System) collars to evaluate puma behavioral responses to increasing development. Pumas primarily traveled nocturnally, and moved more often and further in areas of higher housing development. The increase in activity in human dominated landscapes could have major repercussions on the energetic expenditure of pumas living in fragmented areas. My third chapter addresses the impacts of human development and activities on the entire carnivore community. Combining passive and experimental observations using motion-detecting camera traps, I studied the spatiotemporal behavior of predators across a gradient of human influences. Mesopredator activity was restricted temporally in areas of high human use, and certain predators (e.g., pumas and foxes) were more sensitive to increasing development. </p><p> Lastly, education and outreach is an important component of carnivore conservation. In my fourth chapter, I describe results from a Facebook game I developed with collaborators. Players earned points by identifying wildlife species from camera trap photographs. I found that agreement among players was the most important determinant of accuracy, and that untrained Internet users could identify many wildlife species. The Internet is an emerging tool for outreach, and I hope my work encourages other ecologists to think creatively about incorporating citizen scientists into their research through social media.</p>

<p> Humans introduce non-native plants to new areas at an increasing rate with the increased movement across the globe. These invasive species can become mono-cultures and extremely different from the native floral community. Amphibians, at the same time, are facing global declines with approximately one-third of all amphibians threatened or endangered. Due to the importance of amphibians as prey items for many vertebrates including small birds, mammals, and reptiles, and also predator controls over many invertebrates, including some pest species, the decline of amphibians has large implications for many environments. This study looks at a range of interactions between two invasive plants (<i> Typha angustifolia</i> and <i>Phragmites australis</i>) and two native anurans (<i>Lithobates clamitans</i> and <i>Lithobates catesbeianus</i>). </p><p> As ecosystem engineers, plants form the basis of many communities, and sculpt the physical environment by adding complexity to the earth's surface. They also add chemical constituents either actively or passively too ward off other competitors. This change in the environment on both the chemical and physical level leads to complex possibilities for a changed plant community to impact the rest of the ecosystem, including amphibians. I focus on the physical changes by looking at behavior of amphibians in these invasive plant mono-cultures and non-invaded controls, and their appearance in invaded and non-invaded wetlands, both constructed and naturally occurring. On the chemical side of the matter, I monitor water chemistry measures in natural and constructed wetlands that are either lacking invasive plants or have a substantial presence of these plants, and correlate those measures with tadpole growth and survival. </p>

<p> Despite reductions in species diversity, few studies in wetlands investigate the relationship between biodiversity and ecosystem function (BEF). My research explores the BEF relationship in a recently restored salt marsh in Long Beach, California. I hypothesized that: (1) increasing plant diversity would result in higher primary productivity and decreased recruitment of native salt marsh plants, (2) observed variation in responses would be correlated with species-specific variation in individual demographic parameters, and (3) variation in demographic parameters and resulting ecosystem processes would be correlated with functional traits. I found that while survival over one year was correlated with elevation, overall percent cover and recruit species richness were positively affected by diversity. Performance patterns reveal variation by species in photosynthetic rate, leaf mass per area and chlorophyll a/b ratios. After one year, I found that the overall diversity patterns were driven by selection effect compared to complementarity.</p>

Habitat loss and disturbance due to human activity are major causes of global biodiversity decline. Beyond outright species loss, one potential outcome is modification of species interactions that are integral to ecosystem functioning. To investigate this possibility, I asked whether human activity influences avian frugivory and seed dispersal, bird-fruit interactions that facilitate plant reproduction. On Tobago (West Indies), I compared patterns of frugivory in three adjacent rainforest habitats along a gradient of increasing disturbance: primary forest in a reserve, unprotected intermediate forest outside the reserve, and nearby forest that was moderately disturbed by subsistence resource use. I assessed plant and bird community composition, seedling species, fruit removal, and bird fecal samples, to estimate human effects on seed dispersal and plant recruitment in this ecosystem. Disturbed forest had different species assemblages than primary forest, characterized by more light-demanding plants, more birds, and a shift in the relative abundance of avian feeding guilds: insectivores and frugivores declined, while nectarivores and omnivores increased. Canopy cover declined with disturbance; along with plant abundance, this explained much of the variation in bird species composition. The rate of avian fruit consumption in removal experiments varied considerably but tended to be highest in primary forest. Fecal samples showed that fruit composition of avian diets also varied with disturbance; birds captured in disturbed forest consumed more seeds from light-demanding plants. Seeds in the samples provided evidence of some seed transfer between habitats—from disturbed forest into the reserve and vice versa. Seedling composition was consistent with plant species fruiting in the same study plots, and illustrated some successful recruitment of light-demanding plants in primary forest and shade-tolerant plants in disturbed forest. Notably, the plant community of intermediate forest was more similar to disturbed than primary forest. This suggests that habitat adjacent to areas of human activity can be susceptible to ecological change, even though it does not experience the same direct disturbance. In summary, the unprotected portion of Tobago’s rainforest has a markedly different plant and bird community than the forest reserve, and my results indicate that avian frugivory and seed dispersal can be influenced by moderate human activity.

Thesis (Ph.D.)--University of Western Australia, 2006.

Thesis(M.S.)--Auburn University, 2006. / Abstract. Includes bibliographic references.

Thesis (M.S.)--University of Nevada, Reno, 2007. / "August 2007." Includes bibliographical references (leaves 29-34). Online version available on the World Wide Web.

Thesis (Ph.D.)--Drexel University, 2010. / Includes abstract and vita. Includes bibliographical references (leaves 206-237).