UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item COMMUNICATING IN SOCIAL NETWORKS: EFFECTS OF REVERBERATION ON ACOUSTIC INFORMATION TRANSFER IN THREE SPECIES OF BIRDS(2011) Blumenrath, Sandra; Dooling, Robert J; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In socially and acoustically complex environments the auditory system processes sounds that are distorted, attenuated and additionally masked by biotic and abiotic noise. As a result, spectral and temporal alterations of the sounds may affect the transfer of information between signalers and receivers in networks of conspecifics, increasing detection thresholds and interfering with the discrimination and recognition of sound sources. To this day, much concern has been directed toward anthropogenic noise sources and whether they affect the animals' natural territorial and reproductive behavior and ultimately harm the survival of the species. Not much is known, however, about the potentially synergistic effects of environmentally-induced sound degradation, masking from noise and competing sound signals, and what implications these interactions bear for vocally-mediated exchanges in animals. This dissertation describes a series of comparative, psychophysical experiments in controlled laboratory conditions to investigate the impact of reverberation on the perception of a range of artificial sounds and natural vocalizations in the budgerigar, canary, and zebra finch. Results suggest that even small reverberation effects could be used to gauge different acoustic environments and to locate a sound source but limit the vocally-mediated transfer of important information in social settings, especially when reverberation is paired with noise. Discrimination of similar vocalizations from different individuals is significantly impaired when both reverberation and abiotic noise levels are high, whereas this ability is hardly affected by either of these factors alone. Similarly, high levels of reverberation combined with biotic noise from signaling conspecifics limit the auditory system's ability to parse a complex acoustic scene by segregating signals from multiple individuals. Important interaction effects like these caused by the characteristics of the habitat and species differences in auditory sensitivity therefore can predict whether a given acoustic environment limits communication range or interferes with the detection, discrimination, and recognition of biologically important sounds.Item BIRD COMMUNITY RESPONSE TO CONSERVATION RESERVE PROGRAM HABITAT IN MARYLAND(2010) Blank, Peter Joshua; Dively, Galen P.; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The populations of many bird species in the United States that use early-successional habitats have been substantially declining over the last 40 years. The main reason for these declines is habitat loss. Land enrolled in the U.S. Department of Agriculture's Conservation Reserve Program (CRP) often represents the only uncultivated herbaceous areas on farmland in the mid-Atlantic and therefore may be important habitat for early-successional bird species. CRP filter strips are strips of herbaceous vegetation that are planted along agricultural field margins and are usually planted with native warm-season grasses or introduced cool-season grasses. We studied the breeding and wintering bird use of CRP filter strips adjacent to wooded edges in Maryland from 2004-2007. We conducted bird and vegetation surveys in filter strips and measured landscape attributes around CRP plantings. We used 5 bird community metrics (total bird density, species richness, scrub-shrub bird density, grassland bird density, and total avian conservation value), species-specific densities and abundances, nest densities, and nest survival estimates to assess the habitat value of filter strips for birds. Bird community metrics were greater in filter strips than in field margins without filter strips, but did not differ between cool-season and warm-season grass filter strips. Most breeding bird community metrics were negatively related to the percent cover of orchardgrass (Dactylis glomerata). Several grassland birds were more common in wide filter strips (>60 m) compared to narrower filter strips (<30 m). The density of early-successional bird species was greater in filter strips with higher plant species richness and shorter and less dense grasses. Wintering bird use was significantly less in filter strips mowed in the fall than in unmowed filter strips. The abundance of northern bobwhite (Colinus virginianus), an important game bird and species of conservation concern, was positively associated with the percent cover of CRP land in the surrounding landscape. These results suggest that the CRP has created additional habitat for many early-successional bird species, but changes in the planning and management of CRP plantings may improve their habitat value for breeding and wintering birds.Item MATRIX EFFECTS ON INDIVIDUAL AND COMMUNITY-LEVEL RESPONSES OF BIRDS TO FOREST FRAGMENTATION IN JAMAICA(2009) KENNEDY, CHRISTINA MARIE; Neel, Maile C; Fagan, William F; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Land cover between habitat patches ("matrix") can impact species persistence in fragmented landscapes by altering resource availability, edge effects, or inter-patch movement. This thesis examines how the matrix affects the Neotropical bird community in central Jamaica in landscapes where forest is embedded in three human-dominated matrix types (agriculture, peri-urban development, and bauxite mining) and one natural "matrix" (continuous forest). First, I examine whether richness, community composition, and abundances of resident birds differ in ~100 forest patches within the four matrix types, and relate species responses to traits influencing dispersal, resource acquisition, and/or population growth. Agricultural landscapes were found to retain avian diversity and community assemblages most similar to intact forest relative to peri-urban and bauxite landscapes. Traits related to resource acquisition best predicted species responses, indicating that resource limitation driven by the matrix may be a primary factor driving bird responses to fragmentation. Next, I determine the relative influence of patch area, isolation, vegetation structure, and matrix type on the occupancy dynamics of resident insectivorous birds. Within-patch vegetation and matrix type were the most important determinants of colonization and extinction, but the effects of patch area, isolation, and vegetation on occupancy dynamics were matrix- and species-dependent. Across the community, the matrix influenced extinction probabilities more than colonization, indicating that extinction processes likely drive population dynamics. Finally, I examine the relative permeability of peri-urban, bauxite, and forested landscapes on the movement of the migrant American Redstart (Setophaga ruticilla) and the resident Jamaican Tody (Todus todus) by experimentally translocating > 140 birds 0.6-4 km from their territories across landscape treatments. Redstarts returned with greater success and faster speed than Todies. Return success was not impacted by landscape treatment, but both species returned more rapidly in forest relative to bauxite matrix, with return times intermediate in a peri-urban matrix. These findings indicate that bird mobility in fragmented landscapes is mediated by the landscape matrix. This research is among few empirical studies to discern the impacts of different matrix types on species patterns and processes. These results inform theory on fragmentation as well as bird conservation in an understudied system.