Avian and vegetation community response to coastal prairie restoration

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2021-05

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Abstract

The data presented in this thesis was conducted on the Welder Wildlife Refuge in San Patricio County Texas during the summers of 2018, 2019, and 2020. The focus of this study was the effects that coastal prairie restoration techniques would have on the avian and vegetation communities as well as certain aspects of Greater Roadrunner (Geococcyx californianus) ecology. Different habitat restoration efforts have been conducted on prairies with varying degrees of success across the United States, but few restoration attempts have been conducted on the coastal prairie, a native tallgrass prairie that originally extended along the coast of Texas through Louisiana. In 2018 I initiated this current follow-up study to assess the progressive temporal changes in the vegetation community on herbicide treated plot in 2014, and the influence of the added treatment of a prescribed burn applied during August of 2019 in reestablishing a coastal prairie grassland. I conducted vegetation sampling along a 30-meter transect in June-July of 2018, 2019, and 2020 at 29 sample points each within both the control and treatment plots. I found that woody vegetation canopy communities varied by plot and herbaceous cover community was most impacted by the application of prescribed fire. The results from the two-way repeated measures analysis of variance show that herbicide application in conjunction with prescribed fire can be a successful in reducing woody vegetation canopy cover while increasing native graminoid cover. When assessing the avian communities found on a control plot and an herbicide and prescribed fire treated plot, I found alpha diversity was highest within the control plot this contrasted with beta diversity which was highest on the treatment plot. Detections of birds in the scrub habitat guild was highest in the control plot in contrast to the treatment plot where the grassland habitat guild had the highest number of detections excluding the arrival of Marsh/Shoreline birds in 2018 due to localized flooding. Northern Cardinals which belong to the scrub habitat guild had the highest density estimates in the control plot. This contrasts with the treatment where Dickcissels which belong to the grassland habitat guild had the highest density estimates. Avian community structure varied in response to woody vegetation canopy cover and graminoid cover. The reduction in brush cover comes with an increase in forage production. Increased forage production will allow for higher stocking rates and ultimately a larger profit if the land manager decides to stock cattle. The Greater Roadrunner (Geococcyx californianus) is a cursorial predator that requires a combination of open areas for foraging and brush for perches and nesting. Little quantitative data are available for Greater Roadrunner habitat selection, especially in coastal prairies and brushlands of the Gulf Coast. I assessed how coastal prairie restoration efforts on the Welder Wildlife Refuge, in San Patricio County, Texas, may influence roadrunners by quantifying home range and habitat selection on the refuge. Our goal is to understand how prairie restoration efforts can contribute toward grassland bird community recovery, while also accounting for species, such as the Greater Roadrunner, that require a mixture of vegetation communities. I used VHF transmitters to determine breeding season home range size and estimate habitat use for 19 Greater Roadrunners in 2018—2020. I examined home range and habitat selection using program LOAS, the adehabitatHS package in program R, and remote sensing data. Greater Roadrunners had a mean home range of 39 ha and a core area of 7 ha. Selection ratios indicate that Greater Roadrunners selected for bare ground and avoided riparian and water landcover types at the 1st order. At the 2nd order, roadrunners selected for bare ground and avoided riparian and water land cover types. For the 3rd order they used all land cover types proportionally with the exception of the water land cover type which they avoided. The removal of woody vegetation may benefit roadrunners on the Welder Wildlife Refuge considering that at the first and second order roadrunners are selecting for bare ground.

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Keywords

Coastal Prairie Restoration, Vegetation Community, Avian Community, Greater Roadrunner

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