SUMMER AVIAN COMMUNITY STRUCTURE RESPONSE TO HABITAT AND LANDSCAPE VARIABLES AT MATADOR WILDLIFE MANAGEMENT AREA
Romo, Steven Alexander
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Birds are important components of natural ecosystems worldwide and aside from the many ecological services they provide they are also important in human recreation such as birding and hunting. Scientists have used surveys of bird species to monitor the health and functionality of several ecosystems. In North America, one of the most threatened ecosystems is the Great Plains. The prairie habitats within the Great Plains are threatened by numerous land use practices such as urbanization, tree planting by man, conversion to cropland, introduction of exotic grasses, over-grazing, fire control and subsequent woody encroachment. Reflecting the decline of North American grasslands is the decline in grassland bird populations. Knopf (1994) described grassland bird populations as showing the fastest, consistent, and widespread decline of any avian guild. During the summer of 2017 I investigated how the structure of bird communities respond to changes in environmental gradients in the Texas Rolling Plains ecoregion. I surveyed birds along line transects at Matador WMA in Cottle Co. Texas. Concurrent with these surveys I collected data on variables related to microhabitat, microclimate, and invertebrate abundance along each transect. I also processed habitat variables at the landscape scale from satellite imagery via GIS programming. I then performed a canonical correspondence analysis on our bird and environmental data to create an ordination biplot. My ordination organized the environmental gradients and species in a way to reveal distinct habitat types and associated bird species. Many bird species fell near the center of the ordination biplot which may indicate a blending of habitat use on the WMA for those species. I performed multiple linear regressions between the top 11 most frequently encountered species and all environmental variables, and between avian community level metrics and all environmental variables. Only five of the frequently-encountered species remained with significant relationships with environmental variables after the multiple linear regressions. For the community level metrics, total bird abundance, Modified Simpson’s Index of Diversity, and species evenness were all significantly influenced by one or more environmental variables. My project, being conducted in northcentral Texas, lends insight to habitat use by a mixture of birds from both eastern and western North American avifaunae coexisting together. My ordination analysis also identifies key components within certain habitats which strongly correlate with certain avian species. Therefore, these environmental variables in particular greatly shape avian communities in the summer at Matador WMA. The information gained from my multivariate ordination and multiple linear regression analyses is useful to habitat managers and wildlife researchers concerned with both game and non-game bird species in the Texas Rolling Plains.