Date Presented

Spring 5-18-2024

Document Type

Thesis

First Advisor

Dr. John Styrsky

Second Advisor

Dr. David Perault

Third Advisor

Dr. Price Blair

Abstract

Aves (birds) is an essential class of animals that contribute to ecosystem function as predators, pollinators, scavengers, seed dispersers, seed predators, and ecosystem engineers. However, Aves, and the roles they fill, are threatened when ecosystems are altered, fragmented, and destroyed by urban expansion. Some bird species can continue to live in urban environments, but many are unable to tolerate habitat loss. Birds’ differing capacities to tolerate urban environments is crucial knowledge that informs conservation efforts, influences which ecosystem services are lost, and determines how species richness and diversity changes. This study analyzed how overall bird diversity responds to urbanization. Additionally it investigated if certain guilds of birds - forest & open woodland species, grassland species, backyard bird species, heavy urbanization species, year round species, and non-breeding species - are affected in different ways by urbanization. I hypothesized that increased urbanization would cause decreases in species diversity and richness as well as losses of ecosystem services. Historical winter bird data from the Christmas Bird Count (CBC), a citizen-science led annual bird census organized by the National Audubon Society, was used to assess changes in bird populations over time. This study analyzed changes in bird diversity in two CBC circles, McKinney, TX and Hagerman National Wildlife Reserve, TX, in five year intervals from 1985 to 2020. Urbanization in these two circles was determined using the United States Geological Survey CONUS Collection 1 data and ArcMap. ANCOVA analyses of species diversity (Hill-Shannon index), total abundance, and number of species observed were conducted for each guild of birds. Urbanization caused diversity trends for the bird group containing all birds observed to progress in significantly different ways. Bird diversity increased in the urban environment (McKinney) and decreased in the natural environment (Hagerman). Trends in the abundance of winter visitor birds were also significantly different as a result of urbanization. The abundance of winter visitor birds increased at a larger rate in the natural environment (Hagerman). Other than these two instances, differing rates of urbanization did not have a significant effect on how species diversity, abundance, and number of species observed changed over time. However, the ways in which urbanization does affect community diversity and abundance emphasizes how crucial the preservation of natural, undisturbed ecosystems are for bird communities.

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