Factors influencing the diversity and abundance of grassland birds in the Waterton Foothills Parkland, Alberta, Canada

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Date
2024-08-26
Authors
Moore, Zachary
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Abstract
Grassland birds are among the most imperilled taxa in North America, with declines being primarily associated with the widespread conversion of grasslands for agriculture. However, alteration of existing vegetation communities and the landscape context in which habitats occur can be important factors affecting the use of remaining grassland habitats by birds. The Waterton Foothills Parkland region in southern Alberta, Canada is characterized by complex topography consisting of native grassland-forest-wetland mosaics. In this thesis, I used naturally occurring landscape heterogeneity and management-relevant habitat metrics to evaluate multi-scale ecological responses of grassland birds. I evaluated how the presence, abundance, and diversity of grassland birds responded to their habitat using Autonomous Recording Units, in-field vegetation surveys, and spatial landscape assessments. I found that the grassland bird community mostly responded to grassland fragmentation and topography within 400 to 800 m extents. Fragmentation increased the total diversity of grassland birds because spillover of facultative grassland birds at edges was greater than decreases in the diversity of a limited pool of obligate species in more fragmented landscapes. Sites with more rugged terrain was autocorrelated with native grasslands, suggesting that landscape-scale responses of grassland birds to terrain ruggedness were associated with the distribution of different grassland types. Local measures of grassland type represented by the percent composition of non-native species and rangeland health were key determinants of the grassland bird community. Healthy, native grasslands supported higher abundances of Vesper and Clay-coloured Sparrows and unhealthy, modified grasslands supported more Savannah Sparrows and Western Meadowlarks. This research supports that sections and quarter-sections of land are informative units for examining the abundance and diversity of grassland birds in the Waterton Foothills Parkland based on responses of the grassland community to grassland fragmentation, topography, non-native vegetation invasion, and range health.
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Grasslands, Birds, Landscape Ecology, Heterogeneity, Grazing, Vegetation Structure, Non-native Species
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