Habitat selection and demography of mixed-grass prairie songbirds in a fragmented landscape

The overall aim of my thesis was to (1) determine whether the effects of patch size on habitat selection and demography of mixed-grass prairie songbirds is similar to that documented for songbirds in forest and tallgrass prairie habitats, and (2) to identify nest site selection patterns, and (3) determine whether nest predation might influence nest-site choice of mixed-grass prairie songbirds.; Sprague's Pipit (Anthus spragueii), Baird's Sparrow (Ammodramus bairdii), Grasshopper Sparrow (A. savannarum ), and Chestnut-collared Longspur (Calcarius ornatus) were all found to be area-sensitive as they were more abundant and/or occurred more frequently in larger patches of grassland habitat. However, the ratio of edge to interior habitat was a better predictor of area-sensitive species than patch size in most cases. Horned Lark (Eremophila alpestris), Savannah Sparrow (Passerculus sandwichensis), Clay-colored Sparrow (Spizella pallida), Western Meadowlark ( Sturnella neglecta), and Brown-headed Cowbird (Molothrus ater) were insensitive to patch size.; My results also show that vegetation structure influences the abundance and nest-site choice of grassland songbirds. Vegetation structure explained additional variation in abundance and occurrence not accounted for by patch size or the ratio of edge to interior habitat. Strong and consistent patterns were found for vegetation variables discriminating nest sites from random sites. However, I found that nest-site vegetation was a weak and inconsistent predictor of depredated and successful nests. Also, vegetation features associated with nest sites were typically not the same variables associated with successful nests, and in many cases vegetation features associated with nest sites were also associated with depredated nests.; Although patch size was a strong predictor of occurrence and abundance for nearly half the species studied, patch size had little influence on nest success. In fact nest success tended to decrease with increasing patch size for five of six species. However, Sprague's Pipit produced more young per successful nest on large pastures. Unlike several studies in forest and tall grass prairie, parasitism by Brown-headed Cowbirds was not related to patch size.; Taken together, my results have important implications for the conservation of grassland songbirds and their habitat in Saskatchewan. While the conservation of large contiguous tracts of habitat is essential to the conservation of area sensitive species such as Sprague's Pipit, small patches of native prairie may also play a vital role in the conservation of grassland birds, particularly small patches with a minimum amount of edge habitat. In addition, management practices that substantially reduce the amount of residual vegetation from the previous growing season(s) will reduce the attractiveness of grassland patches for most mixed-grass prairie songbirds.