Avian point counts were conducted in tall-grass prairie fragments and adjacent grassland and agricultural matrix habitat in southern Manitoba. Bird density/abundance was compared between habitat types, while variables within prairie at local, patch or landscape level were modeled to determin avian habitat selection. Prairies and matrix grassland habitat supported the same number of species in both years, and densities of all focal bird species were the same in non-native grasslands as compared with native tall-grass prairies. Overall species richness in tall-grass prairies was mainly driven by vegetation variables. Variable responses to habitat structure and composition between avian species indicate that managing grasslands to promote heterogeneity is important to sustain a diverse assemblage of avian species. As individual species were affected most strongly by vegetation structure and richness, it follows that management of prairie vegetation through techniques such as grazing and prescribed burning could optimize habitat usability for birds.

Avian point counts were conducted in tall-grass prairie fragments and adjacent grassland and agricultural matrix habitat in southern Manitoba. Bird density/abundance was compared between habitat types, while variables within prairie at local, patch or landscape level were modeled to determin avian habitat selection. Prairies and matrix grassland habitat supported the same number of species in both years, and densities of all focal bird species were the same in non-native grasslands as compared with native tall-grass prairies. Overall species richness in tall-grass prairies was mainly driven by vegetation variables. Variable responses to habitat structure and composition between avian species indicate that managing grasslands to promote heterogeneity is important to sustain a diverse assemblage of avian species. As individual species were affected most strongly by vegetation structure and richness, it follows that management of prairie vegetation through techniques such as grazing and prescribed burning could optimize habitat usability for birds.

I investigated how orchid biology, floral morphology, and diversity of surrounding floral and pollinator communities affected reproductive success and hybridization of Cypripedium candidum and C. parviflorum. Floral dimensions, including pollinator exit routes were smallest in C. candidum, largest in C. parviflorum, with hybrids intermediate and overlapping with both. This pattern was mirrored in the number of insect visitors, fruit set, and seed set. Exit route size seemed to restrict potential pollinators to a subset of visiting insects, which is consistent with reports from other rewardless orchids. Overlap among orchid taxa in morphology, pollinators, flowering phenology, and spatial distribution, may affect the frequency and direction of pollen transfer and hybridization. The composition and abundance of co-flowering rewarding plants seems to be important for maintaining pollinators in orchid populations. Comparisons with orchid fruit set indicated that individual co-flowering species may be facilitators or competitors for pollinator attention, affecting orchid reproductive success.

I investigated how orchid biology, floral morphology, and diversity of surrounding floral and pollinator communities affected reproductive success and hybridization of Cypripedium candidum and C. parviflorum. Floral dimensions, including pollinator exit routes were smallest in C. candidum, largest in C. parviflorum, with hybrids intermediate and overlapping with both. This pattern was mirrored in the number of insect visitors, fruit set, and seed set. Exit route size seemed to restrict potential pollinators to a subset of visiting insects, which is consistent with reports from other rewardless orchids. Overlap among orchid taxa in morphology, pollinators, flowering phenology, and spatial distribution, may affect the frequency and direction of pollen transfer and hybridization. The composition and abundance of co-flowering rewarding plants seems to be important for maintaining pollinators in orchid populations. Comparisons with orchid fruit set indicated that individual co-flowering species may be facilitators or competitors for pollinator attention, affecting orchid reproductive success.

Area sensitivity of North American grassland birds is a significant conservation concern; yet, its causes are not known. I used point count data from 20 tall-grass prairie patches in Southern Manitoba to assess the relative importance of patch size, edge proximity, and landscape composition on the densities and species richness of grassland songbirds. The degree to which the landscape surrounding point count plots was open, as opposed to forested or urban, had a positive effect on species richness and the densities of most focal species, and was more important than patch size, edge proximity, or habitat amount. These results suggest that landscape openness, not patch size (with which it is usually correlated) drives area sensitivity. Small grassland patches embedded in open landscapes are less susceptible to area sensitivity and may be of high conservation value for grassland birds. / February 2017