Effects of cattle grazing on the food abundance of prairie bird species in Grasslands National Park, Saskatchewan

Abstract

Grassland bird species have declined dramatically since 1966. This decline can be linked to changes in land use practices, such as grazing. I examined the effects of cattle grazing on the abundance of birds by testing the predictions of the More Individuals Hypothesis (MIH). The study was conducted in Grasslands National Park of Canada (GNPC) in Saskatchewan. Point counts were used to sample richness and relative abundance of birds. I sampled two groups of invertebrates: grasshoppers and carabid beetles. In addition, vegetation measurements were taken to assess the intensity of grazing. I found that (1) grasshopper abundance, richness and diversity were higher in grazed pastures; (2) carabids showed mixed responses to grazing; (3) bird abundance was correlated with carabid abundance, thus supporting the assumptions of the MIH. Overall, my results indicate that grazing can be beneficial for both birds and their invertebrate prey in southern Saskatchewan mixed-grass prairies.