Changing landscapes and resource use by breeding birds in the Mixed Grassland Ecoregion of Saskatchewan

Since 1900, humans have altered the northern Prairies and significantly changed vegetation structure from a grassland (over 85% cover in 1880s) to an agricultural (presently over 65% cover) dominated system. Although previous studies have shown significant alterations to ecological processes at the population and species assemblage levels, few have investigated changes at the broader ecosystem level. This study of the Mixed Grassland Ecoregion of Saskatchewan, Canada investigated changes in breeding bird resources use and regional habitat diversity in relation to broad scale alteration to the landscape. Changes in breeding birds were examined by investigating trends in diversity, migration, breeding bird guilds from the early to late 1900s using historic relative abundances accounts and the Breeding Bird Survey. Vegetation changes created new ecological space that increased both the richness and diversity of breeding birds. Small changes in woodland and wetland area have a disproportional effect on the number of breeding birds that use these habitats. Woodland associated bird guilds increased while those related to wetland habitats declined since 1900. These guild changes are coincident with the changes in vegetation types. The introduction of agriculture has altered resource use on a regional scale by reallocating space and habitat away from grassland and wetland systems. Thus, human agricultural activity has become a major functional component of this prairie ecosystem influencing the type and number and diversity of species. This conclusion suggests that biodiversity measurements alone may be insufficient indicators of ecological integrity and that ecosystem function must be addressed within a context that includes human activities and infrastructures.