Long-term population data on birds can provide information on population trends, particularly for species of concern, but it can also provide information on ecosystem structure and function. Monitoring grassland birds is an effective method for assessing the condition of grassland ecosystems, which are amongst the most dynamic ecosystems in Canada. Grassland ecosystems include ecoregions such as bunchgrass, tall-grass prairies and shrubland, but also open forests such as open ponderosa pine and interior Douglas-fir forests. Grassland ecosystems are maintained by fire and grazing, and are threatened by tree encroachment, intensive agriculture, invasive species, use of pesticides, climate change and overgrazing and trampling by cattle.