A multivariate analysis of bird species composition and abundance between crop types and seasons in southern Ontario, Canada

Abstract

Many farmland bird species are declining in North America and Europe, yet there are few data documenting bird use of agricultural landscapes, especially in Canada. This information is needed in order to identify candidate factors contributing to declines. We examined the influence of crop type and adjacent habitat on birds in fields of four crop types in three southern Ontario counties during the 1988 breeding (May-July) and 1987 and 1988 migration (August-September) seasons, using canonical correspondence analysis (CCA). Crops included apple Malus spp. orchards in Norfolk, soybeans Glycine max in Essex, vineyards Vitae spp. in Niagara and corn Zea mays (maize) in all three counties. Bird assemblages differed between counties because corn in Norfolk had more adjacent wetlands and woodlands than those in Essex. During the breeding season (1988), significant habitat variables explaining variation in bird assemblages (in order of importance) were adjacent apple orchards, wetlands, and “other” wooded habitats and apple as the crop (as distinct from adjacent apple orchards). During migration, apple as the crop was most important, followed by crop type corn (distinct from adjacent corn), adjacent wetlands and adjacent other crops in 1988. Apple as the crop was most important, followed by grape as the crop (distinct from adjacent vineyards) and wetlands in 1987. Based on median vector distances in ordination space as a measure of the difference between breeding and migration periods, bird assemblages in soybean and corn in Essex changed most, while birds assemblages in apple orchards changed least, although differences were not significant among crops. Our results emphasize the importance of non-crop and crop habitats for birds during both breeding and migration seasons.