Biodiversity Portrait of the St. Lawrence - Biological diversity: Birds

The opposite figure, which was derived from the results of a cluster analysis, reveals the patterns of distribution of the breeding birds of the St. Lawrence. The five main zones, determined from a similarity analysis of adequately sampled squares in the zones, correspond roughly to the main avifaunal regions of the St. Lawrence. These zones comprise five assemblages of species. From upstream to downstream, along the axis of climatic variation corresponding to the latitudinal gradient formed by the river itself, these assemblages include (1) the species in the freshwater wetlands and deciduous forests of the St. Lawrence Lowlands; (2) the species in the estuary and the mixed forests of the Laurentians and Appalachians; (3) marine species and those associated with the boreal (coniferous) forest of the Upper North Shore; (4) species associated with the hemiarctic environment of the Lower North Shore; and (5) species of the Magdalen Islands. The special landscape of the Magdalen Islands and their isolated position in the middle of the southern Gulf explains the uniqueness of these islands ornithologically speaking.

The correspondence between the avifaunal regions and natural provinces suggests that the main bird communities in the St. Lawrence system are structured mainly at this level of generalization. A previous study by Ghanimé et al. (1990) provides an overview of how the avifauna of the St. Lawrence can be subdivided hierarchically into regional subunits, forming 14 relatively homogenous assemblages of bird species.