Ecological fields of territorial units are populated by closely related species of birds by complimentary conditions. Their composition is determined by the form and power of contact of their areas with the territory, the stability of the links between them, the variability of the habitat, ecological features, adaptability and species strategy. In the sphere of interaction of these states take place a process of stabilizing communities in an unstable environment. This is reflected in the example of the Anseriformes group.