Why bullfinches fly it for the winter and where to fly in the spring?

Bullfinches - sedentary birds, and not in some distant lands, they do not fly away in the spring. It turns out, bullfinches spend most of their lives in coniferous forests, and in the winter gather in flocks and fly in search of food in the next town. All peeled rowan berry and left without food sparrows, bullfinches voracious fly back. It is also true in the summer in the woods to see the birds is very difficult: they do not cry out loud all the time hiding in the trees.