I live in Eastern Ontario, Canada. But, in the late 1960s through the 1970s I lived in Western Quebec, North-West of Montreal. As a child our crows would leave some time in the fall and were the first sign of spring, returning late February. Their noisy cries would mean March mild spells would soon happen. Where I am presently residing I am a 20 minute drive from my childhood home and the crows here no longer leave to go south. Have you noticed changes in the number of birds migrating south in your research?