This has always been my perception of bird migration in the fall: the days grow short and cool and then, one day, I notice a v-shaped caravan of Canada geese flying southward. Then another and another. Within a few weeks of that first sighting, I hear their melancholy call one final time for the season. Then they, and all the summer birds, are gone. It’s a mass exodus for warmer climes, over and done in the blink of an eye and long before the snow flies.
But what of the geese on the unfrozen mill ponds in January? Or the robins at the birdfeeder in December? It turns out that the process of migration is much longer and less predictable than my cursory observations had led me to believe. First of all, for some species, fall migration begins long before the first ears of corn are ready to be picked. Take, for example, the yellow warbler, whose massive breeding range extends from parts of Mexico to Newfoundland and into Alaska. It is among the earliest songbirds to arrive in the spring and among the first to embark on the return journey. » Continue Reading.