I wonder sometimes which they consider "home". Is it the Great Valley of California where they spend the winter, thriving on the grains and grasses that grow all year? Or is it their breeding grounds across the northern tier states or farther north in the Arctic (see their complicated range in the map below from Birds of North America). The answer, from their point of view, is pointless. It's just where life for them happens. One can't go to far with anthropomorphizing birds like I'm doing here.
Still, I sense a disturbance in the force as I've watched them the last few weeks. They know they are going to be leaving soon. I don't know what signals the moment to leave...the angle of the sun in the sky? The temperature? If it is temperature, they are a little bit confused right now. A week or two back it was as warm as April, but the end of February brought freezing temperatures. But in any case, they'll be heading north soon.