Carole & I were standing out on the deck a couple of evenings ago. The deck faces the river, though the water is mostly screened by trees. We're deep in the woods here, so we have lots of birds & the jays have been active lately, calling & rattling around in the trees, but there seemed to be even more activity than usual. In a period of ten minutes, we saw at least a hundred jays fly from the maples by the river, over the house, to the pines by the road & then into the deeper woods. Clearly, we were witnessing the jays' fall migration from the higher mountains down to our foothills. At least some of them will hang around all winter. Here are some historical accounts of such migrations going back to the 19th century from Life Histories of North American Birds.