Townsend's Warbler

It's not unusual to see Townsend's Warblers in western Oregon in winter, but this year there seems to be a winter invasion that is more typical of northern finches or owls. I haven't heard any explanation for it so far, but if I were to guess, I would say it's because of the bumper crop of spiders we had here last spring and summer, or perhaps climate change has made it unnecessary for them to go to Costa Rica for the winter.