Crowhugger, yes, I did think probably one reason my bird's shape seemed different from many of the photos and diagrams was not just my angle of view (from below) but the 'posture' of the bird as it flew into the tree and settled into the branches. It had its neck kind of stretched out at first, giving it that sort of sleek, slender look.
Here's pretty much what it looked like as it flew into the tree (except this is a male and I think the one I saw was a female): Red shafted flicker in flight