Last of Season?

Rough-legged Hawk, April 23, 2012

At this time of year I am seeing a FOY (first-of-year) bird almost every day. Saturday it was Purple Martin and Franklin's Gull. Sunday it was Orange-crowned Warbler, and today it was Barn Swallow. As the summer birds replace the winter visitors, I probably also see some last-of-year birds as well. But the trouble with trying to keep track of last-of-year birds is that you never know for sure which one is going to be last. On April 10th I posted on this blog about a Rough-legged Hawk that I thought might be my last of the season. Well, today I saw another one, so I guess I was wrong about the April 10th bird. Who knows? Maybe I'll see even more Rough-legged Hawks before the spring is over.
UPDATE, April 30, 2012: I saw another Rough-legged Hawk today... will this be the last?