What a difference a day makes.
Wood Thrush, Nashville Warbler, Yellow-rumped Warbler, and Ovenbird were great to hear this morning in Berwick. My five stolen minutes were just enough to whet my appetite for more. Looking skyward, I saw many birds moving, not as high as I usually see migrants, but when a heron flew over low and against the grain I knew I was seeing today's bonus bird.
It wasn't a great blue. It was a smaller one. I'm inclined to think it was a bittern, but it could have been a large green. How often is either one of those a flyover? In my experience, almost never. Just a reminder to review the books before the mystery bird appears. No matter what, it's hard to be prepared for every interesting thing migration might throw at you.
More advice: Never set your binoculars aside just moments before a mystery bird is going to wing past.