Hawks with very long legs

Driving west through South Dakota, surrounded by pasture land and winter-wheat fields, I saw in a grove of trees far from the road what looked like a large nest. Sure enough. Binoculars revealed a stick nest and a large bird standing atop it. "Hawk nest," I told Jude, my wife and birding companion. She focused her glasses on the tree. "Big bird." I said as three more wheeled into view from behind the trees. "Hey, three more. Must be Red-tails." Everything said hawk -- size, stick nest, and particularly the prairie location. "They're Great Blue Herons," Jude said. And sure enough, as she spoke they magically turned into herons. I could see the lazy wing beats, the long legs, trailing legs on the birds in flight, long legs on the bird standing. Until that moment, however, they were hawks because that's what I expected them to be, so that's what I bent information to create. When birding we often see what we think we see.