If you’ve been looking at the Pennsylvania skies lately, you’ve likely seen them: shimmering, iridescent streaks of blue and white cutting through the air with acrobatic precision. The Tree Swallow (Tachycineta bicolor) is a true marvel of aeronautics, but for most of us backyard birders, they are little more than a high-speed blur. That’s why these shots from felusproductions.com are such a treat. Finding a Tree Swallow willing to model on a branch is like catching lightning