IF BIRDS LEFT tracks in the sky, what would they look like?
For years Barcelona-based photographer Xavi Bou has been fascinated by this question. Just as a sinuous impression appears when a snake slides across sand, he imagined, so must a pattern form in the wake of a flying bird. But of course birds in flight leave no trace—at least none visible to the naked eye. Bou, now 38, spent the past five years trying to capture the elusive contours drawn by birds in motion, or, as he says, “to make visible the invisible.”