The dark, smudgy streaks on Xavi Bou's photographs suggest the jerky ink tracks created by a malfunctioning printer, but they actually record the various patterns birds trace while flying in flocks.

Swift bird in flight with a colorful sky in background. Black swallow. Image with copy space.© Marco Lissoni/Shutterstock.com Of all the marvels of the natural world, few are as astonishing as the ...