It’s a bird-eat-bird world out there—and Roy Dunn is out to photograph it, even if it’s occasionally hard to watch. A wildlife photographer for more than three decades, he is particularly fond of hummingbirds, since he enjoys the technical challenges of high-speed photography. “I’ve watched hummingbirds for thousands and thousands of hours,” Dunn says. He’s racked up that time both out in the wild and in his California backyard, where he estimates about 150 hummingbirds rely on his nectar feeders during peak summer season. During all that time watching hummingbirds, he occasionally has had some company: a Greater Roadrunner. While Dunn lurked behind his camera, the carnivorous bird, which typically eats lizards and insects, would lurk at the base of a flowering cactus or a hummingbird feeder and wait for a feathery snack to stop by. Then, while the hummingbird is enjoying a sip of nectar—pounce! Even when ambushed, the hummingbird gets away most of the...