Oriental and Common Cuckoos are a nightmare for nesting songbirds. Instead of raising their own chicks, these brood parasites sneak their eggs into other species’ nests. When the cuckoo eggs hatch—and they’re adapted to hatch first—the newborns use their first breaths of life to shove the native eggs out of the nest, leaving more space and food for themselves. It’s one part clever, one part insidious. For years, these cuckoos have kept to Eurasia, where native birds have learned to defend themselves against the brood parasites over thousands of years. But now, some scientists are concerned that they might soon colonize Alaska, where local songbirds are utterly clueless to the parasites’ deceptive ways, according to a new study in the Journal of Field Ornithology. “North American birds have absolutely no defense,” says Vladimir Dinets, a biologist at Okinawa Institute of Science and Technology and the study’s lead author, who’s been researching this...