Flam: If killing one species might save another, should we do it?

It’s routine practice for government officials to kill animals deemed invasive or destructive. For the most part, Americans accept this or look the other way — especially if the “pests” are insects, rodents or garden-munching deer. That’s changed now that the Fish and Wildlife Service plans to shoot thousands of owls in California, Oregon and Washington.

The species on the hit list is the barred owl — a creature whose adaptability has enabled it to spread into new areas. This expansion...