A recent trip to Mauritius, land of the dodo, reminded me of island birds’ special place in the panoply of bird diversity. But birds of islands are acutely vulnerable to human threats, including climate change.

Like mini laboratories for evolutionary experiments, oceanic islands are where nature tries onunorthodox avian strategies. Take gigantism, which produced the oversize pigeon that was the dodo, and Madagascar’s elephant birds, the largest of their time. Or take fl...