On a stretch of public beach on the shores of Lake Ontario in New York, a tiny shorebird huddles in a hollow of sand, sheltering its eggs from the burning sun. This unassuming bird is a triumph for wildlife conservationists across North America: It’s a Piping Plover. The endangered shorebirds haven’t nested on this beach in more than 30 years—but now they’re back. After years of increased protection and habitat restoration, Piping Plovers are finally recovering from near-extinction throughout North America. The Great Lakes populations had a particularly rough go. Plovers are intensely loyal to their nesting grounds, and the Great Lakes plovers don’t intermingle with Atlantic or Great Plains plovers. That was bad news, as their habitat was especially vulnerable: The wide, sandy beaches where plovers like to nest, rich in tasty invertebrates and convenient camouflage, are also in high human demand in the Great Lakes. When people and plovers compete for shore, people usually...