On a cloudy September morning in Prospect Park, a massive swath of greenery amid Brooklyn’s concrete sprawl, the fall migrants are flying fast and furious. A group of birders spin excitedly in a clearing, calling out as new species appear. “What a hotspot,” says Valentina Alaasam as she scribbles down each name in rapid succession: American Redstart, Scarlet Tanager, Black-and-white Warbler. Alaasam will add the morning’s counts to a biodiversity database that she and her colleagues at New York University have been compiling for more than a year. The goal: to figure out whether parks in richer areas are also richer in wildlife. “I’ve always been really interested in this concept of luxury effects, where neighborhoods that are wealthier tend to get more investment from the city, and more trees, and more green spaces,” Alaasam says. To test how that may play out in New York, the team has been counting birds, bugs, frogs, and more across 11 city parks, including...