At the top of the north mound, Ramírez-Garofalo parked and got out to look around. The grass rose past his hips and swayed in the breeze. He has been studying the return of grasshopper sparrows, eastern meadowlarks, sedge wrens, bobolinks, and other grassland birds to the park for the past decade, since he was a student at the College of Staten Island. Several of these species are considered at risk, and hadn’t been seen living in the city for decades. “Last year, we had a hundred and thirty-six pairs of grasshopper sparrows, which is, like, unheard-of numbers,” he said. In his telling, after years of flying by during annual migrations, these birds have begun to gaze at this section of the outer boroughs with the cool eyes of upwardly mobile young professionals. “They see this habitat and they say, ‘Oh, wow. There’s a lot of food here. It’s damp. The grasses are tall. I could see myself breeding here next year,’ ” he said.