For Janet Eschenbauch, her daughter-in-law Amber, and their close crew of volunteers, the month of July is so much more than backyard barbecues and beachside frolicking. July means waking up at dawn, piling into a beat-up green Subaru, and rumbling 50 miles into the Wisconsin grasslands. It means spending days peeking into wooden boxes for signs of American Kestrels, banding the birds, and collecting data about North America’s smallest falcons, which have been on an inexplicable decline for the past 50 years. Eschenbauch, who leads Central Wisconsin Kestrel Research, says that in typical years, at least 40 percent of the kestrels they encountered were returners, recognizable by the tiny bands she secured around their legs. “Those were the birds that were going all the way down to Missouri and Mississippi [to winter], and they were coming [back] either to the exact same box or a box half a mile away,” she recalls. “I mean, you could count them. They came back years and years...