A BIRD-WATCHER is a kind of pious predator. To see a new bird is to capture it, metaphorically, and a rare bird or an F.O.Y. (First of the Year, for the uninitiated) is a kind of trophy. A list of birds seen on a given day is also a form of prayer, a thanksgiving for being alive at a certain time and place. Posting that list online is a 21st-century form of a votive offering. It’s unclear what deity presides.

There was prestige in knowing birds in ancient Rome, and there is prestige today. There are also competitive insect enthusiasts and tree connoisseurs and fungus aficionados, but they lack the cultural stature and sheer numbers of bird-watchers. There are 5.8 million bird-watchers in the United States, slightly more than the number of Americans in book clubs or residents of Wisconsin. That’s a huge army of primitive hunter-mystics decked out in sturdy hiking boots and nylon rain gear, consulting their smartphones to identify or imitate a particular quarry.

There is nothing especially new about them except for their gear. Two hundred years ago the heartland teemed with second sons of wealthy European families who could have stayed home dissipating in traditional style, but chose to go to the New World and find a new animal instead. Reporting your sightings to the Audubon Society is decidedly less glamorous than dispatching a new specimen to a museum in Paris or London, but it’s a kindred enterprise.

Today’s birders are not exploring new territory geographically, as the early naturalists did; rather, they are contouring the frontiers of climate change. It’s April, and the kitchen-window bird observer is limbering up, too. Are the birds nesting early, nesting late? (Do they know something we don’t?) The reporting such observers do is crucial.