“Come on, now,” Crowe says. The zookeeper grabs a fistful of grass and tosses it into the air. This is Crowe’s sexiest move — a sly reference to building a nest together. Walnut looks up, curiosity glinting in her marigold eyes, but then she returns to probing the soft, wet ground with her bark-colored bill. She’s simply not feeling romantic, and who can blame her? I’m watching the two of them from behind a van. With binoculars. The bird must be totally creeped out.

“Try getting in the van,” Crowe calls to me. I follow his suggestion, and, almost immediately, Walnut starts responding to Crowe’s overtures. She returns his bows and then turns away from him and holds her wings loosely away from her body. Kneeling behind the bird, Crowe rests a hand gently on her back. Then he starts rubbing her thighs, rhythmically, almost pornographically. Thirty seconds elapse — it feels much longer — before Walnut steps away from Crowe, fixes a few out-of-place feathers, and then stretches out her wings, asking for another go-round.

In past years, Crowe would have taken this opportunity to inject Walnut with a syringe of crane semen. Alas, a matchmaker in Memphis — the keeper of the white-naped crane studbook, whose job is to ensure a genetically diverse captive population — has decreed that they don’t need any more babies from Walnut, at least not this year.