Ginni Callahan is on a great adventure. She’s sailing the South Pacific in a 36-foot boat with her friend Henrick and two kayaks. She’s enjoying the challenge of photographing and identifying the sea birds they encounter on the voyage.

I started photographing birds on our crossing from Mexico to the South Pacific because looking for them gave me an excuse to stand in the cockpit and stare at the horizon for hours, which was a good antidote to seasickness. Then I realized that photos were great aids for identification. One could zoom in closer with the camera than with the eye. The photo would hold still long enough to study markings against the Seabirds book. The challenges of taking clear photos of a flying bird from a moving boat, with the dynamic background of the sea, kept me trying.

On anchor in the Marquesas I fell in love with the flocks of little white terns and their aerial maneuvers. Sun caught them dancing against a dark background of verdant hillside or gray full-bellied cloud. But I couldn’t get a satisfactory photo.

With the mission of capturing their carefree spirit in pixels, I went ashore with the camera on the atoll of Makemo. That started a tradition of wandering about on scraps of land in the South Pacific and photographing birds, and other things that caught my eye.

Frigates are the ballerinas and the thieves of the sea. They glide for hours on a wingspan that, relative to body size, is greater than any other bird. I’ve watched them harass terns and boobies until they drop their fish, then swoop to catch the falling fish before it hits the water. Still, they are graceful enough to forgive their criminal streak and enjoy watching them.

Among the atolls, there are both great and lesser frigates. Sometimes they soar in mixed flocks of several dozen birds. Males, females, and juveniles of various plumage stages, of both species. To the person who wants to identify them, one flavor from the other, they present a fine challenge. Like the boobies, there seem to be individuals that partially fit the descriptions of one brand and partially the other.

I wonder if they’ve been cross-dressing when nobody’s looking. Swapping feathers. Maybe they’re soaring up there teasing each other. “Hey, you lesser frigate.”

On Makemo, I watched a small group of great frigates looping about the sky. Males, females, and pink-headed juveniles. Some sort of squabble ensued between a female and a youngster. Photos slow them down and catch their ballet. At some stages, the young one appears to be begging for food, then the female turns, chases, and actually chomps on the juvenile’s tail feathers.