Wherever the wind may blow: albatrosses and frigatebirds spend most of their long lives soaring over the sea. Miniature electronic trackers and sensors are now showing ornithologists where the birds go

Natural History, Oct, 2004 by Henri Weimerskirch

Among oceangoing avian species, albatrosses and frigatebirds are the quintessential seabirds. Both rely entirely on the ocean for food. Their overall shapes, albeit distinct, free them from any dependence on terra firma except when breeding. Each bird is a magnificent flier in its own environment: an albatross can spend between 90 and 5 percent of its life soaring on cold gales over subantarctic seas; a frigatebird can ride warm thermal updrafts over tropical oceans for more than a week at a time without touching down on land or water. And beyond their oceanic habitat and their superb flying skills, the two birds share some distinctive features of life history: they have the lowest rates of reproduction and the latest onset of maturity among all birds. Frigatebirds live for decades, but albatrosses hold the record for seabirds, reaching ages of sixty to seventy years and continuing to reproduce into their fifties.

How did these birds come to have such similar, unusual, life histories? It would be natural to think that the albatrosses (there are between fourteen and twenty species, depending on which ornithologist you agree with) and the frigatebirds (five species) are closely related in evolutionary terms. But they're not. The two groups are members of two well-differentiated evolutionary orders, three major steps up the hierarchy from the species level. But since they're not closely related, what does account for the similarity of life histories? That is a question I've been mulling over for a long time, and one that has been directly guiding my research for several years.

My work on albatrosses, particularly the wandering albatross (Diomedea exulans), began twenty-five years ago, when I was a graduate student studying breeding behavior on small islands in the subantarctic Southern Ocean [see map on next page]. At that time, breeding was the only albatross behavior my colleagues and I could observe closely; back then, biologists had no way of learning much more than, say, an observant sailor could discover about the behavior of albatrosses at sea. But in the intervening two and a half decades, technology has come to the rescue. Thanks to generation after generation of ever-smaller electronic tracking devices, biologists have pierced the veil of obscurity and tracked albatrosses on their amazing foraging journeys. Those excursions can cover vast loops more than 9,000 miles long--as if birds nesting in New York City flew to the shores of Italy to forage and then returned to their nests.

As my colleagues and I began to track albatrosses, the question of why their life histories bore such striking resemblances to those of the frigatebirds was never far from my mind. By 2002, when the new tracking technology had revealed many of the secrets of albatrosses, I knew it was time to apply the same methods to frigatebirds. That work is now paying off. The new packages of miniaturized electronic devices are helping biologists understand in detail the many ways frigatebirds are the tropical counterparts of albatrosses. Out of sight of land or ship, the albatrosses and frigatebirds we have fitted with instruments are demonstrating that, despite the birds' genetic distance, the hard facts of soaring and foraging at sea force even the most disparate lives to converge.

My studies of the wandering albatross have repeatedly taken me to two of the most remote islands in the Southern Ocean, Crozet and Kerguelen, where the birds breed and nest. My usual port of departure is Reunion, a French-administered tropical island in the western Indian Ocean. To reach the breeding grounds takes as long as ten days in a Supply boat on tossing seas, a voyage I've now made eighteen times. But the bird, a graceful wanderer whose white body is offset by narrow wings that can span eleven feet, has always been worth the trip.

The breeding behavior of wandering albatrosses is much like that of the frigatebirds I have studied, but it is anomalous among birds in general. Usually neither group mates before reaching age ten or twelve--what in other birds would be a ripe old age. Females of both groups lay only one egg, and then take their time raising the chick to the fledging, or independent, stage. The wandering albatross tends its young for nine months, the frigatebird for a full twelve--the longest of any bird. Such protracted parental responsibilities leave both groups with little choice but to take at least a year's "sabbatical" between reproductive efforts.

Sailors have always known that albatrosses venture far out to sea. Partly because an albatross could appear with strong winds, sailors would respect it as "the bird/That made the breeze to blow," in the words of Samuel Taylor Coleridge, their best-known bard. (According to legend, albatrosses also carry the souls of mariners lost at sea.)

But where do the avian wanderers go when they are out of sight of land or ships, especially when pressed by the needs of their offspring to make return trips to the nest from the feeding grounds at sea? Where, how, and how often do they encounter their prey--squid, fish, and the remains of dead whales, seals, and penguins--that they partially digest and eventually rigurgiate for their chick? Back in the 1980s, when an albatross would pass our ship, we had no way of knowing where it had come from, where it was going, or whether it was a breeding adult, an immature bird; or a bird on sabbatical.