Climate Change Might Be Driving Albatrosses to Divorce

Albatrosses do not fall in love the way humans do.

When the birds couple up, it’s almost always for keeps. Their lives start lonely—albatross parents lay only one egg at a time, and may leave their offspring unattended for days—and at just a few months old, each juvenile embarks on an epic solo voyage at sea. They fly for months and months and months, learning what it is to be a bird. “It can be three years before you see them again,” Francesco Ventura, a bird biologist at the University of Lisbon, told me.

The adolescent albatrosses return to their colony single and ready to mingle. They touch down, find a group of like-minded individuals, and start to dance. At first, “it’s kind of like being at a club,” Melinda Conners, a bird biologist at Stony Brook University, told me. The young hopefuls are seeking a partner that’s both sexy and in sync with their own moves. Some species will sashay and shimmy and shriek; others are more muted, satisfied to simply bow and nod, and click and clack their beaks together. They are all fumbling at first, wee babes at the dating game—exuberant, but “doing it all wrong,” Conners said.

The birds ultimately find their rhythm. Over the years, the mosh pits get smaller, the duets more intimate, until they each stop dancing with all partners but one. This is their perma-mate, their ride or die, their forever bae; once albatrosses unite, they almost never break up. Year after year, albatrosses fly out to sea alone. And year after year, they return to the same partner to breed, sometimes raising dozens of chicks together, until one of the duo dies at the end of a decades-long life. When Ventura and his colleagues visit black-browed-albatross populations in the South Atlantic Falklands, for instance, they regularly tabulate “divorce” rates below 4 percent, sometimes near zero.

That’s true, at least, when times are good. But during certain years, the separations seem to intensify, leaving more birds than usual stranded in the doldrums of singlehood, unable to reproduce. Fluctuating environmental conditions—likely a symptom of climate change—may be the culprit.

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Ventura, who has been watching albatrosses for years, worries about heightened divorce rates, because the birds benefit so much by engaging in ritualized romance. Hatching and rearing chicks, even just one at a time, is difficult work; parents must take turns leaving the nest to forage for food, sometimes for weeks-long stints, while the other remains on the nest, fasting, guarding, waiting. “The whole breeding season is this carefully timed partnership,” Nina Karnovsky, a bird biologist at Pomona College, told me. Enduring bonds translate into better communication, better coordination, even a sort of trust. The two birds entwine their behaviors so intimately that, somehow, after spending most of the year soaring solo above the ocean, they manage to return to the same nesting spot to breed, at almost exactly the same time. The birds will have extra-pair copulations—that is, cheat—but their modus operandi is monogamy. They know to cling to the relationship that counts.

Under typical circumstances, only a handful of couples will ever truly call it quits. When albatross bonds do break, Ventura told me, it’s almost always a strategy the birds use to “correct for suboptimal partnerships” that keep resulting in breeding failures—eggs that never hatch, or chicks that never fledge. Finally fed up, one bird, usually the female, simply peaces out to find better prospects.

If the original dalliance was a dud, many females will improve their reproductive success after they rewed. But while poring over data gathered during the past two decades, Ventura and his colleagues have started to notice a troubling trend. Some of the albatross couples on New Island, in the Falklands, seem to be divorcing unnecessarily, severing their ties even when everything about them seems to mesh. In many cases, Ventura told me, the birds are probably compatible, with many good years and healthy chicks ahead of them. “They should have stayed together,” he told me, and yet, something in the birds’ surroundings is cleaving them apart.

Albatrosses do not divorce the way humans do.

When the birds head for splitsville, they don’t hire lawyers, and no alimony changes hands. Sometimes they squabble; sometimes the break is quite clean. “We still don’t fully understand why divorce happens in birds,” Antica Culina, a behavioral biologist at the Netherlands Institute of Ecology, told me. But the repercussions can reverberate throughout populations, perhaps even species, if the events are frequent enough. “Divorce means they are starting over,” Karnovsky told me. “They have to go through the whole courtship again, the whole energetically expensive display.” For albatrosses, whose couplings can take years to solidify, that can mean stripping away multiple opportunities to reproduce—a real waste, if nothing was wrong with their initial choice.

According to Ventura’s research, that’s what’s happening on New Island in years when food grows scarce. In 2017, for example, albatross divorce rates more than doubled from the average of 3.7 percent, up to 7.7 percent. That year, the local sea surface was unusually hot, which generally spells trouble for food availability—toasty top layers of water just don’t mix as well with the nutrient-rich ones below. The link between ocean temperatures and divorces has become clear since the mid-aughts, when Ventura’s team first started tracking the birds’ matrimonial success: “In resource-poor years, everybody struggles,” Ventura told me.

Some of the splits can likely be traced back to breeding problems, the best-studied trigger of divorce. A few birds might forage so poorly, for instance, that they actually can’t produce viable offspring, or they simply prioritize their own survival over sex. But Culina notes that Ventura’s study, which she wasn’t involved in, shows that problems in the environment can drive divorce in more subtle ways too. Crummy environmental conditions can make it tough for even the strongest, fastest, sexiest birds to chum up with their mate. They might struggle to sync their schedules; they might each have a much shorter fuse. Even females that have been very reproductively successful seem more likely to divorce a partner during these bad stretches. Ventura describes it as a sort of misguided “partner blaming,” wherein the birds confuse bad conditions for bad mates. “It’s kind of crazy to think about,” said Conners, who wasn’t involved in the study. “Some of these pairs have potentially been raising chicks for decades … and they’re being broken up by things that were entirely out of their hands.”

Researchers rarely see the moment of divorce in real time, though even imagining it is bleak. Karnovsky has seen a version of the split in Adélie penguins, which also take alternating shifts on their nest. Left alone too long, birds will grow hungry and impatient; they fidget and call out, as if worried they’ve been abandoned. “It’s like they’re saying, ‘I’m so hungry, I have to go,’” she told me. Eventually, the birds jump ship, leaving their partnership broken, their eggs unguarded.

On New Island, where some 15,500 black-browed-albatross breeding pairs make their home, the population is thriving; Ventura and his colleagues aren’t yet seeing divorce wreak havoc, even in pretty rough years. But they fear that resilience won’t hold for all populations, especially as the years wear on. Albatrosses around the world have long been threatened, by plastic pollution that chokes them, by long-line fishing vessels that snare the birds on hooks and drown them, by invasive rodents that attack their nests. Warming seas are “yet another human-caused impact” that the birds don’t need, Karnovsky said. As climate change accelerates, these home-wrecking effects could be magnified. “I don’t think the birds will have time to adapt,” Stephanie Jenouvrier, a seabird ecologist at Woods Hole Oceanographic Institution who has been independently tracking the impacts of ocean anomalies on birds, told me.

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What may eventually be lost to climate change goes far beyond a potential dip in avian numbers. For the birds, breakups come with a personal cost: the vanishing of one of the most compelling emotional bonds in the animal kingdom. Albatrosses in matrimonial sync will tenderly preen each other and cuddle in their nest. They will nuzzle their heads together, and doze breast to breast. “They just kind of dote on each other,” Conners told me. “You see them absolutely celebrating when a mate returns” from a trip at sea, hopping up and vocalizing. The ties that bind them are strong. But they might not be strong enough to withstand the changes wrought by an ever-warming world.