In the Falkland Islands, albatross pairs, once a symbol of lifelong commitment, are finding themselves torn apart by longer foraging trips. These were once fixed patterns, and homecomings were celebrated with squawking, the clashing of bills, and even a kind of dance. Now, as ocean temperatures rise and storms intensify, migrations take longer. When one of a pair fails to return home on schedule, the mate may choose another partner.

Among India’s sarus cranes, life has become so hard that the formerly monogamous birds have begun to form trios so they can more effectively raise their chicks.

“For all birds, breeding depends on the availability of nesting sites, nesting material and food. Rising temperatures have affected all three,” says biodiversity researcher and bird conservationist Samad Kottur. “This makes monitoring crucial. We need more studies that focus on the conditions that influence breeding in birds.”

For now, the stresses, often traceable to the impacts of climate change on breeding, are tearing feathered couples apart.

.

Little Penguins

The Bass Strait is typically where Little Penguins fatten up ahead of breeding season, and forage for small fish once they’ve had their chicks.

The waters here are warming fast, however, and food has become scarcer.

Desperate, the tiny penguins (they stand about 1 ft tall) have been observed abandoning their nests on nearby Phillip Island (off the coast of Australia), leaving chicks vulnerable to predators and starvation. As they travel further and further in search of food for themselves and the chicks, they sometimes do not make it back in time.

When a parent discovers that their chick has been allowed to die in this manner, it can call into question the suitability of their mate. This is leading to a rising “divorce” rate, new research has found.

“It’s heartbreaking to see because there will be all these chicks in the colony starving to death,” Richard Reina, head of a Monash conservation research group, told The National Geographic in February, a month after the findings of a 10-year study were published.

The study, conducted by Reina and his team at Monash in association with Phillip Island Nature Parks, found that among the large community of Little Penguins on Phillip Island, divorce rates have begun to fluctuate significantly, ranging from one in 20 pairs to one in three pairs — within the same year.

Divorce rates were lower, the study found, under favourable environmental conditions.

The study was published in the journal Ecology and Evolution.

,

Seychelles warbler

This little bird, typically about 5.5 inches and 6.5 inches across, lives for about 19 years, doesn’t migrate, and is known to form lasting bonds with its partner.

Extremes of weather in the Seychelles islands are now tearing such pairs apart.

A super El Nino event on the island in 1997, for instance, brought with it record rainfall, and 15.3% of pairs called it quits, a 24-year study found. Pairs also broke up in drought years, their breeding interrupted by the unavailability of food (since most insects lay their eggs in water).

Overall, separation rates varied from 1% to 16% a year, with sharp rises recorded in years of extreme wetness or dryness.

Maintaining body temperature during periods of extreme rainfall could also raise stress levels in the birds and affect their breeding capabilities, found the study, led by Frigg Speelman, a behavioural ecologist at Macquarie University. Such stress could cause females to lay fewer eggs, and this was found to drive males away.

Interestingly, females that lose their breeding position spend so much time and energy looking for a new mate so they can breed again, that they also ended up with lower survival rates.

The study was published in the Journal of Animal Ecology in November.

.

Antarctic snow petrels

This snowy-white bird is so hardy, it evolved to survive at the Geographic South Pole. Now, nesting has become a challenge.

The snow petrel typically nests in crevices in icy cliffs along the Antarctic coast. Year after year, the same pair typically builds their nest together. The female often takes the lead in choosing the site. Both male and female may tend to the home. If ice begins to collect at the entrance to a nest, for instance, the birds have been known to shovel it away with their beaks.

With rising temperatures causing more snowmelt, however, the nests are being overwhelmed, even flooded. The energy spent shovelling or rebuilding is perceived by mates as a poor housing decision by their partner, a recent metastudy found. Some mates simply call it quits, and leave the partner and the troubled home.

The study, titled Climate Change Impacts Pair-Bond Dynamics in a Long-Lived Monogamous Species, based its findings on data gathered across 54 years. It was published in the journal Ecology Letters in December.

.

The black-browed albatross

The black-browed albatross lives for about 60 years and often pairs for life, securing its mate via an elaborate courtship dance in its teen years.

These birds managed their long-distance relationships excellently, migrating separately and spending long months away from each other, but making it back in time for breeding season. Each homecoming was a celebratory affair, with plenty of loud greeting calls, the clashing of bills, and a sort of wings-extended dance.

This has been changing, amid the climate crisis. Research published in the Royal Society journal in 2021 studied 15,500 breeding pairs in the Falkland Islands over 15 years.

In years of unusually warm water temperatures, it found, as populations of plankton, squid, krill and fish shrunk, the average divorce rate rose from 3.7% to 8%.

One theory suggests that albatrosses would have had to fly further or hunt for longer in such years - and this may have contributed to the high separation rates. If one of a pair returned home on time, hoping to breed, and found their mate wasn’t around, they began to seek a new mate rather than wait for one who may not make it home in time, or make it home at all.

.

Sarus cranes

A whole new social dynamic is evolving among the sarus cranes in India.

These crimson-headed birds can grow up to 6 ft tall, have a life expectancy of over 60 years and usually mate for life. Pairs guard their territory fiercely, breed every year and produce 30 to 60 chicks through their lives together.

“They take defending their homes very seriously. Even if they see an intruder flying overhead, they get hostile and emit sharp territorial calls together,” says KS Gopi Sundar, co-chair of the IUCN Stork, Ibis and Spoonbill specialist group and editor-in-chief of Waterbirds: The International Journal of Waterbird Biology.

Since 1998, Sundar has been studying an unexpected evolution in family formats: pairs allowing a third bird, sometimes male and sometimes female, to join the unit.

Before the 1990s, he adds, there were no such trios in the recorded history of the species.

Now, among the 11,591 sarus cranes he studied, he has found 193 trios. (His two papers on the phenomenon were published in 2018, in Waterbirds, and in 2022, in the journal Ecology.)

The key reason a third bird is admitted is to help forage for food. The key reason for the food scarcity is human activity and climate change.

Across states such as Gujarat, Rajasthan and Uttar Pradesh, development, urbanisation and often farming have eaten into the wet marshlands on which these birds nest, breed and forage for shellfish, frogs, snakes, roots, seeds, tubers and other assorted foods.

Trios are typically spotted in drier, degraded habitats, where wetlands have been drained and converted into farms or have dried out for extended periods, Sundar says. In such areas, the scarcity is so severe that even gender roles are forgone. While females typically do more of the foraging in a duo, and males focus on vigilance, all three in a trio share foraging and vigilance duties.

In the evenings one can also hear them calling out together, all three in unison, Sundar says, in the iconic chorus that pairs typically produced.