Humans are not the only species with rising divorce rates. New research shows that birds are separating from their partners, and the reasons are familiar: cheating and long-distance relationships.
The vast majority of bird species breed in monogamous pairings. For many, this can last a lifetime. However, some birds change their partner after one breeding season. This “divorce” can happen for many reasons.
Stress, climate change, or too shy?
In 2021, a study found that climate change is a cause of albatross separation. As water temperatures have increased, their divorce rate has risen from 1% to 8%. Warmer seas mean less food, and some birds prioritize hunting over breeding, arriving late to the breeding sites. For others, lack of food leads to stress, and viable offspring are not possible. Another study from 2022 showed that female albatrosses were more likely to give up on a partnership with a shy male.
Most studies focus on one species of bird, but the new research has found two universal reasons birds part ways. The first is male promiscuity and the second is long-distance migrations.
A pair of black-browed albatrosses. Photo: Shutterstock
Promiscuity scores
The German-Chinese research team pored through published data and journal articles documenting separation in bird pairings. In the end, they collected information on 232 bird species. The data examined migration distances, mortality data, and behavior. Based on behavior, they were able to give the males and females of each species a promiscuity score.
Interestingly, male promiscuity showed a clear link to separation, but female promiscuity did not.
“Plovers, swallows, martins, orioles, and blackbirds had high divorce rates and high male promiscuity, whereas petrels, albatrosses, geese, and swans had low divorce rates and low male promiscuity,” the research team wrote.
In contrast, females showing attention to other males had little effect. Instead, female promiscuity may lead to better male parenting.
“Each male, uncertain about his paternity, may invest more effort in caring for the offspring to ensure their survival,” said co-author Zitan Song.
The second clear reason for divorce was long migrations. The further each bird had to travel to reach a breeding site, the more likely they were to arrive at different times, fly to the wrong site, or die on the way. All these factors could lead to separation.
