Divorce is commonly associated with humans, but a surprising new study reveals that birds also experience divorce. Extramarital affairs and extended periods of separation can lead to divorce, not only in humans but also in avian species.
Unlike human divorces, bird separations have distinct characteristics. Approximately 90 percent of bird species are believed to remain monogamous, mating with a single partner during a breeding season. However, some birds choose to divorce their mates and find new partners for subsequent breeding seasons, even when their original mates are still alive.
Researchers from China and Germany conducted a study to unravel the underlying factors behind bird divorces. They identified two significant contributors: male promiscuity and long-distance migrations. The team published their findings in the journal Proceedings of the Royal Society B.
To investigate the divorce patterns in birds, the researchers analyzed divorce rates, mortality data, and migration distances for 232 bird species. They assigned “promiscuity scores” to males and females of each species based on existing information about their mating behavior. They also considered the evolutionary relationships between species to account for the influence of common ancestry.
The analysis revealed a notable pattern: bird species with high divorce rates tended to be closely related, as did species with low divorce rates. This similarity was also observed for male promiscuity. Certain bird species like plovers, swallows, martins, orioles, and blackbirds exhibited both high divorce rates and male promiscuity, while others like petrels, albatrosses, geese, and swans displayed low divorce rates and male promiscuity.
Interestingly, the researchers discovered that higher male promiscuity correlated with higher divorce rates, while female promiscuity did not have the same effect. Male promiscuity, characterized by dividing attention and resources among multiple females, was found to diminish commitment and reduce attractiveness as a partner for the next breeding season. On the other hand, mating with multiple females could enhance a male bird’s fitness. The study suggested that female promiscuity might not have the same consequences because uncertainty about offspring paternity could increase male involvement in parental care.
The study also found a relationship between divorce rates and migration distances. Birds with longer migration distances tended to have higher divorce rates. Asynchronous arrival at breeding destinations could result in early-arriving birds mating with different partners, leading to divorce. Additionally, migrating birds landing in different breeding sites unintentionally caused separation and divorce. Longer migrations also narrowed the breeding window, potentially contributing to divorce as pairs sought immediate breeding opportunities upon arrival.
The researchers concluded that divorce in birds is not solely a strategy to enhance individual fitness or a response to ecological factors like migration but may be influenced by a combination of both. Dr. Samantha Patrick, a marine biology expert from the University of Liverpool, found the study intriguing, particularly the link between migration asynchrony and divorce. She highlighted the potential impact of climate change, which could increase variability in migration timings and potentially raise divorce rates across bird species.
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