Love affairs or long separations are usually synonymous with divorce in the case of human couples, but similar factors seem to play a role in the case of separations between birds, reports The Guardian, citing News.ro.

It is estimated that more than 90% of bird species usually have one mate for at least one breeding season, if not longer. However, some monogamous birds change partners for the next mating season, even if the original partner is still alive, a behavior called “divorce”.

While a number of studies have looked at possible factors associated with such splits, experts say they tend to focus on single species or groups of species.

Now researchers say they have identified two key factors linked to divorce in many bird species: promiscuous male sex lives and long-distance migrations.

Study of promiscuity in birds

Researchers from China and Germany describe in the journal Proceedings of the Royal Society B how they built on previously published data on divorce rates for 232 bird species with data on mortality and migration distances.

The team also assigned males and females of each species a separate “promiscuity score” based on published information on the birds’ behavior.

They also conducted an analysis based on evolutionary relationships between species to account for the effects of common ancestry.

The results show that species with particularly high divorce rates tended to be closely related, as were species with particularly low divorce rates. A similar picture was observed for male depravity.

“For example, ladybirds, swallows, sparrow hawks, barn owls and blackbirds had high rates of male divorce and promiscuity, while albatrosses, geese and swans had low rates of male divorce and promiscuity,” the team wrote.

Although scientists have found that greater men’s promiscuity is associated with higher divorce rates, the same cannot be said for women’s promiscuity.

“When a male has a promiscuous sex life, it is often perceived as a reduction in this commitment, as his attention and resources are divided between several females. This can make him less attractive as a mate and thus more likely to be “divorced” in the next breeding season. Instead, a male can increase his fitness by mating with more females,” said study co-author Dr. Zitan Song from the Max Planck Institute for Animal Behavior in Germany.

Thus, divorce rates may increase where men have more opportunities to have promiscuous sex lives.

What types of birds are most susceptible to “divorce”

The team also found that species with longer migration distances have higher divorce rates.

“After migration, pairs may arrive at their destination asynchronously, leading to a situation where the earlier arrival may mate with another partner, resulting in ‘uncoupling’. In addition, migration may cause pairs to land at different breeding sites, causing “divorcement” due to accidental loss. This effect increases as migration distance increases,” Song said.

The team observed that longer migrations reduced the mating window.

“Divorce may promote immediate reproduction upon arrival rather than waiting for a previous mate,” Song said.

The researchers also found that mortality rates and migration distance were apparently related to male promiscuity, suggesting a potential indirect effect on divorce.

The team says the results suggest that separation in birds may not simply be a strategy to increase individual fitness or a response to environmental factors such as migration, but may also affect both at the same time.