Move Over Mating For Life: Among Birds, Divorce Is Actually Quite Common

Bird relationship dynamics are anything but boring! In fact, they can be as complex as those of humans. While some bird couples stick together for life, new research has shown that others swap partners after just a single breeding season. Studying why some birds remain loyal, and others leave can reveal how evolution influences this behavior.
For many bird species, staying with the same partner can result in improved breeding outcomes. They are familiar with each other and can work well together, which greatly impacts their success in raising chicks.
On the other hand, switching partners can come with benefits as well, like finding a stronger, healthier mate or a better nesting spot, which can boost the chances of survival.
Among birds, divorce is actually quite common. It occurs in over 90 percent of socially monogamous species. In some cases, this separation can contribute to more successful breeding and longer lifespans.
Researchers used data from a 24-year study of Seychelles warblers to learn more about the reasons behind bird breakups and how they affect birds’ lives.
Seychelles warblers (Acrocephalus sechellensis) are small songbirds that are socially monogamous. They can live up to 19 years, but their average lifespan is only 5.5 years. They don’t really migrate, so they can be tracked pretty easily.
The new study found that divorce in Seychelles warblers is driven by factors like the age of the male, the length of the relationship, and how many offspring they were previously able to produce. The couples that produced fewer eggs were more likely to divorce by the next breeding season.
Older and younger males had a greater likelihood of divorcing than middle-aged males. The lowest divorce rate was in male birds around the ages of six and seven.
Furthermore, females who go through a breakup have lower rates of survival, indicating that divorce does come with downfalls.

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Generally, divorce in Seychelles warblers is less common than in other species. Overall, only 14 percent of partnerships were found to end in divorce, compared to 69 percent ending because of widowhood. This could be due to competition for the best breeding spots.
The research shows that avian relationships are highly complex and much more intricate than we ever could have imagined. It also suggests that divorce can lead to better opportunities but also comes with risks.
The study found no evidence that divorce caused any short-term fitness benefits. Additionally, the long-term consequences were mostly negative for females.
Scientists hope to gain further insights into how birds adapt their strategies for survival in their natural habitats by examining avian divorce patterns. Moving forward, they will continue to explore all aspects of bird divorce.
The details of the study can be found in Ecology Letters.
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