When it comes to cheating, older birds have a mating advantage

Forget puppy love — in the world of blue tits, it’s the older, experienced males who win the game of extra-marital affairs. A new study sheds light on why young male blue tits struggle with mating outside of their primary partnerships.

Extra-pair paternity and blue tits mating

Many bird species engage in what scientists call “extra-pair paternity.” It refers to a situation where a female bird mates with a male other than her primary social partner. The offspring resulting from this extra mating will have a different biological father than the male who is helping to raise them.

Younger male birds often struggle to achieve extra-pair paternity. It’s uncertain if their limited success stems from an inability to attract mates due to inexperience and lack of skill. Alternatively, their challenges could be related to competing against older, more seasoned males.

Blue tits mating pattern

To find out, researchers at the Max Planck Institute for Biological Intelligence in Germany spent 15 years observing a wild population of blue tits.

Researchers carefully studied blue tits over many years to understand the mating patterns. In a controlled intervention, they removed the majority of older males from the population.

This allowed scientists to directly observe if young males had more success fathering extra-pair offspring in the absence of competition from their elders.

The removal of older males led to a significant increase in the reproductive success of younger males. This indicates that competition with older, more experienced birds is one of the primary reasons young males struggle with extra-pair paternity.

Older blue tits mating success

So, what gives the older birds their edge? Scientists have a few theories:

Theory 1

Older males could be stronger and better at fighting than their younger counterparts. This physical advantage helps them chase away rivals and secure access to females interested in mating outside their main partnerships.

Years of experience might have made them savvier fighters, able to use better strategies in territorial disputes.

Theory 2

Adult males may dedicate more time and energy specifically to seeking additional mating opportunities than younger males. They might have developed better strategies over time to find and successfully court potential extra-pair mates, leading to a higher chance of reproductive success.

Theory 3

Females could find older males more attractive because their age implies they have survived longer and possess good survival skills. These ‘good genes’ would be desirable to pass on to offspring.

Perhaps older males are better at courtship displays like singing or have other characteristics that females find attractive

Importantly, it’s likely that these theories don’t work in isolation. A combination of superior fighting abilities, greater effort, and attractiveness could all contribute to the older male’s advantage.

The authors add, “Our study indicates that the generally observed low extra-pair siring success of first-year males is due to competition with older males. This age effect is thus mediated by the social environment, at least in the blue tit.”

More about extra-pair paternity

As discussed, extra-pair paternity is a fascinating phenomenon in the avian world, where birds, despite forming social bonds or pairings, engage in mating outside these primary relationships.

This behavior is not unique to blue tits mating patterns; it is widespread across many bird species, each with its own strategies and implications for reproductive success.

In the bird kingdom, extra-pair paternity can influence genetic diversity and the evolutionary fitness of populations. Birds like warblers, swallows, and even the iconic sparrows have been observed engaging in extra-pair paternity.

Factors influencing extra-pair paternity

Several factors can drive the prevalence and success of EPP among birds:

• Genetic benefits: Females might mate with multiple males to enhance the genetic quality of their offspring. This can include seeking males with superior physical traits or those who might contribute new genetic material to the population.
• Resource acquisition: In some cases, females engage in EPP to gain access to better territories or more resources provided by multiple males.
• Mate quality: EPP can also be a strategy for compensating for a socially paired male that might be suboptimal due to age, health, or genetic compatibility.
• Social structure: The social organization of a species can greatly influence EPP. Species with high densities or communal nesting areas may see higher rates of EPP due to increased opportunities for mating.

Broader implications

This research on blue tits not only sheds light on their mating strategies but also casts a broader question on avian behavior: Does the adage “older and wiser” universally apply when it comes to mating success across different bird species?

While this study highlights age as a significant factor in mating prowess among blue tits, it opens the door to examining whether older birds generally have a mating advantage in other species as well.

Furthermore, the study prompts us to consider other potential influences that could affect a bird’s success in mating beyond just age. Factors like physical health, environmental conditions, and even the density of the population could play crucial roles.

Understanding these dynamics more comprehensively will likely fuel further research, aiming to uncover the intricate layers of mating behavior in the avian world.

This could lead to a deeper understanding of evolutionary strategies and social structures among birds, providing insights that could extend even beyond ornithology.

The study is published in the journal PLOS Biology.

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