May 21, 2024

Science – Bocking – Blue tits: more unfaithful offspring among older males – Bavaria

Pöcking (dpa) – Blue tits are nothing but loyal companions; At least one cuckoo baby grows up in several nests. Young men end up having far fewer females than older males – and their more experienced rivals seem to outsmart them when it comes to adventures, according to a research team from Bavaria and Great Britain in the specialist journal PLOS Biology. It is possible that older tits are more successful in fighting, considered more attractive by females or invest more energy into cheating. It is also possible to imagine a combination of factors.

Bart Kempenaers' group at the Max Planck Institute for Biological Intelligence in Sevisen/Bocking examined blue tits (Cyanistes caeruleus) that breed in nest boxes in the forest. In addition to behavioral observations, DNA tests were performed. The analysis first confirmed that male annual blue tits are less successful at producing offspring outside of their partnership. But is it due to inexperience, lack of interest, or immature physical characteristics – or are they rejected by their older counterparts?

The competition has been eliminated

To answer this question, the team moved almost all of the older males in the group in one year, and then compared the reproductive success of the young with data from the previous 15 years. Without competition from their elders, 33 per cent of young people fathered at least one offspring outside their partnership – and in previous years the average figure was just 13 per cent. The blue tit contains approximately 8 to 15 eggs.

Without ancient competition, the cheating of young blue tit males would be as successful as that of older males, is the team's conclusion. The reason behind the low success under normal circumstances is not factors such as lack of interest in extramarital affairs. Indeed, the elderly are the overwhelming competition.

The neighbor wants something from me.

According to the researchers, one thing that could play a role is that they benefit from more foraging experience and therefore have more time and stamina for courtship. They may also be able to identify females willing to cheat more easily and are generally more familiar with specific areas in their territory.

Many songbirds are known to form permanent breeding pairs, but they also mate with others and produce offspring out of wedlock. For blue tits, researchers have already shown that such adventures do not result from chance encounters with strangers, but that cheaters usually know each other for a long time. While the young birds form territories during the breeding season, they like to move together as a flock in the winter.

In the service of development

Researchers hypothesize that the lack of loyalty has evolutionary advantages: males increase the number of offspring without putting more effort into caring for the brood. This gives females an opportunity to increase the genetic diversity of their offspring. This is also important for both parents because blue tits in particular have a low survival rate of only two to three years on average. More than ten years is only possible under ideal conditions.

See also  Why is tuberculosis so hard to beat?

© dpa-infocom, dpa:240416-99-691074/3