He althy Second Choice
The most colorful types get the best brides: At least that was the standard in bird research for a long time. But everything has its price, because too many beauties could promote inbreeding in the long run - the chance for scorned fathers-to-be.
What doesn't the bird male do to not only land physically with the beloved: sing at the top of his lungs, tease rivals and, above all, advertise with an attractive appearance. This is the only reason why peacocks adorn themselves with otherwise rather cumbersome long tail feathers, frigate birds inflate voluminous red throat pouches and dancing birds risk their lives in the green tangle of leaves of the jungle with screaming bright colors of feathers, which irritate every observer in their own way.
But if all the female birds only wanted to get involved with the beauties of their clan, a huge part of the species' gene pool would be wasted. The result: In the long run, inbreeding would occur and thus impair genetic he alth. This in turn would make the populations more susceptible to disease or environmental influences and thus endanger the survival of the species. The women's first choice is therefore not always the best choice, especially if the chosen one is too closely related to them.
On the one hand, the selection criteria based on appearance drive evolution in the long term in the direction of increased attractiveness, which could, however, standardize the genome in the long term. On the other hand, the females actually prefer males that are as genetically distant as possible, which in turn should theoretically lead to a wider range of equally simpler plumage – and thus the exact opposite.
This dilemma has long presented the ornithologists with a greater mystery, which Kevin Oh and Alexander Badyaev from the University of Arizona in Tuscon may now have clarified, at least for the American house finch (Carpodacus mexicanus). For ten years they observed a population of these birds in Missoula, Montana. They tagged and photographed the animals to identify them, took blood samples for DNA testing, and tracked their hormone levels throughout the year.
Little by little, they gained insight into the intimate details of the lives of 12,000 bullfinches. Of course, special attention was paid to the mating and breeding success of the various males and how their offspring then struggled through life. These explorations were facilitated by the fact that females can only be fertilized within an individual ten-day window during mating.
Oh and Badyaev were therefore able to find out from all expectant mothers whether they might have gotten involved with a relatively closely related pretty boy or a less attractive but genetically very different family founder - even infidelities did not go unnoticed.
The observations of the two researchers now offer the gray mice both sorrow and consolation, at least in the feathered world: In the exuberance of the feelings of the spring hormone surges, the females present chose, as far as possible, those partners with the most pronounced red parts on their faces and on the chest - whether it was possibly a distant uncle or cousin. On the other hand, more simply dressed conspecifics, which could only shine with rather muted yellowish-brown hues, went largely empty-handed. And that's even if their genetic make-up had been advantageous in comparison.
But this is by no means a reason for the finch men to despair, because in the course of the season they finally got a second chance. After all, when all the color bucks were taken and had to take care of the domestic duties of looking after mother and child, females from other regions who had not yet been taken in usually flew to the bachelors' territories. And since the urge to pass on one's genes was greater than her patience to wait for more conspicuous males, a new round of mating took place.
Naturally, partners with very different genetic material mixed with each other, so that the genome of less attractive specimens of the species was also preserved. In this way, in the long run, evolution rewards both those males who can invest in magnificent plumage and those who keep the gene pool varied. According to the scientists' findings, however, this system only works because the male finches remain stationary while young females migrate
For these first-time mothers, however, it was no harm not having gotten the prettiest guys: Because of the large genetic differences, their offspring had the highest survival rates in comparison. So at least sometimes it's what's inside that counts, even with house finches.