Birds choose mates they are not necessarily attracted to, but are most compatible with. This is what researchers from the Max Planck Institute for Ornithology in Germany found in a new study, according to Discovery News.
The researchers also found that birds, particularly zebra finches, fall in love just like humans, and when they are forced into an "arranged marriage" with a mate not of their choosing, their tendency toward infidelity increases and they give less time to child rearing.
Zebra finches are known to be socially monogamous. Female zebra finches, unlike other female birds, do not choose mates that look strong and healthy - in this case, those that have the most attractive plumage or longest tails - which would indicate a gravitation toward mates with the best genes. They instead seem to choose mates according to their own personal taste, according to Science.
Scientists have long attempted to determine whether zebra finches choose mates based on genetic compatibility or behavioral compatibility. To answer this question, the researchers gathered 160 zebra finches and divided them into four groups, each group containing 20 males and 20 females. The zebra finches were then allowed to pair up on their own.
When they have all chosen their mates, half of the happy couples were left alone while the other half were forced into an "arranged marriage" - their mates were taken away and they were each given a new random mate.
The researchers observed that zebra finches belonging to the happy couples group had a 37 percent greater success in reproduction. However, those belonging to the "arranged marriage" group had three times more unfertilized eggs, with some eggs getting lost or buried, compared to the other group. They also had more chicks that died.
Female zebra finches that ended up with mates they did not choose were less receptive toward copulation, while the males had more tendencies to be unfaithful and copulate with other females. The males also gave less attention to their chicks, resulting in more than 30 percent less chicks surviving and growing old enough to leave the nest.
As for the happy couples group, the researchers could not find an observable pattern for choosing their mates the way they did, leading them to support the hypothesis that zebra finches choose mates based on behavioral compatibility.
Thus, the researchers conclude, love and compatibility play a role in the evolution of zebra finches' lineages.
"To me, love is a peculiar attraction toward a specific individual that is not necessarily shared by other choosing individuals," lead author Malika Ihle said, according to Science. "It seems that the chosen pairs, those 'love marriages,' invested more into reproduction, were more committed, more faithful, and more motivated to raise their family."
The study was published in the Sept. 14 issue of the journal PLOS Biology.
