A new study has found that birds are like humans in terms of choosing their mate and exhibiting love and courting behaviors toward those that they do and don't like.
With this, birds are not fans of arranged marriages as they tend to become less successful in breeding and taking care of their offspring when they end up with birds they do not love.
Previous studies about the choice of mates targeted the general preferences of quality factors, speculating that all species have the same notions of what is attractive. However, some species have exhibited characteristics that suggest that mating choice appears individualized, meaning some specific genetic and behavioral compatibility may be valuable.
In this new study by experts from the Max Planck Institute for Ornithology, the researchers looked into the outcomes of mate relationships between zebra finch (Taeniopygia guttata) birds, under controlled and uncontrolled situations.
The researchers examined a total of 160 birds, each of which was given the opportunity to choose their partner from a flock of 20 birds of the opposite sex during a long, nonbreeding period. This setup emulates natural occurrences in which birds do not reproduce when the surroundings are not conducive but still engage in relationships or bonds regardless of the season.
After this part of the test, the researchers focused on the female birds. The experts assigned the female birds from the first pairings to two groups. In the first group, the females were allowed to choose their own mates while the second half were forced to pair with a male bird chosen by another female.
All the pairs were then caged for a period of months to impose bonding among pairs in the forced-paired group. After this, the bird pairs were placed in separate cages, giving them the chance to breed for approximately five months in communal aviaries. Each group had three pairs of birds from different treatments: the birds given free choice during nonbreeding periods; forced-paired birds in cages; and mating in communal aviaries.
In the second breeding season, the researchers separated two-thirds of the pairs from the first breeding season. The birds chose a new mate and were subjected to the same or different treatment. One-third of the pairs retained their chosen or non-chosen mates from the first breeding season.
In total, the researchers were able to study 46 bird pairs that were allowed to be with their chosen mate and 38 bird pairs subjected to forced-pairing.
The findings of the study, published in the journal PLOS Biology, showed that the chicks that came from birds that mated with their chosen partner exhibited a 37 percent higher survival rate compared to the chicks of the forced-paired birds.
In the "arranged marriages," more eggs were either unfertilized or buried and subsequently not found, and more offsprings succumbed to death after hatching. The male birds also showed less diligent protective actions toward the eggs during the hatching period.
Death of embryos was actually the same in both groups. With this, the researchers suggested that the lower survival rate of eggs by forced pairs may be due to poor parenting rather than genetic factors.
In the end, the authors conclude that chosen pairs showed more optimal fitness characteristics compared to the forced-paired group because of behavioral incompatibility rather than genetics.