Love Boosts Fertility in Birds, Study

Birds, like humans, can fall in love.

A new study set out to examine the link between falling in love and reproduction rates in Zebra finches. The research team headed by behavioral ecology Malika Ihle examined a flock of 160 bachelor zebra finches in captivity.

The team paired 20 male and 20 female finches during a long non-breeding season. After the birds started to couple up, the researchers took half of the couples and split them apart. These "broken-up" birds were then paired other "broken up" birds. All of the paired up birds were then given the opportunity to breed. In the end, there were 46 chosen pairs (four pairs had separated) and 38 out of 50 non-chosen pairs.

The research team found that birds who were allowed to choose their own mates ended up reproducing 37 percent more offspring in comparison to the reproduction rates in birds who were paired up by the researchers. Reproduction was measured by factors such as dead embryos, dead chicks and live offspring.

The rate of embryo mortality for birds who chose their own mates and birds in "arranged marriages" was the same. Birds who chose their own mates, however, had a better chick mortality rate. The researchers concluded that when finding a mate, behavioral compatibility, which was recorded via visual observation and voice recordings, can play a factor.

"The percentage of eggs that contained a dead embryo was equal between chosen and assigned pairs. In contrast, the percentage of nestlings that died before reaching independence was twice as high if chicks were raised by assigned pairs", said Dr. Ihle. "If a chick hatched in such a nest, it only had a 50% chance of surviving."

In cross-fostering experiments, the team also found that embryo mortality was affected by the genetic compatibility of the bird parents. Chick mortality, on the other hand, depended on the behavioral compatibility of the foster bird parents.

The study was published in PLoS Biology.