Birds, like humans, fall in love too: study

Birds and humans are often remarkably similar when it comes to mate choice and falling in love, a new speed dating experiment suggests.
The study by researchers at the the Max Planck Institute for Ornithology in Germany describes an elegant experiment designed to tease apart the consequences of mate choice.
Researchers took advantage of the fact that the zebra finch shares many characteristics with humans, mating monogamously for life, and sharing the burden of parental care.
Using a population of 160 birds, researchers set up a speed-dating session, leaving groups of 20 females to choose freely between 20 males.
Once the birds had paired off, half of the couples were allowed to go off into a life of 'wedded bliss'.

For the other half, however, the authors intervened like overbearing Victorian parents, splitting up the happy pair, and forcibly pairing them with other broken-hearted individuals.

Bird couples, whether happy or somewhat disgruntled, were then left to breed in aviaries, and the authors assessed couples' behaviour and the number and paternity of dead embryos, dead chicks and surviving offspring.
Strikingly, the final number of surviving chicks was 37 per cent higher for individuals in chosen pairs than those in non-chosen pairs.
The nests of non-chosen pairs had almost three times as many unfertilised eggs as the chosen ones, a greater number of eggs were either buried or lost, and markedly more chicks died after hatching.

Most deaths occurred within the chicks' first 48 hours, a critical period for parental care during which non-chosen fathers were markedly less diligent in their nest-care duties.
Watching the couples' courtship showed some noticeable differences - although non-chosen males paid the same amount of attention to their mates as the chosen ones did, the non-chosen females were far less receptive to their advances, and tended to copulate less often.
An analysis of harmonious behaviour showed that non-chosen couples were generally significantly less 'lovey-dovey' than the chosen ones.
There was also a higher level of infidelity in birds from non-chosen pairs - interestingly the straying of male birds increased as time went by while females roamed less.

Overall the authors conclude that birds vary rather idiosyncratically in their tastes, and choose mates on the basis that they find them stimulating in some way that isn't necessarily obvious to an outside observer.
This stimulation "turns on" the females to increase the likelihood of successful copulation and encourages paternal commitment for the time needed to raise young.
Together these maximise the couple's likelihood of perpetuating their genes through their thriving offspring, researchers said.
The study was published in the journal PLOS Biology.