Zebra Finches make the perfect subjects for such an investigation, because they're monogamous birds that often mate for life, sharing nesting and offspring rearing duties (though they’re also known to enjoy an occasional midnight rendezvous with a sultry neighboring finch). To find out how much love matters when it comes to reproduction, the researchers put single Zebra Finches in a sort of speed-dating chamber, and allowed them to select a partner at will.
Females, who do the mate selecting, clearly had personal preferences, even if their rationale for those choices wasn't immediately clear to the researchers (there’s no obvious beauty standard among these birds). Once the birds were coupled up, though, the scientists butted in and did a little twisted match-making of their own: Half the couples were separated and forced into new pairs, while the other half were left alone. Over the course of several months, all the birds were given time to bond with their partners (forced or chosen) before being released in a communal aviary to breed.
Tension among the arranged pairings was immediately evident. While males in both groups courted their lovers without second thought, female finches in forced pairings were much less responsive to these overtures. The arranged-partnership males, for their part, were more likely to indulge in promiscuity and neglect their parental roles.
The discord between forced partners was even more obvious when the scientists examined how the birds fared at reproduction and chick-rearing. All the female birds laid nearly the same number of eggs, but the survival rate of chicks resulting from self-selected partnerships was 37 percent higher than that of the chicks whose parents had been forced together. The lovey-dovey finches also displayed a more synchronized relationship when it came to the rearing of their young, and they remained physically closer together throughout the study.
