For Species That Mate for Life, Love Matters

The male zebra finch's flashy red beak is attractive to his mate. Wang LiQiang/Shutterstock

Flowers and dressing up usually are part of the dating stage of a relationship. Once there's a commitment, those displays of courtship might disappear.

But a new study finds that some birds and other species that often mate for life sometimes continue these affectionate displays long after they decide to stay together. When the males continue to show off their dance moves and bright colors, the females become more invested in taking care of the relationship and their offspring.

"Many bird researchers can tell a story like the experience I once had in the U.K. I caught a female goldfinch, placed her in a bird bag and carried it back to the banding station. All the way back to the station, her mate followed, calling," University Chicago biologist Trevor Price, senior author of the study, said in a statement. "He waited impatiently in a nearby tree as I banded the female, and when I released her, the pair flew off together in close company, twittering. This kind of thing happens in many other species, too, so forming a strong pair bond and emotional attachments between a male and female is evidently not only a feature of humans."

As part of that strong bonding, some males continue to keep their mates interested using fancy shows of affection. Like zebra finches.

Zebra finches are monogamous and often stay with their chosen mates for life, according to the National Audubon Society. Closely bonded, they share housekeeping and parenting tasks, though that doesn't stop them from having occasional flings with other finches.

The male zebra finch has a red beak. If his beak is especially bright, it may elevate his mate's hormone levels. That could result in the female laying an extra egg. That flashy display is good for the male, resulting in more offspring, even though it ends up causing extra work for his mate, who takes care of the babies.

He could increase his chances of procreating by strutting before many females. Instead, he often keeps his mate invested in the relationship by wooing her — and only her — with his good looks. Researchers point out that some fish species do the same thing.

This loyalty can be hard to rationalize, but it's relatively common, say researchers, who explained their findings in the Proceedings of the National Academy of Sciences.

If the males of these loyal pairs didn't show off, then perhaps their mates would lay fewer eggs, which isn't good for either of them.