Many bird couples exemplify "till death do us part" by mating for life, and now a new study finds that these pairs will even sacrifice access to food in order to stay close to their loved ones over the winter months.
The determination shows just how valuable stable relationships can be, at least in the bird world.
"The choice to stay close to their partner over accessing food demonstrates how an individual bird's decisions in the short term, which might appear sub-optimal, can actually be shaped around gaining the long-term benefits of maintaining their key relationships," project leader Josh Firth of Oxford University said in a press release.
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The study is published in the journal Current Biology.
Firth and his team focused on birds called great tits, but it's suspected that the findings could apply to many species. Geese, swans, cranes and eagles, for example, are primarily monogamous. Lovebirds, which are actually a small species of parrot, mate for life as well, and spend many of their days affectionately doting on their mate.
In terms of great tit couples, an experiment demonstrated their loyalty.
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The researchers placed automated bird feeding stations at Oxford University's Wytham Woods site. The stations were set up such that the mechanisms could "decide" which individual birds could and could not access food, based on what particular radio frequency identification tag - worn by the birds - was detected.
The scientists rigged the feeders so that mated pairs of birds were unable to access the same feeding stations as each other, meaning the male could only access the feeding stations that the female could not, and vice versa.
They found that, more often than not, the birds elected to be with their mates rather than get the easy meal. As for humans, hanging around a loved one often involves dealing with their friends and relatives, too.
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"Because these birds choose to stay with their partners, they also end up associating with their partners' flock-mates, even if they wouldn't usually associate with these individuals," Firth said. "This shows how the company an individual bird keeps may depend on their partner's preferences as well as their own."
Another finding from the study is that the clever bird pairs figured out that the feeders remained unlocked for two seconds after recognizing an identification tag. Rather than go to a location where one, but not the other, could more easily obtain food, the two stayed together and worked out a system.
As one used its tag to unlock the feeding station, the other would hurry in to scrounge whatever food it could in the two seconds. The researchers refer to this as a "cooperative strategy," suggesting that the birds probably join mental forces to solve countless other problems.