Like most birds, the great tit is (mostly) monogamous. Every winter pairs of the stunning yellow-breasted songbirds (above) reunite for the upcoming breeding season and spend the bulk of their time together—staking out territory, building nests and even foraging. The strength of their bond is palpable, but what would happen if the birds were forced to choose between love and food?

To find out, University of Oxford zoologist Josh A. Firth and his colleagues arranged a set of feeders in a forest near the English countryside. Some of those feeders were set to open only for birds that had been tagged with odd-numbered microchips; others allowed access only to those tagged with even numbers. Thus, pairs with matching assignments could open the same feeders and feast on sunflower seeds together. Mismatched couples, on the other hand, were forced to dine at different venues.

Over the course of three months the researchers monitored 17 couples, including seven odd-plus-even pairs that could not eat at the same feeders. They found that birds from those mismatched pairs visited inaccessible feeders nearly four times as often as those from matched pairs, suggesting that mates were sticking together even if it meant one of them lost out on a meal. The results were published in December in Current Biology.

Great tit couples may remain side by side even when one of them is hungry because they will need each other later on. “The pair bond is vital for great tits,” Firth says. “Single parents cannot cope with the demands of raising a brood alone. Their only hope for success depends on having a supportive and reliable partner.”

Andrew King, a behavioral ecologist at Swansea University in Wales, says that these findings mirror observations in a wide variety of animals, ranging from primates to fish. “Getting less food and foraging with a ‘friend’ may still be better than getting more food and foraging [alone],” he says. In fact, many of the thwarted birds in the experiment eventually learned to scrounge quickly from their partner's food, taking advantage of a two-second window before the feeders locked back up.