Wild birds will sacrifice access to food in order to stay close to their partner over the winter, according to a study by Oxford University researchers.
Scientists from the Department of Zoology found that mated pairs of great tits chose to prioritise their relationships over sustenance in a novel experiment that prevented couples from foraging in the same location.
This also meant birds ended up spending a significant amount of time with their partners' flock-mates.
And, over time, the pairs may even have learned to cooperate to allow each other to scrounge from off-limits feeding stations.
The results, published in the journal Current Biology, demonstrate the importance of social relationships for wild birds - even when pursuing those relationships appears to be detrimental.
Josh Firth, who led the research, said: '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. For instance, great tits require a partner to be able to reproduce and raise their chicks.
'Therefore, even in wild animals, an individual's behaviour can be governed by aiming to accommodate the needs of those they are socially attached to.'
The research, which was carried out at Oxford University's Wytham Woods site to the west of Oxford, involved the use of automated feeding stations with the ability to decide which individual birds could and could not access the food inside. Birds were allowed access based on radio frequency identification tags that were linked to the feeding stations.
In the experiment, 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.
The researchers found that the birds randomly selected not to be allowed access to the same feeding stations as their partner spent significantly more time at feeders they could not access than birds that were allowed to feed together.
Josh Firth added: '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. This shows how the company an individual bird keeps may depend on their partner's preferences as well as their own.
'Also, when birds were going to feeding stations they couldn't access because their mate was there, they learned over time to "scrounge" from those feeders by taking advantage of the fact the feeders remained unlocked for two seconds after recognising a bird's identification tag. Interestingly, a relatively large amount of this scrounging was enabled by the bird's own partner unlocking the feeding station, suggesting it may be a cooperative strategy.'
The study, titled 'Experimental Evidence that Social Relationships Determine Individual Foraging Behavior', is published in the journal Current Biology, DOI number 10.1016/j.cub.2015.09.075, embargoed until 1700 GMT (1200 EST) on Thursday 12 November 2015. The research was supported by the National Environment Research Council (NERC), the European Research Council (ERC) and the Biotechnology and Biological Sciences Research Council (BBSRC).