Putting out food for small birds in your garden during the wintertime helps them fight off infections. This is the conclusion of a study by researchers from Sweden, who discovered that such offerings give birds more energy, which allows them to maintain a higher body temperature during winter nights. This, in turn, means that — when they get sick — they have to expend less energy to raise their body temperature to help fight off pathogens.
While even small changes in body temperature can prove fatal for us humans, small birds slow their metabolism and lower their body temperature by several degrees during winter nights.
This allows them to conserve energy by lowering the temperature that they need to maintain in the face of colder conditions.
A problem occurs, however, when the birds get ill. Their bodies’ instinctive reaction is to raise their temperature in order to fight the infection.
This, however, clashes with the imperative to save energy at night by doing the exact opposite.
The new study was undertaken by biologist Dr Hannah Watson of Lund University and her colleagues.
Dr Watson said: “We investigated how access to food during winter affected the balancing act between maintaining a low body temperature and in order to save energy and the possibility of raising body temperature in order to fight infection.”
The researchers found that birds who were fed during the winter did not need to lower their body temperature as much at night as those who did not have access to feeding tables.
The team believe that the luckier, fed birds were able to gather enough energy from food during the day to survive a winter night in spite of maintaining a higher body temperature.
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The team also found that when exposed to a simulated infection, both fed and unfed birds had essentially the same body temperature during the resulting fever.
As a result, instead of being able to conserve energy to help survive the winter, those birds without access to extra food were forced to use more energy to raise their body temperature high enough to help combat infection.
Dr Watson added: “We had expected to find that the birds that had access to bird feeders would have more energy to fight an infection, and that as a result they would exhibit a stronger fever response.
“Our results, however, show the opposite — birds that did not have access to a reliable source of food had the strongest reaction to infection.
“This enabled them to reach the same fever temperature as the birds with extra food.”
The use of feeding tables has a complicated relationship with avian infection — with those that visit them at risk of exposure to more infection via the spread of pathogens.
At the same time, however, the finding of the study indicates that the food they receive from humans can help make their immune defences more tolerant to infection.
Dr Watson concluded: “A lot of people like to feed the birds. Our study shows that this can have a positive effect on the capacity of our small birds to fight an infection.”
The full findings of the study were published in the Journal of Animal Ecology.