Feeding during the winter makes the birds healthier because they don’t have to spend as much energy fighting infections, the first-of-its-kind study shows.
A small change in body temperature can be fatal to humans. Small birds, on the other hand, lower their nighttime body temperature by several degrees during the winter, but just like humans, birds try to conserve energy when it’s cold. If they become infected, the body’s first reaction is to raise the body temperature, which does not go together with the fact that the bird must simultaneously save energy by lowering the temperature.
All have the same temperature
– We expected that birds that had access to bird feeders would have more energy to fight an infection and that they would therefore show a stronger fever response. But our results show the opposite – the birds that did not have access to a reliable food source reacted the strongest to an infection, says Hannah Watson.
When the birds were exposed to a simulated infection, all had almost the same fever temperature. Instead of conserving energy to survive the winter, birds without access to extra food had to use more energy to fight the infection.