Feathered friends favor fruity flavonoids

Fruit-eating birds actively select fruit with the highest concentrations of antioxidants – compounds that help them maintain a healthy immune system – ecologists have found. This is the first time that a group of antioxidants known as flavonoids have been found to boost the immune system in studies on living animals, as opposed to test-tube studies. The results are published online in the British Ecological Society’s Functional Ecology.

Researchers from the University of Freiburg and the Max Plank Institute for Ornithology in Germany offered a group of blackcaps a choice of two foods. The foods were identical in all respects except for the amount of flavonoids they contained, and the researchers found that the blackcaps actively selected the food with added flavonoids.

As well as the food selection experiment, the study also looked at whether or not the flavonoids had an impact on the birds’ health. They found that, compared with birds not fed the antioxidants, blackcaps that ate modest amounts of flavonoids for four weeks had stronger immune systems.

According to the lead author of the study, Carlo Catoni of the University of Freiburg: “We fed the birds an amount of flavonoids that they would obtain by eating 1-2 blackberries, bilberries or elderberries a day. We used this modest intake of flavonoids because high quantities are only available during the limited time of maximum berry abundance. Our study shows for the first time that flavonoids are beneficial compounds that can boost the immune system in a living organism. We also found that wild birds actively select food containing flavonoids. Our results have important implications for the study of ecology and immunity in birds, and for the evolution of the relationship between plants and the birds and animals they rely on to disperse their seeds.”