Migratory birds must take rest periods during their migration journeys to boost their immune system, according to a study published in the scientific journal Biology Letters.
We all know that too much exercise and not enough sleep is bad for your health. Now, it seems that migratory birds know this too. They often enjoy rest periods during their migration to recover and boost their immune system.
After a period of intense physical activity, animals need a period of recovery. This includes lowering heart rate and repairing injured muscles, but less visible systems also need to recover. For example, physical activity can lower an individual’s immune defences.
When birds migrate, they sometimes stop in one place for a few days to eat and rest. It was believed until now that this was simply to eat and build up fat reserves to allow them to fuel the rest of the journey. However, now researchers from Lund University, Sweden, have shown that birds also build up their immune system. This happens fast; a few days is enough.
“This is the first time that this has been demonstrated in wild migratory birds. Our study shows that migratory birds’ stops serve other purposes besides just ‘refuelling.’ They also need other physiological systems to recover. You could compare it to pulling off the motorway into a service station. That is not just for the purpose of refuelling; you might also need to recover,” said Arne Hegemann, a biologist at Lund University who conducted the study with colleagues from the Institute for Avian Research in Germany.
For this study, the team examined small migratory birds – such as chaffinches, dunnocks, and common redstarts – and evaluated changes in their immune system during rest periods in their journeys. “If you see a little bird in your garden or in the park during the autumn and you know that it is heading to southern Europe or Africa, it is fascinating to think about why it is taking a break. If they do not get food or rest, their immune systems cannot recover – which is when they risk becoming ill,” said Hegemann.
By gathering results from different birds and different species, the authors show that migratory birds can restore immune function during rest periods between flights. “It is fascinating just how much we are still to learn about avian migration and exciting new things emerge regularly. This provides an important part of the puzzle of how migratory birds cope with the physiological challenges they are faced with on their long journeys,” concluded Hegemann.
Eikenaar C, Ostolani A, Hessler S, Ye EY, Hegemann A. Recovery of constitutive immune function after migratory endurance flight in free-living birds. Biol Lett. 2023 Feb;19(2):20220518. doi: 10.1098/rsbl.2022.0518.