Oxidative Stress in Endurance Flight: An Unconsidered Factor in Bird Migration

Migrating birds perform extraordinary endurance flights, up to 200 h non-stop, at a very high metabolic rate and while fasting. Such an intense and prolonged physical activity is normally associated with an increased production of reactive oxygen and nitrogen species (RONS) and thus increased risk of oxidative stress. However, up to now it was unknown whether endurance flight evokes oxidative stress. We measured a marker of oxidative damage (protein carbonyls, PCs) and a marker of enzymatic antioxidant capacity (glutathione peroxidase, GPx) in the European robin (Erithacus rubecula), a nocturnal migrant, on its way to the non-breeding grounds. Both markers were significantly higher in European robins caught out of their nocturnal flight than in conspecifics caught during the day while resting. Independently of time of day, both markers showed higher concentrations in individuals with reduced flight muscles. Adults had higher GPx concentrations than first-year birds on their first migration. These results show for the first time that free-flying migrants experience oxidative stress during endurance flight and up-regulate one component of antioxidant capacity. We discuss that avoiding oxidative stress may be an overlooked factor shaping bird migration strategies, e.g. by disfavouring long non-stop flights and an extensive catabolism of the flight muscles.

Citation: Jenni-Eiermann S, Jenni L, Smith S, Costantini D (2014) Oxidative Stress in Endurance Flight: An Unconsidered Factor in Bird Migration. PLoS ONE 9(5):
e97650.

https://doi.org/10.1371/journal.pone.0097650

Editor: Kevin McGraw, Arizona State University, United States of America

Received: February 18, 2014; Accepted: April 22, 2014; Published: May 15, 2014

Copyright: © 2014 Jenni-Eiermann et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: The study was financed by the Swiss Ornithological Institute which is a private foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

This study investigates oxidative stress in free-flying migratory birds during endurance flight.