PLOS ONE Publication
Newsletter 18/09/2015
Migratory birds undertake arduous journeys. But how can a tiny bird achieve to travel of up to 200 hours in a non-stop flapping flight from Europe to tropical Africa, from Canada to Europe, or across the pacific from Alaska to New Zealand? A new collaborative study of Waldrappteam, Austria, with the Institute of Avian Research in Wilhelmshaven, Germany, the University of Vienna, the Vet-Med University of Vienna, the University of Groningen, The Netherlands just published in the journal PONE, takes us a step further in understanding this extreme endurance behavior.
The Waldrappteam trained young Northern Bald Ibises (Geronticus eremita) to follow an ultra-light aircraft. By doing so the researchers were able to experimentally fly various flight ranges during the birds’ guided migration from Austria to Italy. Prior to and immediately after a flight, the scientists around Prof. Franz Bairlein from the Institute of Avian Research sampled blood and combined a stable isotope technique for assessment of energy expenditure with a sport-medicine approach to elucidate the birds’ flying physiological performance, for the first time in free-flying conditions.
Longer flights were energetically cheaper than short flights and cheaper than predicted before. Fuel for these long flights is primarily fat which the birds accumulate prior to migration. Burning fat during the flight provided the necessary energy, but metabolic water as well which makes the birds independent of drinking water. Flight muscles are very well oxygenated by a very efficient respiration. Nevertheless, flying birds do run into anaerobic metabolism and, therefore, accumulate lactic acid. However, they do not appear to suffer from muscle acidosis, likely because they are able to shuttle lactic acid into non-harmful substances by a process from which they gain extra energy as well. This efficient mechanism postpones fatigue and enables migratory birds to make their unique, arduous journeys.
Furthermore, in the context of this human-led migration with Northern Bald Ibises, it turned out that birds are able to save energy by flying in formation (Portugal et al. 2014, NATURE 505, 399-402). This is another mechanism that allows birds to fly such long distances. In the context of the mentioned studies, the Northern Bald Ibis has become a model species for researching the migration of birds.
The Northern Bald Ibis is a highly endangered migratory species. The organization Waldrappteam, together with eight partners from Germany, Austria and Italy, aim to reintroduce the species in Europe. Since 2014, the project is co-financed by the European commission (LIFE+).
Paper Download: http://dx.plos.org/10.1371/journal.pone.0134433
Picture Download: https://www.dropbox.com/sc/1w77vmu3wqon75i/AAC8lHFdJgbXMZMHvpX2A2t9a
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