The paradox of extreme high-altitude migration in bar-headed geese Anser indicus

Proceedings of the Royal Society B
By: , and 

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Abstract

Bar-headed geese are renowned for migratory flights at extremely high altitudes over the world's tallest mountains, the Himalayas, where partial pressure of oxygen is dramatically reduced while flight costs, in terms of rate of oxygen consumption, are greatly increased. Such a mismatch is paradoxical, and it is not clear why geese might fly higher than is absolutely necessary. In addition, direct empirical measurements of high-altitude flight are lacking. We test whether migrating bar-headed geese actually minimize flight altitude and make use of favourable winds to reduce flight costs. By tracking 91 geese, we show that these birds typically travel through the valleys of the Himalayas and not over the summits. We report maximum flight altitudes of 7290 m and 6540 m for southbound and northbound geese, respectively, but with 95 per cent of locations received from less than 5489 m. Geese travelled along a route that was 112 km longer than the great circle (shortest distance) route, with transit ground speeds suggesting that they rarely profited from tailwinds. Bar-headed geese from these eastern populations generally travel only as high as the terrain beneath them dictates and rarely in profitable winds. Nevertheless, their migration represents an enormous challenge in conditions where humans and other mammals are only able to operate at levels well below their sea-level maxima.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title The paradox of extreme high-altitude migration in bar-headed geese Anser indicus
Series title Proceedings of the Royal Society B
DOI 10.1098/rspb.2012.2114
Volume 280
Issue 1750
Year Published 2012
Language English
Publisher Royal Society
Contributing office(s) Western Ecological Research Center
Description 8 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Proceedings of the Royal Society B
Country China;India;Mongolia