16 January 2015
Vol 347, Issue 6219

About The Cover

Cover image expansion

COVER Bar-headed geese (Anser indicus) flying above the Tibetan Plateau. Rather than migrate high above the ground at a steady altitude, these birds fly only as high as the undulating terrain requires. This flight path keeps them in relatively dense air and reduces energy expenditure. Measures of heart rate and wingbeat frequency confirm that the birds usually fly comfortably within their physiological capabilities. See page 250.
Photo: Coke Smith