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ABSTRACT The basis used for estimating lift and drag coefficients is explained. A method of obtaining a photograph of a bird flying at known airspeed and rate of sink is described. 96 % of the speed measurements fall between 22 and 65 ft./sec., the average being 40 ft./sec. A maximum lift coefficient of 1-8 can be achieved. Wing area is reduced with increasing speed. The feet are used as airbrakes. A comparison of the minimum drag coefficient (0·06) with the maximum estimated power output of the pectoral muscles leaves only a narrow margin of power available for climbing. The performance diagram gives a minimum gliding angle of 1 in 812, and a minimum sinking speed of just under 4 ft./sec. The fulmar has apparently sacrificed the ability to soar dynamically over the sea in order to be able to fly slowly and thus utilize light upcurrents at cliff faces.
C. J. Pennycuick (Wed,) studied this question.