Note 78 — PROGRESSION IN OR THROUGH THE AIR. (continued 2)

I have frequently timed the beats of the wings of the Common Heron (Ardea cinerea) in a heronry at Warren Point. In March 1869 I was placed under unusually favourable circumstances for obtaining trustworthy results. I timed one bird high up over a lake in the vicinity of the heronry for fifty seconds, and found that in that period it made fifty down and fifty up strokes; i.e. one down and one up stroke per second. I timed another one in the heronry itself. It was snowing at the time (March 1869), but the birds, notwithstanding the inclemency of the weather and the early time of the year, were actively engaged in hatching, and required to be driven from their nests on the top of the larch trees by knocking against the trunks thereof with large sticks. One unusually anxious mother refused to leave the immediate neighbourhood of the tree containing her tender charge, and circled round and round it right overhead. I timed this bird for ten seconds, and found that she made ten down and ten up strokes; i.e. one down and one up stroke per second precisely as before. I have therefore no hesitation in affirming that the heron, in ordinary flight, makes exactly sixty down and sixty up strokes per minute. The heron, however, like all other birds when pursued or agitated, has the power of greatly augmenting the number of beats made by its wings.