I have been so fortunate as to obtain the views of several well-known authorities on this difficult question—the comparative maximum speed of the swift and the peregrine.
Colonel Meinertzhagen says:
“I should certainly say that the swift is the fastest British bird, both in its normal speed and accelerated. But any of the falcons could catch it, if caught unawares, by stooping, or perhaps two hunting together. If the swift had, say, ten seconds’ warning,[14] I do not believe any falcon could touch it. As regards endurance, those birds with the greatest endurance are the swifts, swallows, petrels, and gulls. Swifts are probably endowed with the greatest powers, being denied by nature the advantages of perching, alighting on water, or resting on the ground. I have recently been studying the power of flight of various groups of birds, and find that the wings of the swift and petrel groups have wing outlines best suited for both endurance and speed. The falcon has a wing intended for short rapid flights and not for endurance.
“You have doubtless seen falcons hunting. When they set out on a regular hunt they are not usually much faster than their quarry, unless it is some unfortunate non-game bird, and they only gradually overtake it. But I think a falcon usually makes full use of surprise and force of gravity. If these fail, he often abandons the chase, recognising that wearing a bird like a golden plover or teal down by sheer endurance and honest straightforward flying is a troublesome and not always successful task.”
Major C. R. E. Radclyffe writes:
“The point you raise re the relative speed of swifts and other birds is a difficult one to decide.
“I have, however, a strong recollection of a brother falconer (I cannot remember who it was) telling me that his trained merlins could easily overhaul a swift, and he told me that once or twice they had killed them. But this was many years ago, and I am not able to remember all the facts.
“I have often stood on the bridges here and watched swifts passing in hundreds close past me. They appear to be moving very fast when hawking after flies near the surface of a river.
“There is a long stretch of broad water in the river in front of my house here, and often there are hundreds of swifts flying up and down it. They go about half a mile dead straight and then turn back over this stretch of the river.