The rook displayed great power of wing, twisting and turning, now descending or turning on one side to glide more rapidly, and uttering short 'caws' of eagerness or anger; but, just eluding the heavy rush of its pursuer, the swift doubled and darted away before it, as if tempting the enemy to charge, and then enjoying his disappointment.

Several other swifts wheeled above at a distance, apparently watching.

These evolutions lasted some minutes, rook and swift rising higher and higher into the air until, tired of being chased, the swift went straight away at full speed, easily outstripping the rook, which soon desisted from the attempt to follow.
When birds are thus combating, the chief aim of each is to get above the other, as any elevation gives an advantage.

This may be continually noticed in spring, when fighting is always going on, and is as characteristic of the small birds as the larger.

At first I thought it was a crow after the swift, but came to the conclusion that it must be a rook because the battle began over the rookery and afterwards the aggressor sailed away to where some rooks were feeding.
Nor would a crow have exhibited such agility of wing.