As soon as the male (right) alit on the perch, it began to utter curious sounds. It then spread its wings, and the female responded with a wing spread of its own,
as well as similar sounding noises. This amorous dance lasted about five seconds. I guess that the female's behavior signalled that it was "available and amenable" to the male's overtures.

The male, encouraged by the willing demeanor of the female, makes a flying leap behind the latter.

The male makes a perfect landing. The expression on the birds' faces are almost human-like.
The male's eyes are a picture of sheer determination and dominance, while the female pulls her head back and closes her eyes, seemingly in ecstasy.

Four frames (KZ2L1554 to KZ2L1557) are similar, and this is the one presented. The male appears to be in the "decisive moment,"
and it flaps its wings to try to maintain balance. The same determined look is on his face, while the female is motionless in bliss, with her head pulled back.
As an incentive to procreation, Mother Nature must have designed this bird act to be equally as pleasurable as that in humans.

With the ascent to Mt. Everest over, the male prepares to disengage. The female, for the first time since she was mounted, opens her eyes.

Before disengagement, both birds appear to stare heavenward, seemingly thanking whatever avian gods are there for the success of the act.
The male spreads his wings, as if he wishes to gather momentum before letting go of the female.

The male's wings are coiled for take-off, not unlike an Olympic gymnast about to leave the parallel bars.

The male's wings trace a beautiful C-shape as he flies off the female..... And that, folks, is how cute, little baby wood-swallows are made.
These aren't delivered upon order (like a pizza) by the friendly neighborhood stork. Rather, these are the product of active engagement by Mom and Pop wood-swallow....;-)