Diver and Glider took off from the cliff and nose-dived together, side by side, before pulling out of the dive with little apparent effort; they separated briefly and began their climb using the updraft from the air that collided with the cliff as it traveled, each bird rotating in opposite direction, thus creating, together, a helix in the air.

At their maximum altitude, the two did a half-looping and roll to find themselves side by side again; they separated doing a roll, one up, the other down to find themselves back at the same altitude.

The couple decided to do some lateral gliding to rest a bit, while gaining speed from the drop. Then both entered barrel rolls, one bird ending on his back above the other one, wings expanded to the maximum to gain altitude as a couple. Finally, the two birds of prey decided to conclude by an exchange of vows: each caught a fish, and exchanged their catch in midair. The trick consisted for each bird from heading towards each other, drop their catch and manoeuvre in such a way as to catch the other’s fish without colliding in midair.

The exchange made successfully, the two birds took their meals to an overhang, away from others, and proceeded to feed each other tidbits of the fish. That concluded the preliminaries before they began building a very elaborate nest.

During the next month, they kept building their nest, and mounted each other repeatedly.

*  *  *

“This, ladies and gentlemen, concludes the presentation of the mating ritual of the mountain cliff eagles. Unfortunately, we were unable to access the cliff top, due to the nature of the rocks. We hoped to record the hatchlings’ first flight, but our research came to an end before this could be done.”

Solid applause followed the video representation of the mating flight of the mountain cliff eagles.

“At this point, I would like to take questions.”

One young man walked to the microphone and looked at the professor.

“Sir, my name is William Robertson. I am a graduate student in Ornithology. Could we see a stopped-frame of the presentation presenting the two birds side by side as they were at the low climb off the updraft? I would like to look at their fully expanded wings coloring.”

“Sure, young man. If I remember right this was around the fourth minute of the presentation. Please wait while we position the correct frame.”

A few minutes later, the two birds were visible in their full glory, all colors marking clearly apparent, both from the front and the top.

“So, aren’t they beautiful?”

“Oh yes they are, but there is something strange here.”

“What is it? I don’t see anything out of the ordinary, apart that we have a beautiful example of a mating dance in mid-air.”

“Well, you see, in eagles, like in every avian species recorded, the male has the beautiful colours to attract a drab, rather smaller female. Dimorphism is a fundamental characteristic of quite a few species of birds, including eagles. Look at these two.”

“So, I still don’t get it.”

“They are both very colourful, very large, and, in my book, very MALE, professor. What you recorded was the mating flight of a couple of GAY eagles!”

The room sat motionless, stunned silent by what was the most obvious of all, yet that none of the eminent scientist assisting the symposium had noticed.