Ravens in aerobatic flight

Play the video below to watch ravens in aerobatic flight over a hill near Kanab, Utah, USA. The clip has three parts:

• A pair of ravens flying together, with one raven repeatedly flipping onto its back while in flight.
• A single raven repeatedly passing an object between its bill and claws. (Another instance a raven participated in inverted flight with another raven while carrying a stick of wood in its claws, and also passed it bill to claws.)
• An distant view of the hill showing the general pattern of flights.

The ravens didn't appear to be feeding. Wikipedia says that crows do a sort of aerial jousting to establish a pecking order. Others have suggested it is courtship or pair-bonding behaviour, or simply playing (it certainly looks like fun!).

This was mid-May in 2008, at around 6pm, and there was a breeze from the west (left) providing lift up the hillside.