Sixteen minutes later, the stalemate still goes on. They hardly move except that if you were watching it live, you could see their chests moving as they breathe!
Finally, after 20 minutes locked together, one bluetit breaks free.
Surely he's had enough this time?
He starts to leave the box ...
... or is he?
One wonders why he is going now as the other bird seems to be out for the count and is on his back hardly moving.
No, he's not going yet!
The other bluetit is still on his back, not appearing to move.
Now this epic struggle really is over!
The remaining bluetit still seems completely exhausted by the fight. It has been in this position now for several seconds.
His opponent flies away. He clearly hasn't been too badly injured.
Another couple of seconds have passed and the victor still seems to be too dazed to get up.
Finally, after another four seconds he rolls over and stands up.
Another seven seconds passes and he jumps up the the exit hole to have a look out ...
... and leaves.
So what can we say about fights between bluetits?
First, they don't appear to do each other any permanent damage. Having now seen nearly a dozen fights, I cannot recall any that caused either bird to be injured. This must be good for the survival of the species.
Second, the winner often appears to be the bird that bloody-mindedly just refuses to leave the fight before the other does. I presume the current box owner has more at stake and so is likely to last the longer. That's why getting ownership of a possible nesting site early is so important. Hence all the time-wasting procedures that the birds get up, like taking nesting material in and out again and pecking at the walls and entrance hole, that keep them in or around the nest box while waiting for Spring to arrive.