Magpie behaviour

I saw a strange thing the other day which has me baffled. I walked round a bend on a path between bramble bushes; the path was grass by the way. As i rounded the bend I could hear a Magpie and to my surprise I saw what I thought was one Magpie lying on the grass on it's side,  quietly squawking. I thought it was injured and so tried to get closer thinking to myself what do I do about an injured Magpie!

Anyway, as I got closer the Magpie became aware of me and immediately flew off (with a bit of a struggle really!). However it wasn't one Magpie but two! I assume they were a breeding pair. I have never seen this before in all the time I have been watching birds (never mind how old I am Stuck out tongue winking eye) and wonder if anyone else has seen this beforte.

The only thing I can think of is that they were anting. The path was short turf which I believe is a nice environment for ants?

Anyway its nice to know there are always surprizes round a corner!