Angry birds?

I know it's an awful picture. The composition is non-existant and the colours are lifeless but I haven't a clue what those collared doves were up to so I took the pic.

The 15 on the ridge were fairly evenly spaced out and making a racket every time one of the three on the guttering tried to join them. It became quite violent with a bit of pecking and wing beating and went on for about 5 minutes then they all flew away.

Now what was that all about?