Why so many Crows???

I usually have 3 or 4 resident crows in the trees just beyond my garden...they are like the neighbourhood watch..If there is a buzzard or10 they go crazy allerting the neighbourhood.

However today I heard them and I always go and look just incase  I can get a good pic of bird of prey

God when I looked out the window my 3/4 had boomed to about 40/50

I no it dont look that many but if you zoom in you will see them all

I had to go outside...the noise was intense!!

i was surrounded

Surely they hadnt all gathered to salute the flyby Geese!

Well it was an intense 20 mins or so before they all dispersed and it all went quiet

Any ideas why so many gathered...there was no fighting, no bird of prey that I could see either