An unusually large flock of crows

I had my windows open at lunchtime and so I heard the start of a tell tale racket of bird calls. I sensed it might be the crows who often gather in the trees in the rear gardens, and then also flock at dusk to roosts nearer the centre of town. Thousands are known to gather in and around Stratford Park at dusk and it is a an amazing sight.

But at lunchtime it is unusual to hear so much calling by the birds. I looked out and saw a mass of corvids flying at various heights, some of them swirling and climbing high in the air. My camera was on my desk so I quickly tried to focus on the ones flying nearer the valley bottom as pictures of them against the sky don’t have much context. 

It was hard to focus as I wasn’t really sure how distant they were. I now guess that the ones in this picture are about three hundred yards away. By this time they were all flying away down the Golden Valley towards the centre of town about half a mile away. You can just make them out against the meadows on the far side of the valley. I’d estimate that there were probably many hundreds of birds when I looked right up in the sky and down the valley, but by the time I’d got my camera ready many had flown out of my sight. 

At the time I assumed they were flocking either for fun, or more likely as a defensive manoeuvre against predators. We have at least four buzzards that reside in the woods around the various local valley sides, as well as several sparrow hawks and more occasional visiting red kites. But when I see those birds they usually get successfully mobbed by just a small group of covids, such as crows or jackdaws. This mass was a of an =other order of magnitude. However I can see one buzzard flying over the far treetops, so there may be many more present in the scene.