Flock size

Morning,

Sitting out on the north side of the house a few days ago, I noticed a flock of around 800 birds flying west in a relatively tight, ball-shaped group.

With the exception of Starlings, around water (so, Lapwings for example), swifts, or passerine invasion years (Bramblings), I've rarely seen such a big group.

I know that I'll never know what these birds were. They were flying away from me; bins were in the house. But I had the impression I was looking at medium-sized waders.

This was steady, powered flight, around 2 to 3 beats per second.

Anyone know anything about migration habits and flock size?

For those who don't "know" me, we're situated in the Swiss Jura hills. So the birds were flying toward Franche-Comté, and were just a few kilometres from the three-lakes region of north-west Switzerland, and the country's largest uninterrupted wetland/reed-bed zone.

Best regards - 

Dave