Have you ever seen a Common Kestrel fly very, very high during migration? And if so: have you ever seen small parties or groups - 4, 7, 10,... - migrating together ?
I am talking about 500+ metres above the ground, so high that you could either only barely spot it with your unaided eyes - or - that you only accidentally discovered the bird waaay up high in the background of another soaring raptor/bird you were looking at with binoculars - or - in the middle of a kettle of soaring/migrating buzzards you check with your binoculars, so high the kestrel itself is not discernible by naked eye only?
I can't recall a single situation where this happened to me, but that could be old age or prolongued fatigue. Which is why the field experiences of others are important for me to find out.
The cast in alphabetical order:
Common Kestrel, Falco tinnunculus, Turmfalke [tower falcon]