When do birds flock in the sky?

I need to film birds flocking in the sky but I don't know when the best time is to do it. I don't know much about birds, I assume they come out in the evening from just casual observations.

I want to film from now (october) to November, its getting colder though so does that mean they don't flock anymore?

I realise the ignorance of these questions but I thought best to just ask the question simply.

Thanks in advance.

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