The Lincolnshire Bird Club

Not sure where this topic belongs - doubtless someone will tell me.

I also hope someone will tell me:
Q1 Why Bitterns at Far Ings don't move out in hard weather?
Q2 Do the Bitterns that move in to eg Boultham Mere then move out in hard weather?
Q3 Presumably the Bitterns that move in to eg Boultham Mere stay there for the winter - i.e. they are site faithful for the winter - and maybe even from one winter to the next?
Q4 The Med Gull at Chapel Point has returned for many years - but other Gulls appear to stay for only a day at eg Leadenham: why the difference?
Q5 Stuart Britton has reminded me of the terrific turnover in eg Blackbirds at some of his ringing sites. Yet some species eg Robins are site faithful and even sing in the winter. Why the difference between these species?
Q6 Related to this: I noticed some species eg Western Olivaceous Warblers singing loudly and frequently from the same trees in The Gambia in the (northern) winter and they are presumabably holding territory and are site faithful??
Q7 Hardest of all for me to understand is whether these hard weather movements - or the lack of them - are examples of genetic or learned behaviour. Does anybody know?

Thanks,

Rob