What is the difference between
Such behaviour
and such a behaviour?

cheers

Such behaviour = several behaviours from an individual.

Such a behaviour = one behaviour from an individual.

That would be my take on this.

I think that “such behaviour” is using behaviour the uncountable noun whereas “a behaviour” is using behaviour as a countable noun.

That’s off the top of my head, I am willing to be corrected.

Such behaviour

Your general demeanour, attitude and comportment

and such a behaviour?

the way you behaved in a specific incident / set of circumstances. This is far more speciic and relates to either one incident, or the repeated demonstration of a specific behaviour when subject to the same conditions

I think, anyway.

A – you’re native
B – you’re johnny foreigner or camp