Is a postdoc-interview presentation a norm? I have been invited for a postdoc interview. After reading some questions and answers, I noted that sometimes the applicant is required to give a presentation/talk. In my invitation, nothing is mentioned about a presentation or talk during the interview. Now I am not sure: should I prepare a presentation because it is the norm? 

(Of course I have some presentations from my previous talks/conferences. I just have to review it and do some changes.)

Edit: after a short email, they replied that presentation is not needed
At least in my field and country, giving a talk about your previous work is pretty common for the hiring process of any academic position. But that does not mean you should prepare a talk.
Nobody can seriously expect you to know this and automatically bring a talk to a job interview just because it’s the unwritten norm (and you probably do not want to work with the people who do).
Moreover, it is impossible for you to deduce the desired length, audience, scope, and other aspects of the talk.

Instead, you have to estimate how likely it is that this aspect was just forgotten in the invitation (e.g., going by the other details it contains).
If you think that there is any non-negligible chance that this is the case, just ask them.