Blue tits acting strangely!

Hello all

I don't know anything about birds and their behaviour so would really appreciate your help and advice.  We are used to seeing many blue tits in our garden, they particularly like our Berberis.  Since yesterday afternoon, two blue tit chicks have been pecking on the window pane and flying around the window, seeming to us like they want to come into the house!  I have read that birds sometimes peck at the putty around window frames but these two birds do not appear to be doing this, they are just flitting about the window and then pecking on the actual pane. We're worried that they may be in distress, why might they be behaving like this and is there anything we can do to help them?

Thanks

Jo