different dialects?

Had another good day around the reserve today, despite some drama with a grass fire. Lots of birds singing all around and though nothing unusual appeared I still saw 21 different species.

One thing I noticed was the difference in the calls and songs of some of the birds from what I hear at home with birds of the same species. Most noticable with blackbirds and the great tits. As I only live about 40 miles from the reserve I'm suprised that there's a big difference.  Any body else noticed this?