This is one of the most underrated abilities. I advice everyone to do this:

Pick a bird that is common in your country or other areas you visit. Learn it's song. Soon you'll start to hear it everywhere and begin noticing variations around different locations. I did this with the chaffinch.

It's really funny to hear their dialects. Now, I'm definitely not skilled enough to pinpoint a bird based on its accent. But I do notice differences and it is thorough enjoyable, every time.