Watching Migratory Birds

Lately, I have been seeing many migratory birds at home... and even in the Office conference room (there's a small park outside the glass wall). Guess it's really cold from where they come from and they seek a place to stay until they could return. How do they figure out when to go home?  

Anyway, it's nice to see other species of birds aside from the regular sparrows you I everyday.  It's a good thing there's a tree right in front of our door. Once in a while I see a different bird seeking shelter and saying hello.

I hope that the future generations would still see birds flying around freely just like today.  Let's protect our forests that serve as shelter for these birds.