[Nancy1999]

First of all, this is a Yorkie trait, they are barkers, and are trying to warn you of any intruders. My living room overlooks a park, and Joey's favorite place is on the ledge of the couch looking out the windows. He loves barking at people, but it got to be excessive. The coins in the can worked for me. I just put coins in a thick tin can with a lid and shake it, and say "no", or "shhhh" and this usually stops the barking. I also bought a Bark Repeller for other times, such as when a workman comes to the house, the coins didn't help at those times. The bark repeller works by emitting an annoying sound only dogs can hear, and I use this in conjunction with the word "shhhhh" with my index finger up to my lips in a shushing fashion. Again, you will not eliminate barking, and this should not be the goal, but you will reduce it significantly. The other option is to put up a window covering so they can't see out.

Cesar has shown a positive reinforcement method where you have someone walk by the windows and you reward the dog by going into the alpha state, other trainer will reward the dog through food, but only when it displays the calm non barking behavior. You probably can't do this with the windows in your building though.