Darby's in the dog house :(

Well, I got a message on my answering machine last night when I came home from work, (I work second shift, 3:00-11:30pm). It was from the people 2 houses over complaining that Darby was barking and it woke them up last night.

Now, for a Collie, Darby really doesn't bark that much, but when he sees something going on around the block, he will voice an opinion. When I'm at work Darby has access to the back yard through a pet door, and usually he will curl up under his favorite pine tree or sleep on the porch, and when he gets tired of that he goes back inside and crashes on the couch 'til I get home.

At this point, the only way I can think to keep Darby from barking is to lock him in the house for 8 hours until I get home, which seems pretty sad. I've also ordered something from a catalog called a "Husher Elastic Training Aid", which is basically a looser-fitting muzzle designed to discourage barking. How I supposed to use this, though, I haven't quite figured out.

So has anybody else had a problem with inappropriate barking, and what did you do about it? Is there any chance I can correct this behavior, or is Darby going to lose his yard privilages forever? :(