A tractor is a small mobile pen that is used to contain poultry but allow you to move them around on a daily basis. Lots of people use them in gardens or free range areas where they just can't let the birds loose for whatever reason. Some tractors I've seen have small wheels in the back and handles in the front that make it easier to move. Mine is on skids and I just pick the front up and pull it around. My gambels got good enough that they would get up on the skid and ride while I pulled them to a new location. Before they learned to be such good riders I had to go real slow and careful to keep from getting their legs caught and pulled under the tractor.
Here's a really fancy one, most are no where near this fancy
http://www.pallensmith.com/newsletter/mailbox_java/mailbx_110802a.htmWe do get a lot of rain in the winter and spring around here but in the summer we can get real hot and dry.
I also would not advise mixing your quail. The gambels I had can get real aggressive once they reach sexual maturity. They turn into little butcherers. Mine were ok as chicks but I had to get them separated after a few months when the problems started.