Hopefully the listing isn't gone by the time you read this.
IF I could get used to the idea of moving - traveling - with my birds in a 5th wheel, AND if I thought we'd be able to afford both a 5th wheel AND a new truck, THIS is what I would buy!
Already has bunks (ie, shelves) for bird cages in the garage, plus a window for light for them.
Has the side ramp which is ideal to convert to a small patio; the outside action happens on the passenger side of these when parked, not in the rear. I would also have a pull-down screen installed so that it would be open during the day when we're parked, for fresh air and natural light for my parrots to enjoy. It would be easy to take one (or more) of them outside (caged of course) with me as well!
Inside the "people part" of the unit is still everything I would want for our own living space. The kitchen is perfectly adequate, it still has a full bedroom (many of these have a double bed walled in on 2 sides), and it even has a small outside spot for cooking on hot days when we don't want to heat up the rig! And the heated enclosed underbelly is ideal since we will be spending at least part of the winters here in Michigan.
Yes, IF all of the issues (price/truck/birds remaining in the vehicle when it's moving) were resolvable, this would be the perfect fit for us, and I could definitely see us living here full-time!