Most of us who own bird dogs also own a truck to haul them around in. But dogs left to their own devices in the bed of a truck will always find a way to get into trouble. At best this can be an inconvenience; at worst it can cost you big money in damaged equipment or vet bills. Either way, it makes sense to avoid problems before they have a chance to begin.
First, you'll need a crate. This can be a store-bought plastic airline crate, a wire mesh crate or a homemade wooden box, but you've got to have something to confine your dog so he can't roam at-will in the back of your truck. If you're good with tools building a box is an easy matter, but it can be tough to ventilate. For not a lot more money you can buy a plastic or mesh crate. Both are lightweight and durable and will help keep your dogs cool in hot weather.
In cold weather, you'll have the opposite problem: keeping your dogs warm. But there's an easy solution: insulated crate covers. The good ones aren't cheap but they'll last for years, and you'll be amazed at how warm they keep your dogs when they're zipped up (leave them open at the bottom for ventilation). Just remember to take them off in the spring when the weather warms.
Overweight dogs can blow out knees jumping from the bed of a truck to the ground. If you've got a small dog- — say a Brittany that weighs 35 pounds — letting it jump into and out of your truck probably won't present a huge problem. But with a large dog, like a 70-pound Lab, a jump out of your truck is a torn ligament waiting to happen. Either get in the habit of lifting your dog out or buy one of the commercially made dog ramps, which will fold up and store out of the way when not in use.
Never, for any reason, let your dog ride loose in the back of an open pickup bed! Farm dogs have ridden this way for decades, but even well-trained dogs — those that won't succumb to temptation and jump out when they spot something interesting alongside the road — can lose their balance on a sharp corner and fall out. Hundreds of dogs are killed or maimed in this way every year.
Put your dog inside with you or in the back in a crate that is securely latched in place so it can't slide around. Doing so will ensure that your buddy has a safe, happy trip and arrives at your destination in good shape and ready to go.