There is nothing more placid than a Lab...
...which is why people don't use them for high-desert quail. That and their warm coat, which isn't exactly ideal for it. And try finding cholla spines in it.
Would a Lab Retriever keep up?
No way, no how. Nothing against labs, but that's like asking if it can outrace a greyhound.
We have a Vizsla. He's a pup, not hunting yet, but I can tell you he is completely different from a Labrador. He can already go for miles, at running pace the whole way, without stopping. I run for three miles, and he runs circles around me, up hills, down hills, ahead, behind, never stops. Then he wants more. He gets cold easily, but he has no undercoat and a very thin coat and doesn't overheat easily. He was born with the ability to point and "hunt-em-up" is what he naturally does when you turn him loose. Retrieves and swims fine, too.
Labs for retrieveing. Pointers for pointing. Spaniels for working cover.
Or just get a versatile hunting breed and it will do all of those things just fine. Only thing a VHD doesn't want to do is sit still in a cold duck blind. That's what Labs are for.
http://www.navhda.org/
Don't get me wrong, I like Labs. I'm a big fan of my overly-affectionate, super-athlete 35 MPH Pit Bull Terrier, too, but she won't ever be a bird dog. She has beaten labs in swimming and dock-jumping competitions, but she's a bit hard-mouthed.
Different dogs are bred differently, and are built differently. They have different muscle fiber type ratios, different tolerance for cold/heat, different coats, different levels of endurance, different mindsets, different abilities.
I've seen a Lab or two on a trail here in the heat. My wife and I once risked our own health hiking in the hot sun by giving all the water we were carrying to someone's Black Lab, which looked like it was near collapsing from dehydration and heatstroke. Damn irresponsible dog owners piss me off. It's up to humans to use our judgment; our loyal dogs will follow us just about anywhere, even if it kills them.
Be VERY VERY careful using a Lab as an upland dog in the desert sun! Or just don't do it.