Momma can't "smell" if someone has handled it. That's just a silly myth. In truth, birds have no sense of smell (although Vultures can smell somewhat, to locate food). But the songbirds we see in north Texas (Bluebirds, Wrens, Cardinals, Robins, Titmice etc) just can't smell at all.
So pick up the bird if it's absolutely necessary. But don't "kidnap" it. Keep in mind that the vast majority of the time, a "fledgling" bird is being monitored carefully by a parent in a nearby tree. Most young birds spend around a week on the ground, still unable to fly, after emerging from the egg and growing larger and stronger.
If a human frequently goes and looks at it though, the human will leave a scent trail that a hungry predator (raccoon, snake??) can follow.
Ninety-five percent of Texas' Santa Ana National Wildlife Refuge (in the lower Rio Grande valley) was obtained through the purchase of "Duck Stamps", which are used not only for Duck habitat, but for acquiring habitat for all kinds of birds.