The snare in this case was the Virginia Stickseed, Hackelia parviflorus. This native plant is not particularly showy at any time of year, it often goes unnoticed until you discover dozens of sticky little seedpods covering your clothing.
The Field Sparrow was held firmly by multiple stems of seed pods running the full length of the left wing and half the length of the right-wing. My camera was already on when I came upon the trapped bird, but I only stopped long enough to take two quick shots of the incapacitated animal before rendering aid. It remained amazingly calm as I wrapped my hand around its body and snipped the seed stalks away from the plant. You can see in the photo that it had already lost two feathers in its initial attempt to escape entanglement. I was responsible for the loss of two more as I carefully cleaned away all traces of the offending seedpods. The entire cleaning process took about a minute, after which the bird flew from my hand, showing no signs of trauma or injury.
These seedpods are vicious little things and are probably my least appreciated of all the various vegetative hitchhikers. Caught up in cotton gloves or socks, they can sometimes be nearly impossible to remove. I know the Field Sparrow would never have escaped on its own. It was nice to find this guy while he was still healthy and sound, instead of long dead and dried as was the condition of previous sticky bur victims I have encountered in the past.