The following was written and recorded by E.C. Jaeger in 1922. I believe, although dated over 90 years ago, this behavior is just as relevant today as it was then, however scaled down from our increasing intrusion into their ever-shrinking habitat.
If a female road-runner is approached when on the nest, she generally remains quiet until the intruder is right upon her; then she slips over the back of the nest and flies a short distance to safety, but where she can still see the unwelcome caller. At times she has been known to permit herself to be caught rather than forsake her young.
A member of the Cooper Ornithological Club (Mr. J. R. Pemberton) gives a most interesting report concerning the actions of a female roadrunner whose nest he found some ten feet above ground in a sycamore tree. As the observer began climbing up to the nest, the bird hopped to the ground.
“Immediately,” says Mr. Pemberton, “it began to squirm, scramble, and drag itself away across an open space and in full view. The bird was simulating a broken leg instead of a broken wing! The bird held its wings closed throughout the demonstration, though frequently falling over on its side in its enthusiasm. The whole performance was kept entirely in my view, the bird gradually working away from the tree until it was some thirty-five feet distant, when it immediately ran back to the base of the tree and repeated the whole show. I had been so interested up to now that I had failed to examine the nest, which, when looked into, contained five young probably a week old. When I got to the ground the bird continued its ‘stunt’ rather more frantically than before, and in order to encourage the bird I followed, and was pleased to see it remain highly consistent until I was decoyed to a point well outside the grove. Here the bird ran suddenly away at full speed and in a direction still away from the nest.”