I know this is an old thread, but I found it when searching for this exact symptom! Beekissed - We have a Delaware hen that does EXACTLY what you described your White Rock as doing! I usually notice it when I am feeding them in the morning in our coop. She will duck her head in an exaggerated motion and then scoot backwards several feet, like she is trying to avoid the other hens, even though none of the other chickens are near or even paying attention to her! It is very weird! She also is the only one in our flock that seems to have a (possibly unrelated) diarrhea problem. BUT, in a recent 5 day egg watch, she was one of our best layers, laying 4 eggs in 5 days!
Has anyone found any more information on what this strange "bowing and scraping" might be, or any nutrients or supplements that might help treat it?