I have a hen that is acting quite weird. All the rest of my hens are acting normal. She on the other hand is pacing back and forth along a fence line then goes into the hen house walks to the corner of it and then goes out and paces along the fence in the chicken run again. She does also however jump up into her nesting box and then immediately jumps down and does the cycle all over again. She seems so agitated making a worried sound as she does this. What's up with her? Anybody have a clue?