One of my hens - she's about 6 - has not been returning to the coop at night for the last couple of nights. The first night it scared me since I thought something may have gotten her, although she's an awfully big girl for a hawk to get. The next morning she was up and about in the yard (our yard, they free-range). Then last night she did the same thing. What's going on? She doesn't seem to be acting any differently during the day but I can't say that with absolute confidence since I haven't done any long observations. I feel like something must be wrong. She's the number one or two (hard to tell sometimes) hen in the flock.