Examining a sick chicken? Help?

[jennyf]

Can anyone point me towards a resource for examining a chicken? One year old GLW, just went out to toss some meat scraps, rest of flock dove on them but she didn't. Picked a bit at some scratch but also not typical chowing down. Good poops on the poop board last night, not certain if she laid an egg today. About to go out and catch her, figured I need to check crop but I don't know what else. No respiratory issues, walking around a little but not as active as usual. Other five girls seem great. This is her posture, if it's helpful.