Chicken laying seldom, thin shelled eggs

[pasesak]

I have 4 hens and one rooster, all free range. The alpha hen, Henny, is a vicious and angry hen. The other hens all lay normal, beautiful eggs. Henny, however, for the past 3 month or so has been very peculiar. She used to lay such beautiful enormous eggs, the biggest of my flock, but then weirdness struck. First, she was still laying in the nest box, but most of her eggs would be smashed or cracked, and thin shelled. Then, she stopped laying in the nest, and started laying her thin shelled eggs in the grass and cement, still cracked and smashed. She would lay every other day before it seemed. Now, she is down to about once a week, if I can find them. I don't know what is up with that chicken.

Some other info: the hens have ample supply of water, feed, and oyster shells. I live in Hawaii, and in the winter at this elevation it gets down to maybe 50's at lowest. The hens are only 1 year 5 months old. The hens are missing some feathers, 2 have completely bald backs, not sure if from rooster or molting, but they have been missing feathers for 6 months now, not growing back. The hen who is the problem layer is not bald backed. She acts almost normal, except that a couple of times I caught her climbing into the nest box and just hanging out, even though she doesn't lay any eggs. Doesn't strain or act hurt, she just sits there.

What could be wrong, and what can I do to remedy the situation?

 

[delynnel]

How old is Henny? If she's a hatchery layer then her laying cycle will only be a bit over a year long. Usually if they're thin-shelled eggs it's a calcium issue but you're giving them the right food... maybe she needs an extra supplement?

 

[pasesak]

Henny is 1 year 5 months. She is a RIR. Is that considered a hatchery layer? I am a chicken novice.

 

[delynnel]

some chicks that you buy from hatcheries are genetically modified to be better layers and only lay for a year. If it's a purebred RIR then it should lay a bit longer but the first year is the prime laying year, so it would taper off a bit after that. RIR's are good for eating after their laying cycle is finished, good "dual-purpose" birds

 

[Pinky]

Does she stay in the nest box almost all day? She may be broody.