Do chickens really need light to lay in areas with long winter nights?

This post on Solar Lighted Chicken Coops reminded me that my chickens aren't supposed to be laying eggs now.  But they are.  A huge caveat is that I'm new to chickens so I don't know what "normal" is yet.

I have 11 hens from local homesteader parent stock that were hatched this past spring.  The last two weeks it's been rather cold (highs around 5F) and the days are pretty short (9 hrs from sunrise to sunset).  I've been getting 4 or 5 eggs a day.

So are my chickens broken and giving eggs when they aren't supposed to?  Or have the breeding skills of the chick providers really developed a chicken that can handle the cold?  Do I have something amazing here or is it just normal?  If it's just normal, what more could they do with an extra couple hours of light?

For added information, their coop is darkish wood interior with 4 windows (I'd say they have an average amount of natural light in the coop).  They have a pleasantly warm hoop house to hang out in during the day.  I'm giving them all-they-can-eat organic feed and supplementing with a cup of wheat as a snack each day.

I would be delighted if my chickens were laying right now. The thing is, there is no right or wrong or normal. Your chickens laying in the dead of winter is normal for those chickens. When we read about chickens not laying during the short days of winter, it's based on what seems to be common, but there are always exceptions. I wouldn't bother with adding a artificial light in the coop. Your chickens aren't "broken"

Some breeds are knows to be better layers in the winter than others.

FWIW, my Black Austrolorpes haven't given us any eggs (at least in the coop - we do let them free range for some of the day most days) in several weeks.  But they're also getting close to 3 years old.  That may be part of the deal too.  Younger chickens will lay more all else being equal.

I'm a lot further north than you (57N)and some of my chickens have been laying all winter, some stopped in November and will not start again untill March, in my experience it depends on the breed, hybrid layers will almost certainly carry on all winter, you may or may not notice any change, but my old breeds, Marans, and Landhøns stop when the daylight drops under about 10 hours. (we get 4-5 hours in december here) Last year I gave the old breeds light and they laid all winter BUT because the weather is terrible they lurked in the coop and developed bad habits such as egg eating, so this year I left as is and let them sleep 18-20hours a day, no time for bad habits!

If they are laying great! It won't do them any harm either way, I stored a ton of eggs this year in the freezer expecting no eggs, and then my new three mutt hens have decided to lay all winter anyway.

Thanks everyone!  I did some more searching (should've done that first) and found that young chickens are more likely to lay through their first winter.  Plus mine are hybrids.  So I guess it's relatively "normal".  No lights for me :)   And it gives me one more reason to let a broody hen raise a batch each spring to keep the flock young.

For me, being at nearly 49 North, our days are too short for the chickens to eat enough food, so they get weakened and sick easily.  This is why we put the solar lights in the henhouse.  It's helped keep them healthier this mid-winter and last to have 8 hours of daylight instead of 6 (or less when it's cloudy).  I don't think it's improved egg production much.  For 20 hens, we get about 4 eggs a day in the winter with our without lights and about 18 to 21 eggs per day in the summer.  But my girls are a couple of years old now, so we will be hatching out some more chicks this spring.  

I wonder if I brought the light up to 10 hours a day if this would help them more.  My solar system only allows so much, but I'm looking to add a wind and small hydro (rain) generator to the system.  

My experience is that light has little to do with egg laying (sort of). The number of eggs a chicken lays depends much more on how much food they eat (plus in winter they need more food to also stay warm). If chickens get enough food, they lay year around. Adding lights in winter just gives the chickens more time to eat, ...so they lay more.
P.S. You mentioned the coop interior is darkish wood. I suggest you paint the inside of the coop with whitewash (simply mix hydrated lime with warm water and "paint" it on). White walls reflect light better so coop will be "lighter" inside, giving the chickens more time to eat. Also, the lime in whitewash tends to kill bugs, while not hurting the chickens.

Good tip Jim, I'll think about the whitewash.  In retrospect, it's not all that dark.  It's basically raw pine boards.  They're pretty so I'm not sure I can get the missus to agree to a whitewash but we'll see.  The birds have unlimited food and plenty of time to just sit around so I hope they are filling their bellies....