Clover, green manure and the chicken run

Hi All

I have an area of ground that just doesnt seem to want to grow grass, its within the run, but I fence it off.

So I thought about Green manures and was told I could plant Field Beans & Forage Pea at this time of year - but the company didnt know if these were okay for chickens to forage around

The idea is that I sow something that will supplement the grass, in spring, something that will grow quicker than grass and still be okay for chickens to eat.

I've been told that clover is good, but not to be planted till spring.

After chickens have been confined on an area for a while it may not support vegetation for a few reasons.
First they compact the soil making it difficult for roots to penetrate. concentrated feces messes up the soil's pH and leaves it high is phosphorus/phosphates and salts. Ideally you could remove the top layer and replace. Barring that, you can cover the area with compost and plant in that.
What is your climate?
You can probably still plant the clover. It will sprout in the spring.
I don't use grass for the chicken's area since they don't tend to eat it unless it is a tender new shoot. If they ate all the tender new shoots, no grass would mature to where it could sustain a ground cover.
For pasture, I always plant alfalfa (hard to establish but hard to kill). I also use beets, radish, turnips, peas, wheat, oats and in summer - buckwheat.
With time, even those areas they've been on can be converted and support pasture.
The beans and peas are great forage (not the uncooked or unsprouted seed)

Here are some good charts on sprouting temperature.

http://tomclothier.hort.net/page11.html

If you have a short window, like it's cold now but several warm days coming, you can sprout some seeds in a bucket indoors and spread them after their roots have emerged.

But why isn't the area growing grass? Too much shade? Too much compaction? Chickens gobbling up the seedlings?

The forage crops sound safe enough, but if you can't grow grass, you have a good chance not being able to grow much forage.

I have found with our own garden/chicken rotation system that the compaction is only surface deep, assuming that the ground was not compacted to begin with and the chickens were not on it for more than a few months.

In answer to your first paragraph - all of the above.
If you have a lot of shade, grass has a lot of trouble with that as well as compaction. Between the two, there isn't enough solar energy to get the root past the compaction.
Even without chickens grass seed producers say one must rough up the surface for the grass to take. I like to cover those areas with compost to keep the seed moist enough to take hold.
Really, regardless of the seed, it needs to be protected and remain moist enough to sprout and for the tap root to access better moisture and nutrients.