Observations after one week on pasture

One week after being introduced to their new pasture, the chickens have scratched up perhaps a fifth of the area to bare soil.  I estimate that this pasture is about 700 square feet, so our chickens are at a stocking density of 140 square feet per chicken --- amazing that they can make such a large impact in such a short time!  The bare minimum pasture standard would keep them on this pasture for 14 weeks, but we'll probably rotate them to a new patch of ground in another week or two.  I want the flock to do a little more damage first, though, because I have plans for those patches of bare ground.

I was a bit concerned that so few birds in such a large pasture would spend all of their time sitting beside the coop.  So I had Mark install the gate at the opposite end of the pasture and have been feeding the chickens their morning rations, food scraps, and wheelbarrow loads of weeds right inside the gate.  This has split the chickens' interest, and they seem to spend time pretty evenly throughout the pasture (and always come running to the gate when I get close.)  I wonder how big a pasture would have to be before chickens would ignore the extreme edges?