I'm surprised I am the first to add this in, but this past summer I was having problems with ants coming in my run to get the chicken feed. I was worried about putting poison down for obvious reasons and so I asked around. I had a friend who has had chickens for years and years and year give me this advice: scatter some coffee grounds around the pen and the ants will become a problem of the past.
I was hesitant at first but followed directions and it worked. no more ants and as long as I didn't spread the coffee grounds in front of the chickens (so they though I was scattering a treat) they didn't eat it, and even when I did they would peck at it a little then leave it alone.
I hope this helps someone