I don't know if you have them but I have a huge mulberry tree right over my coop and area where my run will be.
http://www.fao.org/ag/aga/AGAP/frg/Mulberry/Papers/HTML/Mulbwar2.htm
http://www.fao.org/ag/aga/AGAP/frg/Mulberry/Papers/HTML/Mulbwar2.htm