these are the oil filled heaters several have mentioned, my gram uses one in the house and they sound good because they are totally sealed and many have an automatic shut off is there would be a problem.
http://www.nextag.com/electric-oil-heater/search-html
Do you use the deep litter method in the coop? That is supposed to help with the heat as well. Would it be possible to put the birds in all together or make their pens smaller? Good luck, the lowest its been here so far is the teens here. I wrapped one wall completley in plastic because it was letting in a draft and it helped tremendously.
http://www.nextag.com/electric-oil-heater/search-html
Do you use the deep litter method in the coop? That is supposed to help with the heat as well. Would it be possible to put the birds in all together or make their pens smaller? Good luck, the lowest its been here so far is the teens here. I wrapped one wall completley in plastic because it was letting in a draft and it helped tremendously.