the concern is that often electric heaters with a coil are coated with chemical that can overheat and cause deadly fumes for birds. It's PTFE (polytetrafluoroethylene) sometimes called Teflon. I think there are other types that also emit toxic fumes when overheated. So, you could be using one that has this unsafe chemical coating on its element and not even know it till one day your feathered babies are dead. It only takes a scratch on the coating or overheating to emit the fumes and within minutes it will kill birds and you won't know it's happening. unfortunately it's hard to tell what has this chemical coating as it's not always labeled. I use the electric oil radiators so I know there's no chance of my birds coming in contact with these chemicals for the same reason I got rid of all my Teflon cooking pans. Often you can call the manufacturer and get info on it. good luck! I found two of my oil radiator heaters used locally for $35 (for both) so they are not expensive and work well. Make sure your bird cannot get too close, kids too. They do get HOT