I put the bulb in a heat lamp with a shrowd, and keep it about a foot above the water. It wasn't to keep the birds warm.That was a few years ago, when we had decent winters, in way upstate NY. The last couple winters I didn' t have any birds, and most of our winter was below zero with many days having -25 windchill. This winter is supposed to be justas cold if not colder. Maybe I should look into a bird bath heater. The rubber bowl is great also, when ever the water does freeze, the ice block falls right out.