Here you can see the setup with the pyrex glass trays and the glass jars. As the pigeons drink, the water level in the trays drops and water bubbles out to fill it back up. You can also see that there are normally two lightbulbs to keep the water from freezing. Since it is summer, Craig has removed the top one. Then he doesn't have to worry about accidentally breaking it.

He uses a variety of light bulbs with different wattages. If it is really cold he will put in a bulb with a higher wattage. If it is warmer, then a very low wattage bulb will do. Usually these range between 15 and 40 watts. We go through a number of light bulbs during the year, but it is worth it to not have frozen water every winter day.