Tom's Bird Feeders and Reptile Supplies

By Bill Fintel, Avian Aquatics, Fall 2003

A. Goals of Winter Care:

There are two basic goals to keep in mind:

1. Providing drinking water for birds visiting your yard
2. Maintaining gas exchange in a pond containing aquatic wildlife. A bird’s need for drinking water becomes most critical as natural water sources freeze solid. Birds can use snow as a source of water, but often snow gets glazed over with ice and then it can not be used. The most critical situation arises when there is no snow cover, and temperatures remain below freezing for a prolonged period of time. When providing water via a bird bath, use a bath which will not be damaged if it accidentally freezes, and maintain just enough open water for the birds to drink.Gas exchange makes for a healthy pond by providing oxygen needed by fish, hibernating frogs, etc., and by discharging toxic decomposition gases to the atmosphere. In a pond that is completely frozen over, gas exchange is blocked by the ice layer, and with time aquatic wildlife under the ice can perish due to lack of oxygen or to toxic gas build up. Because chemical processes slow down considerably at low temperatures, only a small area of a pond needs to be maintained open for it to remain healthy. As a rough guideline, try to maintain a minimum of 10% of the surface free of ice during the coldest periods.

B. Energy Conservation

Throughout this guide you will find our discussions address maximizing energy conservation. In other words, using only the minimum amount of purchased energy required to achieve the open water goals of Section A. The three basic techniques to be employed are:

1. Minimizing heat loss
2. Maximizing gain from solar and geothermal energy
3. Optimizing heater and thermostat selection when they are required These topics are covered from an overview perspective in the following sections. In cases where in-depth coverage is warranted, they have their own separate category later on.

1. Minimizing Heat Loss
   The principles here are very fundamental. Just make believe you are the winter bird bath or pond and do what you would do to stay warm – get low to the ground out of the wind, curl up into a ball to minimize exposed surface area, and wrap a blanket around yourself. These principles apply to winter water sources as well.For example:
   • Choose a ground level bath over an elevated bath, as it has less area exposed for heat loss.
   • Locate a bath or pond on the south side of a wind break, such as a house, wall, fence, or shrubbery.
   • For large bird baths or ponds, float pieces of Styrofoam on the water surface to act as insulation. For esthetics, the Styrofoam can be painted brown with latex paint.
   • For ponds with creek systems or waterfalls, bypass these to reduce exposed surface area.
   1. Maximizing Solar and Geothermal Energy
      The sun and the earth can be major allies in your quest to provide winter water economically. The following principles are often easy to implement when planning ahead.
      • Locate the bath or pond in a location receiving winter sun
      • Choose a dark color bird bath
      • Design the pond circulation system to deliver warm water to the pond surface
      • Remember that ponds which go below the frost penetration depth probably will not require a heater
   2. Heater Selection and Use
      The key here is only use as much electricity as you need to maintain enough open water for drinking and gas exchange. You are on the right track if, when temperatures go below freezing, your winter water source has a combination of some open water and some ice. – Use the minimum wattage heater to get the job done (see details in Section E) – Be sure the heater is thermostatically controlled – Consider dual thermostatic control for maximum energy savings (see Section C on TMC). – Unplug any heater when temperatures remain above freezing.

   C. TMC Thermostatic Plug
   The TMC is a plug with an internal thermostat that operates based on ambient air temperature. This is different from thermostats in heated baths and submersible heaters which turn on and off based on water temperature. The TMC turns on at approximately 35° F and off at approximately 45° F AIR temperature. The benefit with this type of control is that as soon as the air is warm enough to be melting ice, the heater plugged into the TMC is turned off. This is especially beneficial for ponds where you might have a large volume of water which you just want at 32° F, but the submersible thermostatic heater you are using is set to warm it up to 45° F and indeed keeps consuming electricity until the water reaches 45° F. With the heater plugged into a TMC, the TMC will shut off the heater when the air temperature reaches 45° F and allow the air to continue the warming process.

   D. Choosing a Winter Birdbath

   1. Material and bath design
      A bird bath to be used in below freezing conditions should be made from a material and of a design that if it accidentally freezes, it will not be damaged. Most plastic baths with a relief to allow expanding ice to pop out of the bath are fine. Concrete and ceramic baths are usually a poor choice. Ground level baths are more efficient than elevated baths because they only loose heat from the top. Elevated baths, such as pedestal and railing mounted baths, loose heat from the top and bottom, plus they are exposed to more wind caused heat loss.
   2. Color
      Dark colors are preferred to maximize solar energy absorption. If placed in a sunny, sheltered location, such a bath will often provide drinking water around the edges even down to about 24° F. Dark baths with thermostatic heaters will consume less electricity.
   3. Built-in Heater
      A thermostatic heater installed on the underside of a bath is the most aesthetically pleasing type of heating arrangement because it does not take up space in the bath and is not visible. A 60 watt heater will keep open water down to minus 20 degrees for a bird bath with a water surface of approximately 12″ x 18″. Remember that you can save a lot of energy by using a TMC thermostatic plug in conjunction with a heated bird bath (see previous section C). Also remember to unplug your heated bath whenever the heater is not needed.

   E. Selecting a Heater for an Existing Bath
   If you are choosing a heater for a plastic bath, be sure the heater you select is suitable for plastic (most are). Your wattage selection ranges from 44 watts to 500 watts. All except the 44 watt heater are thermostatically controlled, and will not be damaged even if the bath runs dry.

   The following table is an approximate guideline for selecting a submersible heater to maintain enough open water for drinking in a nominal 14″ diameter pedestal bird bath, with a 2 1/2 inch water depth. For a ground level bath, the listed heaters will to be okay to another 10 degrees colder.

   Min Temperature	Wattage/Thermostat
   5° F	150W thermostat
   0° F	44W non-therm
   -10° F	200W thermostat
   -20° F	250W thermostat
   -35° F	500W thermostat

   Remember that you can save a lot of energy by using a TMC thermostatic plug in conjunction with the above thermostatic heaters (see previous section C). Also remember to unplug your heater whenever it is not needed.

   F. Pond Winterizing
   Consideration should first be given to reducing exposed water surface area to reduce heat loss. Waterfalls and shallow creeks can be a significant source of heat loss and in cold climates are often best bypassed to conserve energy. To bypass, simply take the hose loose from the waterfall or from the head of the creek, and place it on the edge of the pond to be kept open. Alternatively, disconnect the hose form the pump and replace with a short section going to the pond edge. Bring inside any pieces that will be damaged if allowed to freeze, such as a waterfall rock.

   Many ponds will not need a heater IF the pump is properly positioned to take warm water from near the bottom and discharge it at or near the water surface. This arrangement works as long as the depth of the pond is deeper than the frost penetration depth. Figure 6 shows the average frost penetration depth for regions of the U.S. so you can see if this approach will work for your pond. Even if it will not work all winter, it can still be utilized to minimize the amount of time a heater is needed, and hence reduce your electrical bills.

   When using a heater in a pond, again keep in mind that your objective is to deliver warm water to the pond surface to prevent it from icing over completely. To accomplish this, the heater can be placed just before the pump intake and the tubing from the pump positioned to discharge at the pond surface, or you can place the heater at the edge of the pond and discharge the water from the pump across the heater. For a pond with a creek, it is often easiest to just place the heater in the creek and let the water flow across it down into the pond (Fig 4). In addition to the submersible heaters listed in Section E, you can use a floating pond heater which by virtue of it’s floating design, delivers heat to the surface without a pump.

   G. Solar Winter Water Source
   The easiest material and least expensive to use is black pond liner. It will not be hurt if it happens to freeze, it absorbs solar radiation very efficiently, and with in-ground construction is easy to shelter from the wind. Unlike conventional ponds, you will want the liner at the water’s edge exposed to the sunlight. Then, even if the entire volume of water freezes solid overnight, as soon as the sun hits the liner-ice interface, if it is not too cold, the sun will start to melt the edge of the ice making it available for birds to drink. In a protected location and on a sunny day, melting should occur down to approximately 20° F with such a set up.

   H. Geothermal Winter Water Source
   If you are starting from scratch and very concerned with energy conservation, then this approach is recommended. The basic principle is to construct a reservoir that goes below the frost penetration depth. In the bottom of this reservoir place a pump to deliver water to the pond edge to be used as the drinking location. A 120 GPH pump should suffice and will only consume approximately 10 watts of electricity.

   We hope this article has provided some new insight into winter care of outdoor water features, particularly those used to provide water for birds. Your comments are welcome.

   Good winter birding!

   Copyright ©2003 Avian Aquatics Used With Permission