Two different questions get answered as one every winter, and they have different answers. The first is whether birds need open water in freezing weather. The second is how to keep a bath liquid if you decide to provide it.
We are going to take them in that order, because the two most authoritative sources in American backyard birding do not agree on the first one, and that is worth knowing before you buy anything.
Do birds actually need it
The Cornell Lab of Ornithology is the more cautious of the two: "Birds will come to birdbaths year-round. Fortunately, keeping a birdbath ice-free in winter is not critical. Birds have several physiological mechanisms for conserving water, and can usually get what they need from snow or dripping icicles."
The National Audubon Society reads differently. Their winter guidance states plainly that "many kinds of birds bathe in and drink from open water in frigid weather," and goes on to recommend buying a heated bath or converting an existing one, with no equivalent caveat. University of Nebraska Lincoln Extension is firmer still: "A fresh, unfrozen water source is as important to birds in the fall and winter as other seasons."
That is not a factual contradiction so much as a difference in framing, and we would rather show it than pick one. Our own reading is that winter water is a good thing to provide and not a rescue mission. If you enjoy the birds it brings, run it. If you are away for three weeks in January, Cornell is telling you that the birds will be fine.
The part with no disagreement at all: put nothing in the water
Every source lines up here, and the wording is unusually blunt for organizations that normally hedge.
- Antifreeze
- Cornell says to "never add antifreeze to a birdbath" and states that it "is poisonous to all animals, including birds." This is the one that kills.
- Glycerin
- the folk remedy that circulates every December. Cornell: "Don't use glycerin, either: it can saturate and mat a bird's feathers leaving it susceptible to hypothermia." Project FeederWatch adds a second mechanism: "Glycerin is a low-level toxin and has a sweet taste. Ingesting large amounts of glycerin elevates the blood sugar level of a bird, which can be harmful or even fatal."
- Salt
- we looked for a bird organization or extension service that addresses salt in bath water specifically and did not find one. What we found instead was guidance about salting walkways, which is a different question. So we cannot cite anyone on this. We would not do it, on the general principle that a bath is drinking water, but that is our position rather than a sourced one.
Read the glycerin warnings together, because they are the interesting pair. One is about ingestion and one is about the feathers. A bird that gets glycerin in its plumage loses the insulation that keeps it alive at the exact temperature you were trying to help it survive. The remedy makes the problem worse in the specific case it was meant for.
What works is a heater, and here is what the sources actually say
- Built in
- Cornell: "manufacturers now offer birdbaths with built-in, thermostatically controlled heaters."
- Immersion
- Cornell again: "Immersion heaters are also available at most places bird feeders are sold. Most new models turn off if the water in the bath dries up." That dry-run cutoff is the feature worth checking before you buy.
- Converting one you own
- Audubon suggests buying a plastic bath with a heater built in, or adding a heater to a summer bath.
- Running cost
- Project FeederWatch says these heaters "cost pennies a day to operate."
Now the honest gap. We went looking for a wattage figure from Cornell, Audubon, an extension service, or a federal agency, and there is not one. Every wattage number you will read online comes from a retailer or a product listing. So rather than repeat a number we cannot stand behind, here is the arithmetic to run on whatever unit you are looking at.
- Take the wattage from the product label and divide by 1000 to get kilowatts
- Multiply by the hours per day it will actually run, which is not 24, because the thermostat cycles
- Multiply by the number of days in your freezing season
- Multiply by your electricity price. The US Energy Information Administration reported an average residential price of 18.44 cents per kilowatt hour in May 2026
Do that once and the answer will usually land somewhere between a few dollars and about twenty for a season, which is what the FeederWatch line means in practice. The point of doing it yourself is that you will find out whether the unit in front of you is one of the cheap ones or one of the expensive ones, and no article can tell you that.
The electrical half, which almost nobody writes about
You are putting a mains powered device into standing water in the open air. This is the one section of this guide where getting it wrong is not a bird welfare question.
- The outlet
- the National Fire Protection Association states that "All outdoor receptacles should be GFCI protected." If the outlet you are planning to use has no test and reset buttons and is not on a GFCI protected circuit, that is the thing to fix before anything else.
- The cord
- NFPA guidance is to use extension cords that are listed by a qualified testing laboratory and marked for outdoor use. Not an indoor cord run out through a window. The Consumer Product Safety Commission draws the same line, distinguishing "cords intended for indoor use only" from "cords intended for both indoor and outdoor use."
- The run
- keep connections off the ground and out of standing water, and do not chain cords together. That last one is our own practice rather than a citation.
If you rent, or if there is no GFCI outlet within reach of a proper outdoor cord, that is a real answer rather than an obstacle. Skip to the manual methods below.
The part where our own product is the wrong choice
We sell concrete bird baths, and this is the section where we tell you not to use one.
Project FeederWatch is direct about it: "concrete basins often crack if they freeze during winter." Audubon's winter guidance recommends avoiding ceramic baths on the grounds that they can crack in cold weather, and steers readers to a plastic bath with a built in heater instead.
Both are right, and the mechanism is in our guide to cleaning a concrete bird bath: concrete is porous, the walls of the casting absorb water, and it is the water inside the wall that expands and takes the surface off. Adding a heater does not solve that. A heater keeps the basin liquid. It does nothing for the water already in the material, and it gives you a false sense that the bath is now winter proof.
So the arrangement we would actually recommend, which sells you nothing extra.
- Before the first hard freeze, drain the concrete bath, let it dry through, and store it under cover or wrap and invert it
- Run a cheap plastic or resin basin with a de-icer through the freezing months
- Put the concrete one back out in spring
Our winter care guide for concrete bird baths covers the storage options in detail, and the article on whether a concrete bird bath will crack over winter covers what happens if you do not.
If you want a bath that stays out year round, that is a plastic one with a heater, not a concrete one. Our own concrete bird baths are three season objects and we would rather say so than sell you a cracked basin in March.
If you do not want to run a cord
Audubon Rockies gives three options in one line, and only the third involves electricity: keep the water thawed "by adding warm or hot water, making a hole in the ice, or using a simple birdbath heater."
- Pouring warm water
- works, and needs repeating. It buys a few hours in hard cold rather than a day.
- Breaking the ice
- also works. Lift the sheet out rather than smashing it in place, particularly on anything ceramic or concrete, where the impact is doing to the basin what you spent the autumn avoiding.
- Refilling more often than you expect
- Audubon notes that "Frequent refills are necessary in winter because the water quickly evaporates in dry air." Cold air is dry air, and an open bath loses volume even when it is not being used.
Two tricks we see constantly and cannot source: a dark colored basin absorbing enough sunlight to delay icing, and floating a ball in the water so wind driven motion keeps a hole open. Neither appears in any Cornell, Audubon, or extension material we could reach. They may well work. We just cannot tell you that anybody has checked.
Things that do not change in winter
- Depth
- no source we found gives a different winter figure. Cornell's 1 inch at the edges and 2 inches maximum in the middle is stated as general guidance and repeats in winter contexts. If depth is new to you, it is check one in our guide to why birds are not using a bird bath.
- Placement near cover
- Audubon: "Make sure there's ample water near protective shrubs." The same trade between open sightlines and escape cover applies in January.
- Cleaning
- a frozen bath still accumulates droppings and debris between thaws. The routine is in our guide to keeping bird bath water fresh.
One thing we could not answer
People ask whether a de-icer warms the water or merely stops it freezing, and whether warm water is bad for birds in cold weather. We could not find a statement on either question from any source we would cite. Thermostatically controlled is the phrase Cornell uses, which implies the unit is holding a set point rather than heating without limit, but that is us reading a word rather than a source answering the question. If you know of a published answer we would like to see it.
Frequently asked questions
How do I keep my bird bath from freezing?
A thermostatically controlled de-icer or a bath with a heater built in. Cornell notes that most new immersion models switch off if the water dries up. Without electricity, Audubon Rockies lists adding warm water or opening a hole in the ice, both of which need repeating through the day.
Can I put antifreeze or glycerin in a bird bath?
No. Cornell says to never add antifreeze and states it is poisonous to all animals including birds, and warns that glycerin "can saturate and mat a bird's feathers leaving it susceptible to hypothermia." Project FeederWatch adds that ingesting glycerin raises a bird's blood sugar and can be fatal.
Do birds need water in winter?
The sources differ in emphasis. Cornell says keeping a bath ice-free in winter "is not critical" because birds can usually get what they need from snow or dripping icicles. Audubon says many kinds of birds bathe in and drink from open water in frigid weather, and recommends a heated bath. Both are worth reading before you decide.
Can I leave a concrete bird bath out in winter with a heater?
We would not, and we sell concrete bird baths. Project FeederWatch notes that concrete basins often crack if they freeze. A heater keeps the water liquid but does nothing about water already absorbed into the porous wall of the casting, which is what actually breaks it.
How much does a bird bath heater cost to run?
Project FeederWatch says pennies a day. No bird organization or extension service publishes a wattage figure, so run the arithmetic on your own unit: watts divided by 1000, times hours per day, times days, times your electricity price. The EIA reported a US residential average of 18.44 cents per kilowatt hour in May 2026.
Is an extension cord safe for a bird bath heater?
Only an outdoor rated one on a GFCI protected outlet. NFPA states that all outdoor receptacles should be GFCI protected, and recommends extension cords listed by a qualified testing laboratory and marked for outdoor use. An indoor cord run out of a window is not that.
References
- Reference: Attract Birds With Birdbaths | The Cornell Lab of Ornithology, All About Birds
- Reference: Providing Water for Birds | Project FeederWatch, The Cornell Lab of Ornithology
- Reference: Winterize Your Yard for Birds | National Audubon Society
- Reference: How to Provide Water for Birds and Butterflies | Audubon Rockies
- Reference: Feeding Birds in Winter | University of Nebraska Lincoln Extension, Lancaster County
- Reference: Electrical Safety | National Fire Protection Association
- Reference: Extension Cords | United States Consumer Product Safety Commission
- Reference: Electricity Monthly Update, End Use | United States Energy Information Administration