Seasonal

Hummingbird Nectar Ratio in Winter: 3:1 or 4:1?

Both mixes are safe for hummingbirds in cold weather. The stronger one buys less than one degree of freezing protection, which is why the ratio is the smaller half of keeping a winter feeder open.

Use 4:1 nectar all winter, or switch to 3:1 in a cold snap if you like. Both are safe for hummingbirds. But a 3:1 mix starts to freeze less than 1°F lower than 4:1, so the ratio will not keep a feeder liquid on a freezing night. What does that is swapping feeders, bringing the feeder in overnight, or a heater.

That gap is the number this page adds. Birds Connect Seattle, the Seattle Audubon chapter, says 4:1 nectar "will begin to freeze around 29 degrees." We worked out each common mix from a published sucrose table, and the stronger mix barely moves the line.

What 4:1 and 3:1 mean#

A nectar ratio is parts of water to parts of plain white sugar. A 4:1 mix is four cups of water to one cup of sugar. A 3:1 mix is three cups of water to one cup of sugar, so it is the stronger of the two.

The same mix is often written the other way round. Birds Connect Seattle and the National Audubon Society write 1:4, sugar first. Sheri Williamson, quoted below, writes 3:1, water first. 1:4 and 4:1 are the same recipe.

How you measure matters too. Most people use cups, as our nectar calculator does. A cup of granulated sugar weighs about 200 g and a cup of water about 237 g. So a 4:1 mix made with cups is 17.4% sugar by weight. Made by weight, 4:1 is 20% sugar. A 3:1 cup mix is 22% sugar, and 3:1 by weight is 25%.

Freezing point depression is how far dissolved sugar pushes the start of freezing below 32°F (0°C). The more sugar, the bigger the drop. The University of Guelph's food science department publishes the figures for plain sugar in water, for ice cream makers. Its table gives a drop of 1.29°C at 21 g of sugar per 100 g of water, and 2.03°C at 33 g. The table notes that its values were extrapolated from Leighton (1927), who drew on Pickering (1891).

That figure is where the first ice crystals form, not where the mix turns solid. Ice forms out of the water, so the syrup left behind gets stronger and must get colder before more ice forms. Guelph's freezing-curve method works this way, and we used it to work out how much of each feeder is ice.

One cold night, worked through#

Take a feeder under an eave in the Pacific Northwest, where Anna's hummingbirds stay all winter. Suppose the forecast low is 27°F (-2.8°C), reached just before dawn. Suppose the feeder holds a 4:1 mix made with cups. Walked through the Guelph table, the night goes like this:

• At about 29.7°F (-1.3°C), the first ice crystals form.
• By 28°F, about 42% of the water is ice.
• At the 27°F low, about 53% is ice. The liquid left is a syrup of about 31% sugar.

Now run the same night with a 3:1 mix made with cups:

• The first ice forms at about 28.9°F (-1.7°C), less than a degree later.
• At the 27°F low, about 37% of the water is ice.

Both feeders are slush at first light, when a wintering hummingbird most needs to feed. The stronger mix made less ice, not an open feeder.

Change one thing: the low is 29°F instead. Now the 4:1 feeder has some ice in it, about a fifth of its water. The 3:1 feeder has none. That narrow band, from about 29 to 30°F, is the only place where the ratio decides whether the nectar stays clear.

Freezing points of common mixes#

The last three columns show how much of the water is ice at each air temperature.

Every figure comes from the Guelph table, using 200 g for a cup of sugar and 237 g for a cup of water. Compare like with like and 3:1 starts to freeze 0.8°F below 4:1 when you use cups, and 0.9°F below when you weigh. By 20°F, every mix on the list is mostly ice.

The 2:1 row shows the ceiling. Even a mix twice as strong as 4:1 only holds off ice to 27.3°F. No source we read recommends 2:1 for a feeder, and Williamson's own range stops at 3:1.

Why the advice splits#

The 4:1-all-year side. Birds Connect Seattle says to "keep the mix at 1:4 ratio sugar to water." It warns that stronger sugar "cannot travel up the grooves of their tongue easily and may also damage kidneys and liver." The National Audubon Society's feeding FAQ gives 1:4 and says nothing about changing it in winter. Project FeederWatch also gives one part sugar to four parts water.

The 3:1 side. Sheri Williamson wrote the Peterson field guide to North American hummingbirds. Her statement was shared on the Mid-Valley Nature email list. In it, she recommends three to five parts water to one part sugar, and says she now feeds 3:1 most of the year. Her reason: "a 1:3 ratio allows them to feed more efficiently, which is important when they're under stress from migration or cold weather." In the cold, she adds, the bird takes in less "cold water that has to be warmed to body temperature."

Don Powers, a hummingbird physiologist at George Fox University, agreed on the Oregon birding list in December 2021. He wrote that he agreed "with Sheri's assessment" and that 3:1 "will depress the freezing point of the solution a bit." A bit is the right word. It is under 1°F.

So each side is right about one thing. The 3:1 side has the better case on safety. The 4:1 side is right that switching does almost nothing against freezing.

Is 3:1 nectar safe for hummingbirds?#

Yes, on everything we could find.

Is it stronger than flowers? No. W. Mark Roberts, writing in The Auk in 1995, gives the average for North American and many tropical hummingbird flowers as 20 to 25% sugar by weight. A 4:1 mix made with cups (17.4%) sits below that range. A 3:1 mix made with cups (22%) sits inside it. Williamson puts the flower average "close to 3:1."

Is it too thick to drink? Stronger nectar is thicker, so each lick takes up less. Roberts measured this in a rufous hummingbird: licks per second and the amount per lick both fell as sugar went up. But the bird's energy intake was "significantly higher at 25 to 35% sucrose than at higher concentrations." A 2011 model by Kim, Gilet and Bush put the best sugar level for the way hummingbirds drink at 33%. A 3:1 mix, at 22 to 25% sugar, is no stronger than the low end of Roberts's range and is below the model's best level.

Does it harm kidneys or liver? Birds Connect Seattle names no study for that, and we found none. On dehydration, Powers wrote that hummingbirds "turn over 2-5X their body weight in water each and every day." So, he said, "it is highly unlikely that a 25% rather than a 20% sucrose solution is going to dehydrate tissues." He added that he knew of no work that suggested it.

The one real limit is heat. Williamson's statement says mixes stronger than 3:1 "may not provide sufficient water in extremely hot, dry conditions." She feeds 3:1 most of the year except on "the very hot, dry days of late spring and early summer," and says a 5:1 mix can help birds "through extreme heat and drought." That is why our page on the desert Costa's hummingbird keeps to the standard mix. Hot nectar also spoils fast, so go back to the hot-weather change schedule in the nectar recipe.

Cold nectar is not a risk in itself. The Audubon FAQ says it "does not appear to 'cold stun' the birds and is not a concern."

What actually keeps nectar liquid#

If nights drop below about 29°F, the ratio does not decide it. These do, and the details are in keeping nectar liquid in the cold.

• Swap two feeders. Keep one indoors and trade them at dawn and dusk. Birds Connect Seattle says rotating feeders "will keep the fluid moving and available to the birds."
• Bring it in overnight. Hummingbirds do not feed in the dark. Put it back out before first light.
• Use a feeder heater. Pick one built for the job and rated for outdoor use, on a GFCI-protected outlet. The same wiring rules are on winter water and heated bird baths.
• Hang it somewhere warmer. Under an eave, close to the house.

None of these needs a stronger mix. Nothing else belongs in the bottle either: no salt, no glycerin, no alcohol. The nectar recipe explains why. Winter nectar still needs changing and the feeder a wash; see cleaning a hummingbird feeder.

A heater that stops in a power cut leaves you with the swap; see feeding birds through storms and outages.

Which ratio to use#

If you want one rule: pick the ratio for the sugar, not the freezing point. A 3:1 cup mix has about a quarter more sugar in each sip than a 4:1 cup mix, which is the reason Williamson gives for it. The rest of the cold-weather yard is in winter bird feeding and feeding birds in extreme cold.

Where this page stops applying#

The freezing figures are for clean sugar water sitting still, taken from a table its authors extrapolated. Read them as where ice starts in a clean mix, not as a promise for a used feeder. A forecast low is also not a reading at your feeder, which can sit colder or warmer than the weather station.

The safety case for 3:1 rests on flower nectar ranges, two intake studies and the views of two specialists. Nobody we read has tracked feeder birds on 3:1 against 4:1 through a winter. This page also does not cover other sweeteners, oriole feeders or a hummingbird in trouble. A grounded or injured bird needs a licensed wildlife rehabilitator, not a stronger mix.