Homemade suet: rendering the fat and three mixes that actually hold

The short answer

• Render twice. The first render melts the fat out, the second drives off the water left behind, and it is the water that makes a cake go moldy and rancid.
• Buy about 1.5 lb of raw beef fat for every 1 lb of tallow you want. Kidney suet gives the hardest result, with a melting point around 113 to 118 °F.
• Firmness is set by two things: how much dry matter you carry in the fat, and whether you added peanut butter. Peanut butter oil is liquid at yard temperature and is the single biggest softener.
• Bacon grease, roasting-pan drippings, salted fat and used cooking oil are not suet substitutes. Salt, cure and liquid oils all cause real harm.
• Plain twice-rendered tallow keeps about a year at 0 °F. A mixed cake with seed and nuts in it keeps 6 to 9 months, because the seed oils go before the fat does.

Suet in the bird feeding sense means hard beef fat that has been rendered: melted down, cleaned of tissue and water, and set solid again. The hardest and cleanest fat on a cow is the crumbly white kidney fat, and a butcher will usually sell it cheaply or hand it over. Trim fat off a joint works too, but it renders softer and sets softer.

The reason to make your own is not price. It is control: you decide the fat fraction, so you decide the temperature the cake survives. What you get is a near-white, almost odorless block that sets hard, does not weep in a March thaw, and keeps for months in a freezer.

• Top-tier favorite for: Black-capped Chickadee, Tufted Titmouse, White-breasted Nuthatch, Red-breasted Nuthatch, Downy Woodpecker, Hairy Woodpecker, Red-bellied Woodpecker, Northern Flicker, Carolina Wren, European Starling
• Eaten readily by: Blue Jay, Eastern Bluebird, Steller's Jay, California Scrub-Jay, Common Grackle
• Taken occasionally by: Northern Cardinal, American Robin, Baltimore Oriole, House Sparrow, Red-winged Blackbird

That is the audience. Note the last name on the list: starlings rate suet as highly as woodpeckers do, so if a cake vanishes inside a day the recipe is not the problem. Move to a recessed or upside-down design as described under suet feeders, and see starlings at feeders for the rest of it.

Why the second render is the whole trick#

Raw fat is water, connective tissue and traces of blood and meat juice as well as fat. One render melts the fat away from the tissue, and most people stop there. A single render still leaves fine droplets of water and dissolved protein suspended in the fat, and those are exactly what mold and bacteria need. A cake made from once-rendered fat grows gray fuzz in a mild wet week and smells like old crayons within a couple of months.

The second render fixes it in two moves: a water chill that lets the impurities settle out underneath the fat, then a dry re-melt that boils off the last of the moisture.

First render#

Chill the raw fat hard and cut it into pieces no larger than 1/2 in. Cold fat dices cleanly; warm fat smears and you end up with lumps that never render through. Put it in a heavy pan on low, or a slow cooker on low, and bring it to 200 to 250 °F. Do not chase speed. Above about 275 °F the fat browns, picks up a meaty smell, and starts down the road to rancidity before you have even molded it.

It will bubble steadily. That is the water boiling off at 212 °F, not the fat frying. The render is finished when the bubbling stops, the pan goes quiet, and the cracklings sink and turn golden. Allow 2 to 3 hours on a stovetop for 3 lb of diced fat, 4 to 5 hours in a slow cooker.

Strain while it is hot#

Beef tallow starts to set at roughly 113 to 118 °F, so strain it well above that, at 140 °F or more, or it will seize in the filter. Two passes: a fine sieve to take out the cracklings, then muslin, a clean cotton cloth or a paper coffee filter to take out the fine sediment. A coffee filter is slow and worth it.

Chill, scrape, then render again#

Pour the strained fat into a bowl over about a cup of cold water and refrigerate overnight. The fat sets as a disc floating on the water, and everything that was not fat collects on the underside as a soft brown layer. Lift the disc out, scrape that layer off with a spoon, and throw it away with the water.

Now melt that disc on its own with no water, hold it at 225 to 250 °F for 20 to 30 minutes, and watch it go from cloudy to clear. When it stops crackling entirely it is dry. Strain once more through a coffee filter and let it set. The result should be pale, firm, and smell of almost nothing. That is your working tallow.

Yield: figure on about 1 lb of finished tallow from 1.5 lb of raw kidney suet. Trim fat runs a little lower and softer.

Three mixes, chosen by the temperature they have to survive#

The dry ingredients are not filler. They give clinging birds something to grip, they carry the seed, and above all they raise the temperature at which the block holds its shape. The other lever is peanut butter: its oil is liquid at 60 °F, so every gram of it drags the whole cake softer. Cold-weather mixes can afford it. Warm-weather mixes cannot.

Mix A: deep winter, below 40 °F#

• 454 g (1 lb) tallow, melted, about 2 cups
• 225 g unsalted peanut butter, about 1 cup
• 340 g yellow cornmeal, about 2 2/3 cups
• 115 g rolled oats, about 1 1/4 cups
• 115 g sunflower hearts or chopped unsalted peanuts, about 3/4 cup

Roughly 1,250 g of dough: four standard cakes, or about twenty 60 g muffin-cup balls. This is the highest-energy mix here and the softest, built for January nights. Above 45 °F it goes greasy on the wire.

Mix B: shoulder season, 40 to 65 °F#

• 454 g tallow, melted
• 400 g yellow cornmeal, about 3 cups
• 170 g plain flour, about 1 1/3 cups
• 60 g sunflower hearts, a scant 1/2 cup

Roughly 1,080 g, or three and a half cakes. No peanut butter, more dry matter, and it holds a square edge through a mild spring afternoon. Use it from late March through April in most of the country, and through much of the winter in the Deep South and coastal California.

Mix C: warm and crumbly, 65 to 80 °F#

• 454 g tallow, melted
• 570 g yellow cornmeal, about 4 1/3 cups
• 115 g plain flour, about 1 cup
• 60 g dried mealworms, about 1 1/2 cups

Roughly 1,200 g, enough for about thirty plug holes of 1 in by 3 in. At this ratio the dough will not hang together well as a slab in a cage, but it packs beautifully into drilled log holes, where the wood shades it and holds it. The mealworms bring in wrens and bluebirds that ignore a plain fat cake.

What never goes in#

• Bacon grease. Cured, salted and smoked. The salt load is the problem and it is not a small one for a 12 g bird, and the fat stays soft enough to coat plumage.
• Roasting-pan drippings and gravy fat. Salted, seasoned, and full of meat juices and water that spoil quickly. If it was seasoned for you, it is not for them.
• Leftover cooking oil, vegetable oil, olive oil. Liquid at every temperature your yard will ever see. It soaks into feathers and wrecks their waterproofing, and it oxidises fast.
• Anything salted or sweetened. Salted peanut butter, salted nuts, cake and pastry scraps. See what not to feed birds for the full list and the reasoning behind each one.
• Fat you did not render. Once you are making cakes to store, unrendered fat is the single most common reason a batch goes bad in the freezer bag.

Molding: cakes, plugs and balls#

Let the mixed dough cool to 100 to 110 °F and stir it as it thickens. You are waiting for the texture of stiff cake batter, thick enough that a spoonful holds a peak. If you pour while it is still hot and thin, the cornmeal and seed sink, and you get a cake with a hard clear fat cap on top and a dry crumb underneath that falls out of the cage in one lump.

• Cakes. Line a shallow 8 in square tin with parchment, press the dough in to 1.25 in deep, level the top with the back of a spoon, chill 2 hours and cut into four. That is four squares of about 4 in, close enough to the standard 4.5 in cake footprint that a wire cage takes it. An empty tray saved from a shop-bought cake is an even easier mold.
• Plugs. Pack stiff dough into the 1 in holes of a log feeder with the end of a wooden spoon, working it down to fill the base of the hole rather than bridging it. Alternatively, press dough into a length of 1 in pipe, freeze, and push out solid cylinders with a dowel. Plugs and cakes suit different birds and different pests, worked through in suet cakes versus suet plugs.
• Balls. A muffin tin with paper cases gives 60 g portions that fit a small hanging cage and let you test a new mix without committing a whole batch.

Never hang fat in a plastic mesh onion bag or netting. Birds catch toes and tongues in it.

Storage life, honestly#

These are our working figures rather than lab results, and they assume a cake that was cooled and wrapped properly in the first place.

The mixed cakes go first because the sunflower and peanut oils in them oxidise faster than beef fat does, which is the same reason sunflower hearts have a shorter shelf life than seed still in the hull. Wrap each cake in parchment, bag it, and write the mix letter and the date on the bag. Everything you need for the rest of the pantry is in storing birdseed.

Reading a cake that failed#

Scrub the cage itself when you change cakes. Fat films on wire, collects seed dust and holds bacteria, and hot soapy water takes it off in a minute; the full routine is in how to clean a bird feeder. If you would rather buy than render, the trade-offs are laid out in suet for birds.

Frequently asked questions#

Do I really have to render suet, or can I just hang the raw fat?

In hard frost you can hang raw fat and it will be eaten. Above about 40 °F it fails. Raw suet holds water, blood and connective tissue, and all three spoil: it goes slimy, grows mold, and turns rancid within days. Rendering melts the fat away from the tissue and boils off the water, which is why rendered tallow keeps for months and raw fat keeps for a few cold days. If you are only feeding in a January cold snap, raw is workable. For anything else, render.

Why does my homemade suet melt when the shop-bought cakes do not?

Most commercial no-melt cakes are built on a blend that is stiffened with a lot of flour, cornmeal and sometimes hydrogenated fat. Two things make a homemade cake soft: peanut butter, whose oil is liquid at 60 °F, and too little dry matter. Drop the peanut butter and carry more cornmeal and flour per pound of fat and the same tallow will hold shape 20 °F higher. Nothing homemade survives an 85 °F afternoon in the sun, so take it down instead.

Can I use bacon grease in suet for birds?

No. Bacon is cured and salted, and the drippings concentrate both. Small birds have little tolerance for a sodium load that size, and the nitrite cure and smoke residues add nothing good. Bacon fat also stays soft at room temperature, so it coats feathers rather than being chipped off in flakes. The same applies to roasting-pan drippings, gravy fat and any fat that has been seasoned. Use plain raw beef suet from a butcher, which is usually cheap or free.

What is the best mold for suet cakes?

Keep one empty plastic tray from a shop-bought cake and reuse it, or line a shallow 8 in square tin with parchment, fill it to 1.25 in deep and cut four squares. Both give you the standard cake footprint of roughly 4.5 in square, which is what a wire suet cage is built around. For a log feeder, pack stiff dough into the 1 in holes with the end of a wooden spoon, or freeze the dough inside a length of 1 in pipe and push out cylinders.

How long does homemade suet keep in the freezer?

Plain twice-rendered tallow with nothing in it keeps about a year at 0 °F and is still good after that, just duller in flavor, which birds do not care about. Cakes with sunflower hearts, peanuts or oats in them keep 6 to 9 months, because those oils oxidise faster than the tallow. In the fridge, allow 4 to 6 weeks. At room temperature in a cupboard, 1 to 2 weeks. Label every bag with the date, because rancid fat is hard to judge once it is cold.

Is peanut butter safe for birds?

Plain unsalted peanut butter with no added sweetener is fine, and chickadees, titmice, nuthatches and woodpeckers take it readily. Avoid salted or reduced-fat versions, and avoid anything containing sugar substitutes. Do not smear it on thickly in warm weather: bound into a fat and cornmeal mix it is safe, but a thick soft layer on its own is messy on feathers. Treat it as a cold-weather ingredient and leave it out of any mix you will hang above 40 °F.

Sources and further reading

1. Feeding Birds Cornell Lab of Ornithology, Project FeederWatch Which species use suet, how it is offered, and hygiene practice for feeders holding fat
2. Bird Feeding and Care National Audubon Society General guidance on suitable and unsuitable foods