Bird Food

Black Oil Sunflower Seed

One seed feeds more North American backyard birds than every mix on the shelf combined. Here is what it is, who eats it, and where it still falls short.

Black oil sunflower is the small seed with the thin black shell, and it feeds more North American backyard species than anything else you can buy. Chickadees, finches, nuthatches, titmice, cardinals, jays, grosbeaks and several woodpeckers all take it readily. If you own one bag of bird food, this is the bag.

The reason is not the fat, although the fat helps. It is the shell. A black oil hull is thin enough for a bird weighing half an ounce (14 g) to split with a few bites, which is not true of the striped sunflower sitting next to it on the shelf. Shell thickness, not flavor, decides most of what happens at a feeder.

This page covers what the seed actually is, which birds take it and which ignore it, how it behaves in each feeder type, what it really costs once you subtract the hull, and the mistakes that turn a good bag into a wasted one.

What black oil sunflower actually is#

It is the seed of Helianthus annuus, the same plant grown for cooking oil, harvested from oilseed cultivars rather than the larger confection types sold for human snacking. The seeds are small, almost uniformly black, and roughly 3/8 inch (10 mm) long.

Oilseed sunflower kernels are usually given as around 40 percent fat, against roughly 25 to 30 percent for confection strains. That is a meaningful gap for a bird trying to replace overnight weight loss in February, and it is why black oil turns up on every list of high-energy cold weather foods.

The kernel also carries useful protein and is soft enough that even a fledgling can handle a piece of it. There is no processing involved: what you buy is raw whole seed, unroasted and unsalted, which is the only form that belongs in a feeder.

The shell is the real reason it wins#

Feeder ecology comes down to which birds can open what. A hull that takes a chickadee twenty seconds to work through is a hull that gets opened. A hull that takes ninety seconds is a hull that gets abandoned in favor of the next feeder down the street.

Black oil sits at the easy end of that range for almost every seed-eating songbird in the lower 48. A black-capped chickadee carries one seed to a branch, wedges it under its toes and hammers it open in a few seconds. A goldfinch works it in the bill without leaving the perch. A cardinal shears it with a single scissoring motion.

Which birds take it and which ignore it#

Almost all of the species people set feeders up for will eat black oil sunflower. The exceptions are worth knowing, because they explain why a yard full of sunflower can still feel like it is missing something.

If your feeders are all sunflower and you never see a bluebird or an oriole, the seed is not the problem, the menu is. The full breakdown of who eats what lives in the bird food chart.

How it behaves in each feeder#

Black oil is the only common seed that works acceptably in every mainstream feeder design, which is a large part of its dominance.

Tube feeders. Near-perfect. The seed is small and uniform, so it flows past a 3/8 inch (10 mm) port without bridging. This is the pairing most tube feeders are designed around.

Hopper feeders. Excellent, with one caveat: hoppers hold a lot, and a slow yard will keep the bottom third sitting for weeks. Fill to half in a quiet season.

Platform and tray feeders. Excellent for the birds, messy for you. An open tray lets cardinals and jays feed comfortably but also lets rain in, so use a platform feeder with a mesh floor rather than a solid one.

Window feeders. Fine, and the shells make it obvious when a feeder is being used. Expect to sweep a sill.

Ground. Works, but only in quantities that clear within a day.

What it costs per usable calorie#

Whole black oil sunflower is roughly a quarter shell by weight. The exact fraction varies by crop and grade, but a quarter is a fair working number, so a 20 pound (9 kg) bag delivers somewhere near 15 pounds (6.8 kg) of kernel to the birds and about 5 pounds (2.3 kg) of hull to your lawn.

That still leaves it as the cheapest reliable calorie at a feeder. Sunflower hearts contain no waste at all but typically sell for around twice the price per pound, which makes the two close to even on kernel delivered, with hearts slightly behind once you account for faster spoilage. Cheap mixes look cheaper per pound and are not, because a large share of the bag is milo and wheat that gets raked onto the ground untouched.

The honest ranking, cost per calorie a bird actually eats: black oil sunflower first, hearts a close second, striped sunflower and safflower behind them, supermarket mixes a distant last.

The mess underneath, and what to do about it#

Every pound of black oil sunflower produces a few ounces of hull that lands under the feeder. Sunflower hulls also release compounds that suppress plant growth, so a feeder left in one spot over a lawn will leave a bare ring by the second season.

Three fixes, in order of effort: hang a catch tray under the feeder and empty it weekly, move the feeder 10 feet (3 m) every few months so no patch takes the whole load, or put a slab of gravel or mulch under it and rake it out twice a year. The full set of tactics is in seed mess, hulls and dead grass.

Do not let hulls pile up damp. That mat is where feeder-borne disease and rodent problems start.

Buying and storing without losing half the bag#

Sunflower does not rot in an obvious way. It goes rancid, which smells like old cooking oil and paint rather than anything mold-like, and birds detect it long before you do. A full feeder that nobody is touching is very often a rancid feeder.

• Buy about a month of seed at a time, even when the larger bag is cheaper per pound.
• Store it in a sealed metal or thick plastic bin, somewhere cool and dark. Heat is what drives the fat rancid.
• Never pour fresh seed on top of old. Empty, wipe out and dry the container first.
• In humid summers, freezing a portion for a few days after purchase kills moth and beetle larvae that came in with the bag.

Full method, including what to do about an infestation you have already got, is in storing bird seed.

Four mistakes worth avoiding#

1. Treating the price per pound as the price of the food. Compare bags on kernel delivered. A mix that is 30 percent milo is not cheap seed, it is expensive sunflower with ballast.
2. Buying a 40 pound (18 kg) bag for a quiet yard. The last third will be rancid before the birds reach it, and you will have spent more per usable pound than someone buying small bags fresh.
3. Expecting it to solve a squirrel problem. Squirrels like black oil sunflower as much as the birds do. Only geometry and baffles fix that, as covered in how to stop squirrels raiding feeders.
4. Topping up instead of emptying. The seed at the bottom of a feeder never gets eaten first. Empty and dry the feeder at each refill and the rancid layer never forms.

Get those four right and black oil sunflower is close to a solved problem: one seed, in one or two feeders, feeding the large majority of what your yard has to offer.