Mealworms for birds: live, dried, and how much is too much

The short answer

• Dried mealworms run about 50% protein and 28% fat, roughly 500 kcal per 100 g, which is why a tablespoon or two is a meal and a full dish is a problem.
• Rehydrate dried mealworms in warm water for 15 to 30 minutes during nesting season. Nestlings get nearly all their water from the food an adult carries in.
• Live worms keep for four to six weeks in a ventilated container in the fridge at 40 to 50 °F with bran bedding and a carrot slice for moisture.
• Mealworms are low in calcium and high in phosphorus, so keep them a supplement rather than a staple, and put out crushed baked eggshell alongside them in spring.
• Put out what disappears in 15 minutes. If worms are still sitting there after an hour, you have fed the ants and the starlings, not the bluebirds.

Mealworms are darkling beetle larvae, sold live in tubs of bran or dried in bags, and they are the only common feeder food that a bird raising young will treat as first-choice rather than convenient. Everything else you put out is seed or fat: useful for an adult, mostly wrong for a nestling. That is the whole case for keeping a small tub of worms around, and it is also why the food needs more care than a scoop of sunflower.

Live or dried: the difference is behavior, not nutrition#

Drying a mealworm removes water. It does not remove the protein or the fat, so a dried worm and a live worm of the same original size deliver roughly the same nutrients once you allow for the moisture. Dried worms are about 50% protein and 28% fat by weight, which puts them well above every seed on this site and above suet on protein.

What changes is whether a bird notices them.

The practical route for a new dish is live first, dried after. Run live worms for two or three weeks until a pair has learned that the dish means food, then switch to dried and keep a handful of live ones for cold snaps and for the week the young fledge. If you want the full head to head, see live versus dried mealworms.

The calcium problem, and the eggshell fix#

Mealworms are lopsided food. They carry a lot of phosphorus and very little calcium, and a growing bird building bone needs calcium in the other direction. In captive insectivores this imbalance is managed by dusting insects with a calcium supplement before feeding. For wild birds at a dish, the honest answer is simpler and more reliable: keep mealworms a supplement, not a diet.

You can put the calcium back directly. Rinse eggshells, bake them at 250 °F for about 20 minutes to dry them and kill off surface bacteria, crush them to pieces smaller than a quarter inch, and put them out on a flat tray near the worm dish in April and May. Females forming eggs take calcium readily, and it costs nothing. This pairs naturally with feeding during nesting season, where the wider question of what helps and what does not is worked through.

Rehydrating dried worms, and the six weeks it matters most#

A nestling does not drink. Every drop of water it gets arrives inside the food its parents carry in, which in a normal year is caterpillars, spiders and soft insects that are mostly water. A dry mealworm is the opposite of that: concentrated protein with the water taken out.

So from the first hatch through fledging, soak them.

1. Put the worms in a mug and cover them with warm tap water. Not boiling.
2. Leave them 15 to 30 minutes. They swell, darken slightly and go from snapping to bending.
3. Drain them properly. Standing water in the dish sours fast and turns the leftovers to paste.
4. Put out only what will be eaten in one session, and tip out the remainder at the end of the day.

Soaked worms roughly double in weight, so one tablespoon dry becomes about two tablespoons wet. Adjust your portion by volume after soaking, not before, or you will double the serving without meaning to.

Keeping live worms alive#

Live mealworms are dormant, not dead, and cold is what keeps them that way. In the fridge at 40 to 50 °F they stop eating, stop pupating and last four to six weeks. At room temperature they will run through their life cycle in a few weeks and you will end up with beetles.

• Container. A smooth-sided tub with a ventilated lid, or the tub they arrived in with pin holes punched in the top. They need air, not humidity.
• Bedding. An inch or two of wheat bran or rolled oats. This is bedding and food at once.
• Moisture. A slice of carrot or potato laid on the surface. Replace it every few days before it goes furry. Never add free water: damp bran grows mold and the colony dies.
• Weekly service. Take the tub out for a few hours once a week so they warm up and eat, pick out any dark or dead worms, then return it to the fridge.
• Fridge placement. The door shelf is usually the warmest part of a fridge and the right place for them. The back of the bottom shelf can freeze them.

Sift out the fine dust and shed skins when you top up the bran. That dust is the main thing that makes a mealworm tub smell, and there is no reason to tolerate it.

Portioning: a handful, not a bowl#

This is where most people go wrong, and it costs them money as well as birds. Dried mealworms are the most expensive food on this site by a wide margin, roughly seven times the price per pound of black oil sunflower, and they are also the food most likely to be tipped in by the scoop.

Some working arithmetic, using a working figure of about 4 g per level tablespoon of dried worms:

• 1 level tbsp is about 4 g, or roughly 20 kcal.
• A pound of dried worms is about 113 tablespoons, so about 56 two-tablespoon servings.
• At roughly $9.50 per pound, a two-tablespoon serving costs about 17 cents.
• Two servings a day for the whole nesting season is under a pound and a half of worms.

That is a manageable bill. Filling a 2 cup dish and topping it up is not: the same pound is gone in a week, and most of it went into starlings.

Timing helps as much as volume. Two short sessions, one at first light and one in late afternoon, teach the pair a schedule and give the starling flock less to find.

Which birds actually take them#

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

Two things in that list are worth saying out loud. First, the birds most people buy mealworms for, Eastern Bluebirds and Carolina Wrens, sit right at the top, along with chickadees, titmice and American Robins. Second, so do European Starlings and Common Grackles. There is no seed choice that separates those groups, because they all want the same thing. The separation has to be mechanical: a cage, a dome or a small entry hole, which is what mealworm feeders are built around.

Woodpeckers, nuthatches and jays will all take worms opportunistically. They are not the reason to buy them, but they explain why a dish left out empties faster than the bluebirds can account for.

Where the dish goes#

Mealworm dishes work best low and open: on a post, a railing or a pole about 4 to 5 ft up, with a clear sightline and a perch tree within 20 or 30 ft. Bluebirds hunt from a perch and drop onto food, so they want to see the dish from somewhere before they commit.

Keep it away from your seed feeders. A worm dish under a busy sunflower tube gets rained on with hulls, and the hulls go into the worms. Cleaning is easy and non-negotiable: tip out leftovers daily, and wash the dish with hot soapy water at least weekly using the routine in how to clean a bird feeder. A dish that holds damp protein in summer heat is exactly the surface where feeder-borne disease spreads, which is covered in bird diseases at feeders.

If nothing comes for the first fortnight, the problem is usually visibility rather than the food. Move the dish somewhere with a bare perch above it, use live worms until you get a first visit, and read no birds at my feeder before changing anything else.

Frequently asked questions#

Are dried mealworms as good as live ones?

Nutritionally they are close: drying removes water, not protein or fat. Behaviorally they are not the same. Live worms move, and movement is what makes a bluebird or a wren notice a dish in the first place. Most yards get the best of both by starting with live worms for two or three weeks until birds have learned the dish, then switching to dried for everyday feeding. In nesting season, soak dried worms before putting them out so they carry water as well as protein.

How do you rehydrate dried mealworms?

Cover them with warm (not boiling) water in a mug, leave them 15 to 30 minutes, then drain and tip them into the dish. They roughly double in weight and go from brittle to pliable. Do this from the first nest of the season through fledging. Do not soak more than you will put out in one go: rehydrated worms sour within a day in warm weather, and mush at the bottom of a dish is a mold problem waiting to happen.

How many mealworms should I put out?

For a single bluebird pair, our working limit is around 100 to 150 live worms a day, split between a morning and a late-afternoon offering. In dried terms that is one to two level tablespoons per serving. The practical test beats any number: put out a small amount, and if it is gone in 15 minutes you can offer that much again. If it is still there after an hour, you have put out too much and the leftovers will draw ants, wasps and starlings.

Will mealworms attract starlings?

Yes, and grackles too. Both rate mealworms as a top-tier food, and a starling flock can strip an open dish in under a minute. The fix is geometry, not timing: use a dish inside a wire cage with 1.5 in mesh, or a feeder with a small entry hole, so bluebirds, wrens and chickadees can get in and starlings cannot. Offering worms in short timed sessions rather than leaving a full dish out all day also helps, because starlings learn a permanent food source faster than bluebirds do.

Do mealworms need a special feeder?

Any shallow dish with sides high enough to stop worms crawling out works, which for live worms means smooth vertical sides at least 1.5 in deep. Glass, ceramic and smooth plastic all defeat a mealworm; unfinished wood does not. What matters more is what goes over the dish: a dome, a cage or a small entry hole to keep larger birds off. Dried worms are lighter and blow out of an open dish in wind, so a deeper cup or a lidded feeder is worth having.

Can I feed mealworms all year?

Yes, and winter is an underrated time for it. Carolina Wrens and bluebirds that stay north in cold weather struggle exactly when insects are unavailable, and a dish of dried worms on a hard morning is genuine help. Keep servings small, put them out at first light when overnight fat reserves are lowest, and pair them with suet. In summer the case is weaker: insects are everywhere, and the main reason to feed then is the nesting pair you can watch from the kitchen.

Sources and further reading

1. Feeding Birds Cornell Lab of Ornithology, Project FeederWatch Mealworms as a feeder food, the species that take them, and the cleaning routine for dishes and open feeders
2. Attracting Bluebirds North American Bluebird Society Bluebird feeding and nest box management practice
3. Attract Birds With Native Plants and Insects National Audubon Society Role of insect food for nestlings