Mealworm feeders: dish design, portions and keeping starlings out

The short answer

• A mealworm feeder is a shallow smooth-sided dish, nothing more. The dish stops worms crawling out; everything else is about who reaches it.
• Mealworms are a supplement, not a diet. Measure a portion out, put it down, and let it run out rather than keeping the dish topped up.
• Live worms move, and movement is what a bluebird sees from 60 ft away. Dried worms work only after birds already know the dish, and they need soaking in warm water.
• A caged dish with 1.5 in mesh admits bluebirds, wrens and chickadees at 11 to 30 g and locks out starlings, grackles, jays and robins at 77 g and up.
• In nesting season a dish is most useful in a cold wet spell, when insects stop flying and a brood can starve within days.

A mealworm feeder is a shallow dish with sides a worm cannot climb. That is the entire mechanism. Everything else people argue about, the roof, the cage, the mounting, is about controlling who gets to the dish, not about holding the food.

That simplicity is why the design questions are easy and the judgement questions are hard. You can build a working dish out of a smooth ceramic ramekin in ten seconds. Deciding how many worms go in it, and when to stop, is the part that changes whether you are helping birds or just running an expensive queue.

Who actually comes to a dish#

Mealworms are one of the few foods that pull in birds that ignore seed entirely.

• 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 stand out in that list. The first is that the birds most people buy a mealworm feeder for, eastern bluebirds and Carolina wrens, rate mealworms at the top of their food list, and so do starlings and grackles. There is no food you can substitute to split them. The separation has to be physical.

The second is that chickadees and titmice take mealworms just as readily as bluebirds do. In most yards they find the dish first, because they already patrol the tube feeder six feet away and they investigate everything.

The two dish designs#

Open shallow dish. A smooth-sided tray 1 to 2 in deep, glass, glazed ceramic or slick plastic, on a post, a rail or a hanging bracket. Sides under 1 in let live worms crawl out within a minute or two. Sides over about 3 in make the dish a hole that small birds will not drop into. A 1.5 in wall with a smooth vertical inner face is the working range. Any texture on that inner face, including the grain in unsealed wood, gives a mealworm enough grip to escape.

Caged bluebird feeder. The same dish inside a wire cage, or inside a box with 1.5 in entry holes at each end. The cage is the only reliable way to keep a dish for the birds you intended. The critical dimension is not the mesh alone, it is the standoff: the cage must be at least 5 in clear of the dish on every side, or a starling stands on the outside and reaches straight through the wire. Most disappointing caged feeders fail on standoff, not mesh size.

A box-style bluebird feeder with end holes is quieter than a cage and works on the same principle, but it needs a clear line of sight through it. Birds will not enter a dark box with one entrance. Two facing holes, or one hole and a clear side panel, turns it from a trap into a tunnel.

Live or dried, and what actually changes#

The honest summary: live worms are for teaching and for stress periods, dried worms are for routine. Once a bluebird pair knows the dish, they will take dried worms without hesitating, and the season's cost drops substantially.

Soak dried worms in warm water for 10 to 15 minutes and drain them before they go out. Two reasons. Nestlings get nearly all their water from what the parents bring, and a bone-dry worm delivers none. Soaked worms are also soft enough for a fledgling to swallow whole, which a brittle one is not.

Portion control, with numbers#

Work in birds, not in scoops.

Our working figure is 15 mealworms per adult bird per day. A resident pair is 30. In practice that is a level teaspoon or so of live medium worms, roughly 10 to 13 g for 100 worms, because a medium live mealworm runs around 0.1 g. Dried worms are about a third of that weight for the same count, so 100 dried worms is closer to 3 to 4 g and a scoop that looks generous is far more worms than you think.

A practical routine that holds the line:

1. Measure the day's portion into a small container indoors. Do not carry the tub to the dish.
2. Put it out at a fixed time. First light works best: it beats the starling flock and it is when insect-eating birds are hungriest.
3. Let the dish go empty and leave it empty.
4. Add a second identical portion at mid-afternoon only if you are in a cold snap or feeding a brood.

The failure mode is topping up. A dish that is never empty is a dish that a starling flock, a jay or a squirrel will eventually monopolise, because the reward for checking it is always positive. An empty dish teaches every opportunist that the site is not worth a detour, while the pair that nests 40 ft away still learns the schedule.

Training a bluebird to the dish#

Bluebirds do not recognize a dish as food. They recognize movement in an open place they can see from a perch. The sequence that works, over about two weeks:

1. Days 1 to 3. Put the dish in the open within 20 to 30 ft of a nest box or a favorite perch, on a post at roughly chest height. Use live worms only, 10 to 15, uncovered, no cage. Stand well back.
2. Days 4 to 7. Same time every morning. Add a visual cue you can keep forever: tapping the dish rim, or a light-colored dish that stands out against grass. The cue matters more than the food at this stage.
3. When the pair feeds twice on consecutive days, add the cage and leave everything else identical. Do not move the dish and change the food in the same week.
4. After a week on the caged dish, start mixing dried worms in at about one quarter, and increase over ten days.

If the pair has not found it in two weeks, move the dish rather than adding more worms. Bluebirds hunt from perches over short grass, so a dish in a border, under a canopy, or behind a shrub is invisible to them no matter what is in it. Placement rules for open-country birds are covered in where to put a bird feeder.

Nesting season, and when a dish genuinely matters#

The case for mealworms is strongest in a cold, wet spring spell. Flying insects stop moving below roughly 50 °F, and a bluebird brood is fed almost entirely on insects. Three gray days in a row is the situation where a measured dish does real good, and it is worth putting out a double portion of live worms during one.

Outside that, keep it modest. Chopped fruit in the same dish will bring in orioles and robins in early summer, which is a better use of the site than more worms. See feeding during nesting season for what else changes between April and July, and mealworms as a food for storage, sizing and cost per feeding.

Wash the dish more often than you think. It holds moist protein in warm weather, it is small, and it goes sour fast. A rinse each day it is used and a proper wash weekly, using the routine in how to clean a bird feeder, is the standard. Any dish left with wet residue for two days in July should be scrubbed before it is used again.

Frequently asked questions#

How many mealworms should I put out for bluebirds?

Our working figure is about 15 worms per adult bird per day, offered once or twice at fixed times rather than left out all day. A resident pair takes roughly 30, and a pair feeding nestlings will clear 100 in a morning if you let them. Measure the portion into the dish, then walk away. The dish going empty is the point: it keeps the birds hunting insects for the rest of the day and it stops the cost running away from you.

Are dried mealworms as good as live ones?

For nutrition they are close, since drying mostly removes water. For attraction they are not: a bluebird locates prey by movement, and a dried worm does not move. Dried worms work well once birds already recognize the dish as a food source. Soak them in warm water for 10 to 15 minutes and drain before serving, particularly in summer and during nesting, because a dry worm carries almost no water and nestlings get most of their fluid from food.

How do I stop starlings eating all the mealworms?

Use a cage with 1.5 in mesh set at least 5 in clear of the dish on every side. A starling weighs about 82 g and a grackle about 115 g, and neither can get through that mesh or reach through it. Bluebirds at 30 g, wrens at 20 g and chickadees at 11 g pass without hesitating. Fixed feeding times help too: put the portion out at first light, before the starling flock has finished its morning circuit.

Will mealworms attract mice or rats?

Live worms will not go far, because they cannot climb a smooth-sided dish and cannot survive long outside it. Dried worms are a different matter: they scatter, they keep, and they are a concentrated protein source. Never leave dried worms on the ground overnight, and clear spillage under the dish before dusk. If you already have a rodent problem, feed live worms only, in measured portions, and take the dish in at the end of the day.

Can I put mealworms in a regular feeder?

You can put them in a platform tray, and robins, jays and starlings will find them within minutes. That is usually the problem rather than the solution. A dedicated dish is smaller, easier to bring in, easier to wash and much easier to cage. If you want to move mealworms out of a shared tray, a window-mounted dish is the simplest step, since it is close to glass where larger birds are less willing to feed.

Should I feed mealworms all year?

No. The two periods when a dish earns its keep are a cold wet spell in spring, when flying insects vanish and bluebirds have nestlings, and a hard freeze in winter for birds like Carolina wrens that do not switch to seed easily. In warm, dry, insect-rich weather a dish adds little and mostly trains birds to queue for you. Stopping is safe: adults return to hunting the same day.

Sources and further reading

1. Feeding Birds Cornell Lab of Ornithology, Project FeederWatch Food types and the species each attracts
2. NestWatch Cornell Lab of Ornithology Nesting-season behavior and nestling provisioning
3. Eastern Bluebird Cornell Lab of Ornithology, All About Birds Diet and foraging behavior
4. Attract Birds National Audubon Society General guidance on supplementary feeding