Feeder Types

Mealworm Feeders

A mealworm feeder is the one feeder where the food walks away if you get the geometry wrong. Two inches of smooth vertical wall is the whole design.

A mealworm feeder is a dish. What makes it a mealworm feeder rather than a bowl is that the walls are smooth and steep enough that a live mealworm, the larva of the darkling beetle (Tenebrio molitor), cannot climb out. Glass, glazed ceramic, and slick molded plastic all work. Wood, mesh and textured plastic do not, and neither does any dish shallower than about 1.5 inches (4 cm).

The second design question is who gets the worms. Left in the open, a bowl of mealworms is a gift to starlings, jays and house sparrows, which is why the most useful mealworm feeders are enclosed boxes with small entry holes that a bluebird will learn and a starling cannot use.

This page covers dish geometry, the real differences between live and dried worms, the enclosed designs aimed at the eastern bluebird (Sialia sialis), how much to put out, and how to keep the wrong birds from finding it.

Dish geometry, which is most of the job#

Three numbers matter.

Wall height: 1.5 to 2 inches (4 to 5 cm) minimum. Below that a mealworm can rear up and tip itself over the lip. Two inches is comfortable.

Wall angle: vertical or slightly inward. A sloped side is a ramp. Some dishes flare outward at the top, which is exactly wrong.

Surface: smooth and seamless. Glass and glazed ceramic are the gold standard. Smooth plastic works until it weathers and the surface goes chalky, at which point worms start escaping and the dish needs replacing. Avoid anything with an interior seam, a molded logo, or a textured non-slip base, because all three are climbing surfaces.

Dried worms do not escape, so any dish will hold them, but a shallow tray also lets wind scatter them and rain turn them to mush. The same deep smooth dish is still the better choice.

Live versus dried#

Start with live worms if you are trying to recruit birds that have never used a mealworm feeder. Once bluebirds or wrens are visiting daily, switching to dried worms usually works and cuts both cost and hassle considerably.

Enclosed bluebird feeders#

The classic design is a shallow box with clear acrylic or glass sides, a hinged roof, a smooth-floored tray inside, and a 1.5 inch (38 mm) round entry hole at each end. Bluebirds go in and out through the holes without hesitation once they have learned the feeder. Starlings, grackles, jays and doves cannot fit or will not commit to entering an enclosed space.

House sparrows can fit through a 1.5 inch hole, and often do. There is no hole size that admits a bluebird and excludes a house sparrow, so the answer there is management rather than geometry, covered in controlling house sparrows at feeders.

Teaching a pair to use one takes patience and a fixed sequence:

1. Week one: feeder open, roof propped or sides off, worms plainly visible on top of the box.
2. Week two: roof down, entry holes uncovered, a few worms still on the roof as a signpost.
3. Week three: worms inside only, offered at the same time each morning.

Site the feeder within 30 to 50 feet (9 to 15 m) of an active nest box and in the open, since bluebirds hunt from exposed perches rather than from cover. Box siting is in nest boxes: sizing and siting, and the broader habitat argument is in how to attract bluebirds.

Other designs worth knowing#

Open dish on a pole or deck rail. Simplest and cheapest, and the right choice if starlings are not a problem where you live. Add a dome baffle above it to keep rain out.

Caged dish. A dish inside a wire cage with 1.5 to 2 inch (4 to 5 cm) mesh, which admits chickadees, wrens and titmice while excluding larger birds. The same principle as any caged and selective feeder, and it also stops squirrels.

Hanging cup with a dome. Good rain protection, poor selectivity. Fine in a yard without starling pressure, and the dome keeps dried worms from turning to paste in a downpour.

Window-mounted dish. Puts a Carolina wren about two feet from your face, which is worth arranging at least once.

Who else turns up#

Mealworms are close to universal among insect-eating feeder birds. Carolina wrens are often the first to find a new dish and the most reliable customers year-round. Chickadees and titmice take worms one at a time. American robins will hover awkwardly at a dish they cannot quite land on. Catbirds, warblers during migration, and woodpeckers all take them opportunistically.

The problem species are starlings and house sparrows. A European starling flock can empty a day's worms in under a minute, and once they have found the feeder they check it daily. Enclosed and caged designs are the answer; see also keeping starlings off feeders.

Rationing and timing#

Offer worms at a set time, once or twice a day, and stop when the portion is gone. Ten to fifteen worms per bird is a supplement. A pair of bluebirds with fledglings will happily take five times that if you let them, and that is where the cost and the nutritional concerns both start.

Keeping it clean#

Mealworms are wet, and a dish that holds worms also holds droppings, husks and rain. Live worms leave frass and cast skins; dried worms turn to paste when damp.

Rinse the dish every time you refill, tipping out the layer of bran and dust that settles in the bottom, and wash it properly with hot soapy water once a week, more often in summer. Enclosed feeders need the tray taken out and the interior wiped, since the roof traps humidity. The general method is in how to clean a bird feeder.

A mealworm routine that works#

• A glass or glazed ceramic dish, walls 2 inches (5 cm) deep, vertical and smooth.
• Live worms to recruit, dried and soaked once the birds are regulars.
• Offered at a fixed time each morning, one portion, no topping up.
• Live worms stored in the refrigerator on bran with a carrot slice, warmed to room temperature before serving.
• An enclosed or caged feeder if starlings are around.
• Sited in the open near a nest box for bluebirds, or on a deck rail for wrens.
• Rinsed at every refill, washed weekly.

Get those seven right and mealworms become the most predictable feeding you do. Bluebirds in particular learn a schedule within days, and a pair that has learned yours will be waiting on the wire before you open the door.