Bird Profile
Eastern Bluebird
You cannot buy a bag of seed that attracts bluebirds. What attracts them is a mealworm dish, a correctly built box with a 1.5 inch hole, and a baffle under it.
The short answer
- Eastern Bluebirds do not eat seed. Mealworms, a nest box and open grassy ground are what bring them in.
- The entrance hole must be 1.5 inches (3.8 cm). Larger lets starlings in, smaller keeps bluebirds out.
- Mount the box 4 to 6 feet (1.2 to 1.8 m) up on a smooth metal pole with a baffle. A box on a tree or fence post is a raccoon feeder.
- They hunt by dropping onto insects from a low perch, so they need mown or grazed open ground with scattered perches nearby.
- In winter they flock, switch largely to fruit, and roost together in cavities, which is when a heated water source matters more than food.
At a glance
- Scientific name
- Sialia sialis
- Length
- 6.3 to 8.3 in (16 to 21 cm)
- Wingspan
- 9.8 to 12.6 in (25 to 32 cm)
- Weight
- 1.0 to 1.1 oz (28 to 32 g)
- Range
- East of the Rockies, southern Canada to the Gulf and into Mexico. Resident in the South, migratory in the North.
- Favorite foods
- Mealworms, insects, small fruit and berries
- Best feeder
- Enclosed or open mealworm dish on a pole
- At feeders
- Year-round in the South, in flocks during winter cold snaps
The Eastern Bluebird (Sialia sialis) is a small thrush about 7 inches (18 cm) long: the male deep blue above with a rusty orange throat and breast and a white belly, the female the same pattern in muted gray-blue and buff. It eats insects and fruit, not seed, and it nests in cavities.
Those two facts define everything about attracting them. No feeder full of sunflower will ever bring in a bluebird. A shallow dish of mealworms next to a properly built box on a baffled pole, overlooking mown ground, will.
This profile covers identification, where and when to expect them, the mealworm setup that works and how much to offer, exact nest box dimensions and siting, the predator guards that decide whether a brood survives, and what changes in winter.
How to identify an Eastern Bluebird#
Male: brilliant royal blue on the head, back, wings and tail, with a rusty orange throat, breast and flanks and a clean white lower belly and undertail. In flat light the blue can look almost black; in sun it is unmistakable.
Female: gray-brown head and back with blue washing the wings and tail, a paler orange breast, and a thin white eye ring.
Juvenile: heavily spotted gray-white breast, blue in the wings and tail, and an obvious eye ring. The spotting marks it as a thrush and confuses a lot of people in July.
Shape and posture help as much as color. Bluebirds are round-headed, short-billed and upright, and they perch quietly on wires, fence posts and low branches, scanning the ground below.
What it is not#
| Bird | How to tell it apart |
|---|---|
| Indigo Bunting | Entirely blue with no orange, and a thick conical seed bill |
| Blue Jay | Much larger, crested, white and black markings, noisy |
| Western Bluebird | Blue throat, not orange; a western bird with almost no range overlap |
| Mountain Bluebird | Pale sky blue with no orange at all; western mountains |
| Barn Swallow | Blue above and buff below, but slim, forked-tailed, and constantly in flight |
Range settles most of it. Across the East, a blue-and-orange bird on a fence wire is an Eastern Bluebird.
Where and when you will see one#
Eastern Bluebirds live east of the Rockies from southern Canada to the Gulf, and south into Mexico. They are year-round residents through most of the southern and central parts of that range and migratory in the North, where birds arrive in March and leave in October and November.
The habitat requirement is specific: open ground with short grass to hunt over, scattered low perches to hunt from, and cavities to nest in. Pastures, orchards, cemeteries, golf courses, roadsides and large lawns all qualify. A closed suburban yard with mature canopy and no open ground does not, however many boxes you put up.
Their hunting method explains the habitat. A bluebird sits on a perch 3 to 10 feet (1 to 3 m) up, watches the grass, then drops onto a beetle or cricket and returns. Tall or thick vegetation makes that impossible.
What Eastern Bluebirds eat#
Roughly two thirds of the annual diet is invertebrates: beetles, grasshoppers, crickets, caterpillars, spiders and, in season, a great many insect larvae. The rest is fruit, and the fruit share rises sharply from fall through late winter.
| Food | Bluebird interest | Notes |
|---|---|---|
| Mealworms | Very high | Live are preferred; dried work if soaked briefly in warm water |
| Native berries | High in fall and winter | Dogwood, sumac, holly, red cedar, serviceberry |
| Chopped fruit | Moderate | Blueberries, softened raisins, small pieces of apple |
| Suet crumbs or bluebird nuggets | Moderate in cold weather | Offer crumbled, not as a hanging block |
| Sunflower, millet, nyjer, corn | None | Bluebirds are not seed eaters |
Planting for fruit does more over a decade than any dish ever will. Red cedar, dogwood, sumac and serviceberry are the workhorses, and the wider case is in native plants for birds.
Ration the mealworms
Offer a set amount, roughly 10 to 15 mealworms per bird once or twice a day, and stop. An unlimited dish encourages pairs to feed mealworms to nestlings in place of a varied insect diet, and dried mealworms alone are a poor food for growing young. During nesting season, put out live worms or nothing.
The feeder setup that works#
Use a dish, not a hanging feeder. A shallow tray with sides about 1 inch (2.5 cm) high, on a pole 4 to 5 feet (1.2 to 1.5 m) up, in the open and within sight of a favored perch.
An enclosed mealworm feeder with 1.5 inch (3.8 cm) entrance holes in the sides is the upgrade. It lets bluebirds in and keeps mockingbirds, starlings and jays out, which otherwise clear a dish in a minute. Prop the door open for the first week so the birds learn there is food inside.
Getting them to notice takes patience. Put the dish where they already perch, offer at the same time each morning, and let the birds find it. Some people tap the dish or use a whistle at feeding time; bluebirds learn the cue within a couple of weeks.
Water is the other draw. A shallow bird bath with moving water pulls in bluebirds that will not touch a feeder, and in winter a heated bath is the strongest attractant in the yard.
Nest boxes: the numbers that matter#
Bluebird boxes fail for boring, fixable reasons: the wrong hole, the wrong mount, the wrong place.
| Spec | Eastern Bluebird box |
|---|---|
| Entrance hole | 1.5 in (3.8 cm), round, no perch |
| Floor | 5 x 5 in (13 x 13 cm) inside |
| Hole above floor | 6 to 8 in (15 to 20 cm) |
| Mounting height | 4 to 6 ft (1.2 to 1.8 m) |
| Mount type | Smooth metal pole with a baffle |
| Facing | Toward open ground, away from prevailing wind |
| Spacing | About 100 yd (90 m) between boxes |
| Access | Side or front panel that opens for monitoring |
The 1.5 inch (3.8 cm) hole is the load-bearing number. Anything larger admits European Starlings, which will kill adults and young to take a cavity. Anything smaller excludes bluebirds themselves.
Boxes need ventilation gaps under the roof, drainage holes in the floor, and unpainted or lightly stained untreated wood at least 0.75 inch (2 cm) thick. Never add a perch: bluebirds do not need one and it gives predators and House Sparrows a foothold. Broader guidance for every species is in nest boxes: sizing and siting.
Pairs raise two and sometimes three broods between March and August. Clutches are 3 to 7 pale blue eggs, occasionally white. Incubation runs about two weeks and young fledge at 17 to 21 days.
A box on a tree or wooden post will be raided
Raccoons, snakes and cats all climb wood easily. Mount on a smooth metal pole and fit a stovepipe or cone baffle directly beneath the box, and add a hole guard, a wooden block that deepens the entrance tunnel, to stop a raccoon reaching in. This single change does more for nesting success than anything else on the list.
Monitoring, competitors and the honest problems#
Open the box once a week during the season, briefly and in good weather. It does not cause abandonment, and it is the only way to catch problems early. Note eggs, young and anything wrong.
Three competitors show up repeatedly. House Sparrows are non-native, unprotected in the US, and will kill bluebirds in the box; their nests can legally be removed, and the tactics are in controlling House Sparrows at feeders. European Starlings are excluded by the correct hole size. House Wrens are native and protected, so the only remedy is siting bluebird boxes well out in the open, at least 100 feet (30 m) from shrub and woodland edge.
Blowfly larvae under the nest, and heat in an unventilated box in July, account for many of the remaining losses. Cats account for a good share of the adults, which is worth reading about in cats and birds.
Pair your boxes if you also have swallows
Two boxes mounted 15 to 25 feet (5 to 8 m) apart let a bluebird pair and a tree swallow pair each take one, because the swallows will not tolerate another swallow that close but will tolerate a bluebird. It converts a competitor into a guard against other swallows.
Winter bluebirds#
Northern breeders move south in fall, and the birds you see in January in the mid-Atlantic or the Southeast may not be the ones that nested there. Winter flocks of a dozen or more move together, feeding on fruit and roosting communally in cavities and boxes, sometimes with several birds packed into one box on a hard night.
Leave boxes up all winter and clean them out in fall; they get used as roosts. Keep water open, offer crumbled suet or a few soaked mealworms during ice, and expect bluebirds to show up in a yard that has ignored them all year.
A bluebird plan for the year#
- February to March: clean and repair boxes, check the baffle, confirm the hole is still 1.5 inches (3.8 cm).
- March to August: monitor weekly, remove House Sparrow nests, offer live mealworms in measured amounts.
- After each brood: remove the old nest so the pair can rebuild.
- September: plant native fruiting shrubs while the ground is warm.
- November to February: keep water unfrozen, leave boxes up for roosting, offer fruit and crumbled suet in cold snaps.
The full attraction sequence, including what to do if a box sits empty for two seasons, is in how to attract bluebirds.
Frequently asked questions#
What do you feed Eastern Bluebirds?
Mealworms, live or dried, plus fruit such as blueberries, chopped raisins soaked in water, and native berries. They eat almost no seed, so a standard sunflower or mixed seed feeder will not attract them. Offer about 10 to 15 mealworms per bird per day in a shallow dish rather than an unlimited supply.
What size hole does a bluebird house need?
A round hole 1.5 inches (3.8 cm) in diameter for Eastern Bluebirds. That size admits bluebirds and excludes European Starlings. Do not enlarge it, do not add a perch below it, and place it 6 to 8 inches (15 to 20 cm) above the box floor so nestlings cannot be reached from outside.
How high should a bluebird box be and where do I put it?
Mount it 4 to 6 feet (1.2 to 1.8 m) above the ground on a smooth metal pole fitted with a baffle, facing open mown ground, with a shrub, fence or low tree 25 to 100 feet (8 to 30 m) away for fledglings to reach. Avoid tree trunks and wooden fence posts, which give predators an easy climb.
Do Eastern Bluebirds stay all winter?
In the southern two thirds of the range, yes. Birds in the North and in Canada move south, and northern yards often see flocks appear only in hard weather. Wintering birds switch mainly to fruit, gather in loose flocks, and roost communally in cavities and boxes on cold nights.
How do I keep House Sparrows out of my bluebird box?
The 1.5 inch (3.8 cm) hole stops starlings but not House Sparrows, so the answer is siting and monitoring. Place boxes away from barns, feeders and buildings, out in open ground, and check them weekly. House Sparrows are non-native and unprotected in the US, so their nests may legally be removed, unlike those of native competitors.
Why did bluebirds build a nest and then abandon the box?
The usual causes are predation, House Sparrow or House Wren interference, heat, or repeated disturbance. A box in full afternoon sun without ventilation can cook a brood, a box on a tree trunk invites raccoons and snakes, and a stick-filled box means a wren claimed it. Weekly monitoring tells you which one happened.