Species Comparisons • Backyard Identification
Eastern Bluebird vs Mountain Bluebird
Eastern Bluebird
Eastern Bluebird • Wikimedia Commons
Eastern Bluebird
Eastern Bluebird • Wikimedia Commons
Eastern Bluebird
Eastern Bluebird • Wikimedia Commons
Eastern Bluebird
Eastern Bluebird • Wikimedia Commons
Mountain Bluebird
Mountain Bluebird • Wikimedia Commons
Mountain Bluebird
Mountain Bluebird • Wikimedia Commons
Mountain Bluebird
Mountain Bluebird • Wikimedia Commons
Mountain Bluebird
Mountain Bluebird • Wikimedia Commons
Eastern Bluebird vs Mountain Bluebird (Sialia sialis vs Sialia currucoides): The Complete Backyard Identification Guide
Field Summary
Quick Answer: The Fastest Way to Tell Them Apart
Two bluebirds, one rusty, one not. Three rules:
- Male underparts: rusty breast = Eastern; all blue from throat to tail = Mountain.
- Map: East = Eastern; high open West = Mountain.
- Flight style: hovering like a kestrel over grassland = Mountain Bluebird.
At-a-Glance Comparison Table
The rusty-breasted bluebird and the sky-blue one, side by side. KEY rows separate fastest.
| Feature | Eastern Bluebird | Mountain Bluebird |
|---|---|---|
| Scientific Name | Sialia sialis | Sialia currucoides |
| Length | 6.5 in (16.5 cm) | 7.3 in (18.5 cm) |
| Wingspan | 12.2 in (31 cm) | 14.2 in (36 cm) |
| Weight | 1.0–1.2 oz (28–34 g) | 1.0 oz (30 g) |
| Overall Shape | Small, plump thrush with a round head and short bill | A slim, long-winged bluebird of open western high country |
| Male Plumage KEY | Brilliant royal blue above, rusty-orange throat and breast, clean white belly | Entirely sky-blue above and below, paler on the belly — no rusty anywhere |
| Female Plumage | Grayer blue above with blue wings and tail; duller rusty breast and white belly | Gray-brown with a blue rump, tail and wing edges |
| Bill Shape | Short, thin, dark | Thin, straight, black |
| Tail | Short, blue, slightly notched | Blue, medium length |
| Core Range KEY | East of the Rockies — meadows, orchards, open woods and nest-box trails | Breeds in western mountain meadows and sage flats; winters on southern plains |
| Migration KEY | Partial migrant; southern birds resident, northern birds withdraw in winter | Migrant; hovers low over open grass while hunting |
| Feeder Presence | Visits for live and dried mealworms and suet crumbles; nest boxes are the great attractant | Nest-box trails on open fence posts; live mealworms |
| Favorite Foods | Insects, wild berries and fruit; mealworms at feeders | Insects, caught by hovering; berries in winter |
| Song | A soft, musical series of whistled phrases — “cheer-cheerful-charmer” | A soft, warbling dawn song |
| Flight Call | A soft “chur-lee” and dry chatter | A soft, thin “few” |
| Population Trend | Recovered strongly thanks to nest-box campaigns; stable to increasing | Stable; benefits from nest-box programs |
Male Field Marks, Side by Side
Eastern Bluebird — Male
Sialia sialis
- Royal blue back and head with a rusty-orange breast.
- Clean white belly below the rust.
- Perches low and upright, scanning for insects.
Mountain Bluebird — Male
Sialia currucoides
- Entirely sky-blue — no orange anywhere.
- Hovers like a tiny kestrel over mountain meadows.
- Nests in boxes on open fence posts.
Female & Juvenile Marks, Side by Side
Eastern Bluebird — Female
Sialia sialis
- Gray-blue above with blue wings and tail.
- Paler rusty breast than the male.
- Accepts nest boxes readily — watch for carrying grass in spring.
Mountain Bluebird — Female
Sialia currucoides
- Gray-brown with blue wings, rump and tail.
- Chooses the nest cavity; male escorts.
- Hunts by hovering low over open grass.
Part-by-Part Anatomy Breakdown
Every part offers a check:
| Body Part | Eastern Bluebird | Mountain Bluebird |
|---|---|---|
| Male Breast | Rusty-orange | Sky-blue, no rust |
| Male Belly | White | Pale blue to whitish |
| Male Tone | Deep royal blue above | Pale turquoise-cerulean overall |
| Female | Gray with rusty breast wash, white belly | Plainer gray, blue mainly in wings and tail |
| Hunting Style | Perches low, drops to ground | Hovers in midair over open grass |
| Habitat | Pastures, orchards, nest-box trails | Mountain meadows, sagebrush, alpine edges |
| Song | Soft “cheer cheerful charmer” warble | A quiet, thrush-like warble, often pre-dawn |
Song & Call Comparison
Eastern Bluebird
Sialia sialis
Song: a soft, musical cheer-cheerful-charmer — gentle whistled phrases.
Calls: a soft chur-lee and dry chatter.
Eastern Bluebird voice • Wikimedia Commons
Mountain Bluebird
Sialia currucoides
Song: a soft, warbling dawn song, quiet and musical.
Calls: a soft, thin few.
Mountain Bluebird voice • Wikimedia Commons
Range & Seasonal Presence
The Eastern Bluebird lives east of the Rockies in open country with nest boxes and scattered trees.
The Mountain Bluebird breeds in high open country of the West — meadows, sagebrush and burned forest — wintering at lower elevations and into the Southwest. The two meet on the western Plains.
Feeder Behavior & Favorite Foods
- Eastern Bluebird: mealworms from a tray; boxes in mowed, open yards.
- Mountain Bluebird: mealworms at mountain cabins; boxes in open rangeland.
- Winter: both switch to berries — plant sumac, juniper and dogwood.
- Boxes: 1.5-inch entrance holes suit both; space boxes 100 yards apart.
Temperament & Flock Behavior
Eastern Bluebirds are gentle perch-and-drop hunters that tolerate close neighbors and reuse boxes.
Mountain Bluebirds are aerial — hovering over grasslands and dashing after insects, and migrating in loose flocks.
6-Step Backyard ID Checklist
- Male breast. Rusty = Eastern; all blue = Mountain.
- Male tone. Deep blue = Eastern; pale sky-blue = Mountain.
- Female. Rusty wash = Eastern; plain gray = Mountain.
- Map. East = Eastern; mountain West = Mountain.
- Hovering. Hovers while hunting = Mountain.
- Overlap zone. On the western Plains, check the breast carefully.
Frequently Asked Questions
How do you tell an Eastern from a Mountain Bluebird?
Male Easterns have a rusty-orange breast and white belly; male Mountains are entirely sky-blue with no rust. Females are grayer — rusty wash on Easterns, plain gray on Mountains.
Which bluebird hovers?
The Mountain Bluebird — it hunts by hovering over open ground like a tiny kestrel.
Do their ranges overlap?
Only on the western Plains; otherwise Easterns live east of the Rockies and Mountains live in the western high country.
Which is the bluest bluebird?
The male Mountain Bluebird — a luminous cerulean over the entire body.
Do both use nest boxes?
Yes — both are nest-box favorites; use 1.5-inch holes and open habitat.
What do bluebirds eat in winter?
Berries and small fruit — juniper, sumac and dogwood; mealworms at feeders any time.
Key Takeaways
- Male breast: Rusty = Eastern; all blue = Mountain.
- Tone: Deep = Eastern; pale sky = Mountain.
- Female: Rusty wash = Eastern; plain gray = Mountain.
- Map: East = Eastern; high West = Mountain.
- Hunting: Hovering = Mountain.
- Boxes: Both accept nest boxes.