Species Comparisons • Backyard Identification
Mountain Bluebird vs Western Bluebird
Mountain Bluebird
Mountain Bluebird • Wikimedia Commons
Mountain Bluebird
Mountain Bluebird • Wikimedia Commons
Mountain Bluebird
Mountain Bluebird • Wikimedia Commons
Mountain Bluebird
Mountain Bluebird • Wikimedia Commons
Western Bluebird
Western Bluebird • Wikimedia Commons
Western Bluebird
Western Bluebird • Wikimedia Commons
Western Bluebird
Western Bluebird • Wikimedia Commons
Western Bluebird
Western Bluebird • Wikimedia Commons
Mountain Bluebird vs Western Bluebird (Sialia currucoides vs Sialia mexicana): The Complete Backyard Identification Guide
Field Summary
Quick Answer: The Fastest Way to Tell Them Apart
The sky-blue one and the rusty one. Three rules:
- Male rust: none at all = Mountain; rusty chest and shoulder patch = Western.
- Tone: pale sky-blue = Mountain; deep blue = Western.
- Hunting style: hovering over open grass = Mountain; perch-and-drop = Western.
At-a-Glance Comparison Table
The two western bluebirds, side by side. KEY rows separate fastest.
| Feature | Mountain Bluebird | Western Bluebird |
|---|---|---|
| Scientific Name | Sialia currucoides | Sialia mexicana |
| Length | 7.3 in (18.5 cm) | 6.3–7.5 in (16–19 cm) |
| Wingspan | 14.2 in (36 cm) | 11.4–13.4 in (29–34 cm) |
| Weight | 1.0 oz (30 g) | 0.8–1.1 oz (24–31 g) |
| Overall Shape | A slim, long-winged bluebird of open western high country | A plump, short-tailed thrush of open western woodland — perches low and drops to the ground for insects |
| Male Plumage KEY | Entirely sky-blue above and below, paler on the belly — no rusty anywhere | Deep blue head, back and tail; rusty chest, rusty flanks and a rusty patch across the upper back |
| Female Plumage | Gray-brown with a blue rump, tail and wing edges | Gray-brown with a white eye-ring, blue wings and tail, and a dull rusty breast |
| Bill Shape | Thin, straight, black | Thin, straight, dark |
| Tail | Blue, medium length | Short, blue in the male, blue-edged in the female |
| Core Range KEY | Breeds in western mountain meadows and sage flats; winters on southern plains | Open woodland, orchards and ranch country of the West, from British Columbia to Mexico |
| Migration KEY | Migrant; hovers low over open grass while hunting | Partial migrant — mountain breeders move to lower ground and south in winter |
| Feeder Presence | Nest-box trails on open fence posts; live mealworms | Live mealworms from a low tray; nest boxes on open posts |
| Favorite Foods | Insects, caught by hovering; berries in winter | Insects in summer; mistletoe and juniper berries in winter |
| Song | A soft, warbling dawn song | A short, soft, burry warble |
| Flight Call | A soft, thin “few” | A soft “few” or “kew” note |
| Population Trend | Stable; benefits from nest-box programs | Stable; benefits from nest-box programs |
Male Field Marks, Side by Side
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.
Western Bluebird — Male
Sialia mexicana
- Blue above with a rusty chest AND rusty back patch.
- Deeper, duskier blue than a Mountain Bluebird.
- Perches on fences and drops to the ground for insects.
Female & Juvenile Marks, Side by Side
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.
Western Bluebird — Female
Sialia mexicana
- Gray-brown with a white eye-ring and blue wings and tail.
- Dull rusty breast band.
- Accepts nest boxes readily — clean them between broods.
Part-by-Part Anatomy Breakdown
Every part offers a check:
| Body Part | Mountain Bluebird | Western Bluebird |
|---|---|---|
| Male Underparts | Entirely sky-blue | Rusty chest and flanks, gray-blue belly |
| Male Back | Blue, no rust | Blue with a rusty shoulder patch |
| Male Tone | Pale, luminous cerulean | Deep, rich blue |
| Female | Plain gray, blue in wings and tail | Gray-brown, eye-ring, dull rusty breast band |
| Hunting Style | Hovers like a kestrel over grassland | Perches low, drops to the ground |
| Habitat | Mountain meadows, sagebrush, burns | Open pine-oak woodland, ranch country |
| Song | Quiet thrush-like warble, pre-dawn | Soft burry warble at dawn |
Song & Call Comparison
Mountain Bluebird
Sialia currucoides
Song: a soft, warbling dawn song, quiet and musical.
Calls: a soft, thin few.
Mountain Bluebird voice • Wikimedia Commons
Western Bluebird
Sialia mexicana
Song: a soft, burry warble, mostly at dawn.
Calls: a quiet few note keeps pairs in touch.
Western Bluebird voice • Wikimedia Commons
Range & Seasonal Presence
The Mountain Bluebird breeds in high, open country of the West — meadows above the treeline edges, sagebrush and recent burns — wintering low and south.
The Western Bluebird lives lower, in open oak and pine woodland of the Pacific and interior West. They overlap in middle-elevation open forest.
Feeder Behavior & Favorite Foods
- Mountain Bluebird: mealworms at mountain homes; boxes in open rangeland.
- Western Bluebird: mealworms and boxes in open woodland and ranch yards.
- Winter: both flock to juniper and mistletoe berries.
- Boxes: 1.5-inch holes suit both; face them across open ground.
Temperament & Flock Behavior
Mountain Bluebirds are aerial hunters of big open country — hovering, dashing, and migrating in loose flocks.
Western Bluebirds are perch-and-drop birds of woodland edges, sedate and confiding around ranch yards.
6-Step Backyard ID Checklist
- Male rust. None = Mountain; chest + shoulders = Western.
- Tone. Pale sky = Mountain; deep blue = Western.
- Female. Plain gray = Mountain; rusty breast band = Western.
- Hunting. Hovering = Mountain; perch-and-drop = Western.
- Elevation. High open = Mountain; lower woodland = Western.
- Belly. Pale blue-white = Mountain; gray-blue = Western.
Frequently Asked Questions
How do you tell a Mountain from a Western Bluebird?
Male Mountains are entirely sky-blue with no rust. Male Westerns have a rusty chest, rusty flanks and usually a rusty shoulder patch. Mountains are also paler blue and hover when hunting.
Which bluebird hovers?
The Mountain Bluebird — it hunts by hovering over open grassland, kestrel-style.
Which lives higher?
The Mountain Bluebird — meadows and open slopes at elevation; Westerns keep to lower open woodland.
Do females differ?
Yes — female Mountains are plain gray with blue wings and tail; female Westerns show a dull rusty breast band and eye-ring.
Do both use nest boxes?
Yes — identical boxes work; Mountains use boxes across open rangeland, Westerns in open woodland.
Do they winter together?
Often — mixed bluebird flocks roam juniper and mistletoe country in the Southwest in winter.
Key Takeaways
- Male rust: None = Mountain; chest + back = Western.
- Tone: Pale sky = Mountain; deep = Western.
- Female: Plain gray = Mountain; rusty band = Western.
- Hovering: Hovers = Mountain.
- Elevation: Higher = Mountain; lower = Western.
- Boxes: Same box, different habitat.