Birds · Side by side
Eastern Bluebird vs Mountain Bluebird
How to tell them apart
Quick answer
Check the breast: a male eastern bluebird has a rusty-orange throat and breast under deep blue upperparts, while a male mountain bluebird is sky-blue all over with no orange. Females follow the same rule: eastern females have an orange-washed breast, mountain females a gray one.
Eastern and mountain bluebirds are close cousins in the thrush family: both are small cavity nesters that hunt insects in open country, and both have come back with help from nest-box volunteers. They mostly live on opposite sides of the Rockies, but they meet on the western Great Plains, and western strays of either species can confuse birders. Here is how to tell them apart.
Key differences
| Trait | Eastern Bluebird | Mountain Bluebird |
|---|---|---|
| Adult male | Deep royal blue above, rusty throat and breast, white belly | Sky-blue to turquoise all over, paler below, no orange |
| Female | Gray-brown with blue wings and an orange-washed breast | Gray with blue wings, rump and tail; gray breast |
| Shape | Shorter wings and tail, rounder look | Longer wings and tail, slimmer look |
| Hunting style | Drops to the ground from low perches | Often hovers over open ground before pouncing |
| Range | East of the Rockies, plus highlands south to Nicaragua | Western North America, Alaska to New Mexico |
| Habitat | Farms, orchards, open woods, parks and golf courses | Sagebrush, prairie, burns and alpine meadows |
| Nest-box entrance | 1 1/2 in (1 9/16 in also accepted) | 1 9/16 in |
| State bird of | Missouri and New York | Idaho and Nevada |
Where you will find each
Eastern bluebirds live from southern Canada to the Gulf Coast east of the Rocky Mountains, with separate populations in southeastern Arizona, the Mexican highlands and Central America. Mountain bluebirds breed from Alaska and the Yukon south through the Rockies, the Great Basin and the Sierra Nevada, and winter in the Southwest and Mexico. The overlap zone is the western Great Plains. In winter, mountain bluebird flocks sometimes wander east across the Plains, and single strays have reached the Atlantic Coast, so a pale, all-blue bluebird in the East is worth a careful look.
Hybrids and the third bluebird
Where their ranges overlap, eastern and mountain bluebirds occasionally pair up and produce hybrids with mixed features, so an odd-looking bluebird on the Plains may not fit either species neatly. In the West the real source of confusion is often the western bluebird. Male westerns are deep blue like an eastern but have a blue throat and usually a rusty patch across the upper back; they favor open pine and oak woodland rather than the wide-open sage and meadows that mountain bluebirds prefer.
Nest boxes for both
Both species readily use nest boxes on posts in open grassy ground, mounted about five feet up with a predator guard and checked weekly during the nesting season. Eastern bluebirds fit a 1 1/2-inch round entrance. The North American Bluebird Society says a 1 9/16-inch round hole is acceptable for all three bluebirds and recommends it wherever mountain bluebirds nest. Either size keeps out nearly all European starlings, the main competitor for bluebird cavities along with house sparrows and tree swallows.
By the numbers
The traits the daily bird game compares for each.
| Clue | Eastern Bluebird | Mountain Bluebird |
|---|---|---|
| Group | Thrushes | Thrushes |
| Colors | Blue, Orange, White | Blue |
| Habitat | Grassland | Grassland |
| Region | Eastern | Western |
| Length | 7 in | 7 in |
| Wingspan | 11 in | 13 in |
| Diet | Insects | Insects |
FAQ
Can eastern and mountain bluebirds interbreed?
Yes, occasionally. Mixed pairs and hybrids turn up where the two ranges overlap on the western Great Plains, though it is uncommon.
Which bluebird is the bluest?
The male mountain bluebird is blue from head to tail with no orange at all. The male eastern bluebird is a deeper, darker blue above but has a rusty breast.
What nest-box hole works for both bluebirds?
A 1 9/16-inch round entrance. The North American Bluebird Society accepts it for all three bluebird species, and it still excludes nearly all starlings.
Do mountain bluebirds ever show up in the East?
Rarely. Winter flocks sometimes drift east across the Great Plains, and lone strays have been found as far as the Atlantic Coast.
Could you tell them apart from a few clues? Test yourself in today's puzzle.
Play the daily bird game