Quick Answer
Bluebirds and eastern bluebirds are two similar but distinct species of thrush in the genus Sialia. The main differences between them are:
- Range – Bluebirds have a more western range, while eastern bluebirds are found in the eastern and central United States.
- Color – Male eastern bluebirds have a red-brown breast and blue upperparts, while male bluebirds have an all blue plumage.
- Behavior – Bluebirds are a bit more aggressive than eastern bluebirds when defending nests.
- Habitat – Eastern bluebirds prefer open woodlands, while bluebirds like more open areas like meadows and parks.
Despite these differences, bluebirds and eastern bluebirds have very similar body shapes, sizes, songs, and nesting behaviors. Telling them apart requires an understanding of their range and subtle plumage differences.
Detailed Comparison
Ranges
The most straightforward way to tell bluebirds and eastern bluebirds apart is by their general range:
- Bluebirds are found west of the Rocky Mountains across western North America.
- Eastern bluebirds live east of the Rockies in central and eastern parts of the United States.
There is a zone of overlap between the two species in some of the central plains states like Colorado, Wyoming, and Montana. But in general, birds found west of the Rockies will be bluebirds, while birds in the eastern half of the country are eastern bluebirds.
The map below shows the general ranges of these two similar species:
As you can see, bluebirds (shown in green) occupy terrain in the west, while eastern bluebirds (shown in purple) can be found in the central and eastern states.
Plumage
Male bluebirds and eastern bluebirds look different even though they both have blue feathers.
Male bluebirds have an all blue plumage on their head, wings, back, and tail. The only exception is some rusty coloration on the breast.
Male eastern bluebirds have a red-brown colored breast in addition to the blue coloration on their wings, head, and back. This gives them a distinctive blue above and reddish below appearance.
Females of both species are grayish-brown on the head and back with some blue in the wings and tail. Female bluebirds also tend to be a bit more colorful than female eastern bluebirds.
Here’s a quick comparison of the plumage:
Species | Male Plumage | Female Plumage |
---|---|---|
Bluebird | All blue except for rust breast | Gray-brown with some blue in wings |
Eastern Bluebird | Blue upperparts, rusty red breast | Grayish brown overall |
The main takeaway is that male eastern bluebirds have that colorful reddish breast that bluebirds lack. Females are trickier to distinguish visually.
Behavior
Bluebirds and eastern bluebirds share very similar behaviors. Here are some of their behavioral similarities:
- Both are cavity nesters that build nests in holes in trees or nest boxes put up by humans.
- They feed on insects like grasshoppers, crickets, and spiders as well as berries.
- males of both species sing beautiful, warbling songs to attract mates and defend territory.
- Bluebirds and eastern bluebirds are migratory, wintering in the southern United States or Mexico.
However, bluebirds tend to be a bit more aggressive than eastern bluebirds when defending nesting sites. Bluebirds will readily get into conflicts with other cavity nesters like tree swallows, whereas eastern bluebirds are more passive.
So while their behaviors are broadly similar, eastern bluebirds tend to be shyer and less inclined to get into squabbles over nesting territory.
Habitat
Both bluebird species prefer open habitats, but they have some habitat differences:
- Eastern bluebirds live in open woodlands with some clearings and sparse vegetation.
- Bluebirds prefer more open expanses like meadows, parks, and agricultural fields.
So eastern bluebirds like a mix of trees and clearings, while bluebirds simply need shorter grass and sparse vegetation around their nesting cavities.
You’re more likely to spot eastern bluebirds perched on fence posts or low branches in a rural woodlot. Bluebirds will perch on wires, posts, and rocks out in open fields and pastures.
Nest Box Designs
Bluebirds and eastern bluebirds have slightly different preferences when it comes to artificial nest boxes put up to attract them:
Bluebird nest box design:
- 1.5-1.75 inch diameter entrance hole
- At least 4×4 inch floor
- No perch
- Deep enough to discourage other species
Eastern bluebird nest box design:
- 1.5 inch diameter entrance hole
- At least 5×5 inch floor
- Small perch below hole
- Shallower depth okay
So bluebirds do best with a bit larger entrance hole and no perch, while eastern bluebirds like a smaller entrance and a perch. Eastern bluebirds will also use more shallow nest boxes.
Following these guidelines when putting up nest boxes will better attract the desired species in a given area.
Identification Tips
Here are some quick tips for identifying eastern bluebirds vs. bluebirds in the field:
- Check the range – Eastern in the east, bluebirds in the west
- Look for the rusty red breast on males – Present in eastern bluebirds, absent in bluebirds
- Note habitat – Eastern in semi-open woods, bluebirds in fields/meadows
- Consider behavior – Eastern less aggressive around nest
Eastern bluebirds are unique among the bluebirds for their red breast and their mix of woodland and open habitat preferences.
Getting a quick look at plumage on the male is usually the simplest way to determine if you’re looking at an eastern bluebird or bluebird. The all blue plumage indicates a bluebird, while the red breast signals an eastern bluebird.
Conclusion
In summary, bluebirds and eastern bluebirds appear very similar but have some distinct differences:
- Eastern bluebirds have red-brown colored breasts, while bluebirds have all blue plumage.
- Bluebirds live west of the Rockies, eastern bluebirds in the eastern half of the U.S.
- Eastern bluebirds prefer semi-open woodlands, bluebirds like more open areas.
- Eastern bluebirds are less aggressive around nest sites.
So while they share vibrant blue feathers and songs, the ranges, subtle plumage differences, habitat preferences, and behaviors of bluebirds and eastern bluebirds set them apart as distinct species. Careful observation and noting field marks like the rusty breast are needed to distinguish these two colorful thrushes.