Bluebirds are popular and easily recognized songbirds found across much of North America. There are three species of bluebirds in North America: the Western Bluebird, the Mountain Bluebird, and the Eastern Bluebird. The Western and Eastern Bluebirds look very similar and can be difficult to distinguish from one another, especially for beginning birders. However, with a bit of practice, several key differences can help identify whether you’re looking at a Western or an Eastern Bluebird.
Range and Habitat
The ranges of the Western and Eastern Bluebirds provide the first clues. As their names suggest, Western Bluebirds live in the western half of North America, while Eastern Bluebirds occupy the east. Understanding their ranges helps narrow down the possibilities of which species you might be seeing.
More specifically, Western Bluebirds breed west of the Rocky Mountains from southeastern Alaska and western Canada south to Mexico. They winter as far south as Guatemala. Eastern Bluebirds breed east of the Rocky Mountains from southern Canada to the Gulf states and southeastern Arizona. They winter along the Gulf Coast, southern Atlantic coast, and south to Nicaragua.
The two species overlap and potentially interact along the front range of the Rockies from Texas to Montana. They also both occur in central California. Anywhere in these overlap zones, habitat preferences must be considered along with other identification features.
Western Bluebirds occur in open woodlands, forest openings, parks, pastures with scattered trees, mountain meadows, and other open habitats interspersed with trees and shrubs. Eastern Bluebirds favor more open habitats like pastures, old orchards, cemeteries, parks, and suburban yards. Both species often use fences and powerlines as perching sites when hunting insects.
Understanding the preferred habitats of each species in different parts of the country can lend clues as to which species is more likely to occur. For example, bluebirds found in mountain meadows of Colorado are almost certainly Western Bluebirds. Meanwhile, bluebirds spotted in a Georgia pasture are most likely Eastern Bluebirds.
Plumage Differences
Plumage differences provide some of the best features to distinguish Western from Eastern Bluebirds. Males of both species have mostly blue plumage on their heads, wings, backs, and tails. However, several subtle differences are apparent upon close inspection.
The most obvious difference is on the breast. Adult male Western Bluebirds have a reddish-brown throat and breast. Their coloration transitions sharply from the blue throat to the rusty breast. Male Eastern Bluebirds, in contrast, have a uniform brick-red to rose-red breast and throat. The red coloring transitions more gradually into the blue on the nape area.
The blue coloring on Western Bluebirds also tends to be brighter and more electric looking. Eastern Bluebirds appear darker blue, almost a midnight blue shade. The back and wing feathers of Easterns may even look blackish in some light conditions.
In flight, Eastern Bluebirds show large white patches on their tail feathers and wings. This white is very noticeable when they fly. Western Bluebirds lack any bright white patches, appearing all blue when flying.
Females and juveniles of both species display much more subtle plumage differences:
– Female Western Bluebirds are pale blue-gray on the head, wings, back and tail. Their throats and breasts show a pale dusty orange or peach coloring.
– Female Eastern Bluebirds are similar but the gray coloration is darker slate-gray. Their orange breast and throat colors are also duller than female Westerns.
– Juvenile Western Bluebirds resemble adult females but with even duller plumage. Their throats and breast show diffused streaking.
– Juvenile Eastern Bluebirds are plain grayish overall with a faint orange wash on the throat and breast.
When differentiating female and juvenile birds, range and habitat remain important clues. But the brighter facial hues of Western Bluebirds are often apparent with good views. Eastern Bluebirds show duller, grayer faces.
Behaviors
Bluebirds exhibit several behavioral differences that can aid identification:
– Western Bluebirds frequently hover when hunting insects. Eastern Bluebirds rarely hover.
– Western Bluebirds perch on exposed branches with erect, upright postures. Eastern Bluebirds seem weaker-perched and often sit hunched over.
– Eastern Bluebirds are sometimes passive at feeders, tolerating close presence of other birds. Westerns are more territorial and chase away other species.
– Eastern Bluebirds have a disjointed, stuttering song. Western Bluebird songs sound smoother and more lyrical.
– Eastern Bluebirds are migratory, traveling south in winter. Western Bluebirds are often permanent residents, staying year-round in their breeding range.
None of these behaviors are definitive for identification on their own. But combined with plumage and range differences, behaviors can help confirm the identification in questionable cases. Familiarity with the typical behaviors of each species aids recognition in brief encounters.
Measurements and Shape
Subtle differences in body shape and proportions exist between Western and Eastern Bluebirds. These features require side-by-side comparison and may be difficult to apply in the field. But careful measurement and study of museum specimens show:
Feature | Western Bluebird | Eastern Bluebird |
---|---|---|
Length | 6.5 – 7.5 in | 6.5 – 7 in |
Wingspan | 10.5 – 13 in | 10 – 12.5 in |
Bill length | 0.9 – 1.1 in | 0.8 – 1 in |
Tarsus length | 0.9 – 1.1 in | 0.8 – 1 in |
Tail shape | Slightly notched | Rounded |
On average Western Bluebirds are very slightly larger than Easterns in length and wingspan. They also have a marginally longer bill and legs. Western Bluebirds tend to appear more elongated and slender overall. Their tails are marginally longer and appear notched at the tip. Eastern Bluebird tails are rounded-tipped.
These subtle structural differences are apparent with direct comparison of the two species side by side. But they can be difficult to discern in casual field observations. Still, with practice the more elegant shape of Westerns becomes somewhat apparent compared to the chunkier, sturdier profile of Easterns.
Voice
The songs and calls of Western and Eastern Bluebirds also differ. However, the vocalizations are complex with much variation. Differentiating the two species by voice alone is unreliable without substantial experience.
Some key points about the voices of each species:
– Western Bluebird songs are warbling and melodious, described as sounding like “chur lee chur lee”. Their calls include “chur” notes and fast “cherwee” calls.
– Eastern Bluebird songs are more disjointed and burry, often transcribed as “tur-a-lee”. Calls sound buzzier and raspier, like “chirrr” notes.
– Western Bluebird songs tend to be more musical and flow together into a melodic warble. Eastern Bluebird songs sound more fractured and chopped up.
– Eastern Bluebirds have a distinctive alarm call: a fast series of towhee-like “pips”. Western Bluebirds do not make this call.
– Western Bluebirds sometimes include mimicked songs of other species in their own songs. Eastern Bluebirds do not mimic other birds in their vocalizations.
Overall Western Bluebird vocalizations sound more lilting and melodious. Eastern Bluebird calls and songs tend to be harsher and more mechanical sounding to human ears. But there is much variation within each species. Their voices should not be used as the sole basis of identification without strong familiarity.
Geographic Variation
No consistent differences occur across the ranges of Western and Eastern Bluebirds. However, Western Bluebirds show subtle north-south variation:
– Northern populations are brighter blue above with more contrasting rufous underparts.
– Southern populations appear duller with more muted gray-blue coloring above and lighter peachy-orange below.
Despite these trends, variation exists across all populations. No subspecies are currently recognized. And plumage variation does not reliably indicate geographic origin.
Eastern Bluebirds exhibit very little geographic variation across their extensive range. No subspecies are recognized. So Eastern Bluebirds basically appear the same across populations.
Hybridization
Western and Eastern Bluebirds occasionally interbreed where their ranges meet in the Great Plains. The resulting hybrids show intermediate features:
– Males have medium blue upperparts and reddishthroats that gradually transition to pale orange breasts.
– Females appear pale bluish-gray above with pale peach-orange below.
– Song structure shows influences of both parent species.
– Behaviorally, hybrids often combine characteristics of each species.
Many bluebird hybrids go unnoticed and integrate into Western or Eastern flocks. Identifying hybrids requires finding intermediates of multiple features on the same bird. Knowledge of the overlap zone where both species occur aids identification of hybrids.
Conclusion
Distinguishing Western and Eastern Bluebirds provides a fun ID challenge for many birders. Their similarity and overlapping ranges make identification tricky. However, considering a combination of range, habitat, plumage, behaviors, measurements, and voice makes identification of most bluebirds possible in the field. Understanding the key differences allows appreciating these two beautiful and popular songbirds across the diverse areas they inhabit. Careful study and comparison will sharpen identification skills and build familiarity with the classic features of these two widespread North American bluebird species.