How to identify the Mountain Bluebird

To correctly identify the Mountain Bluebird (Sialia currucoides), check each of these features. Birds can be tricky: habit, habitat, and call often confirm a sighting that a single photo cannot.

Size at a glance

Length

15.5-18 cm (6.1-7.1 in)

Wingspan

33-35.5 cm (13-14 in)

Weight

28-32 g (1.0-1.1 oz)

Physical features to check

1. 1

   Plumage

   Overall feather coloration and pattern.

   Adult males are almost entirely brilliant sky-blue, often appearing iridescent. Adult females are duller, with a gray-brown body, pale blue on the wings and tail, and sometimes a faint blue wash on the rump. Juveniles are gray-brown with heavy spotting on the breast and back, and blue only on the wings and tail, gradually acquiring adult plumage.

2. 2

   Beak shape

   Shape and color of the bill: a key field mark.

   Slender, pointed, and relatively short; black in color.

3. 3

   Eye color

   Iris color and any distinctive eye markings.

   Dark brown

4. 4

   Leg color

   Leg and foot color.

   Black

5. 5

   Distinguishing features

   Standout features that separate this species.

   Males are unmistakable with their uniform, vibrant blue plumage. Females are distinguished from other bluebirds by the lack of rufous on the breast or flanks, and a generally paler, more grayish appearance with blue restricted to wings and tail. Their habit of hovering while foraging is also a key field mark.

6. 6

   Juvenile appearance

   How young birds differ from adults.

   Gray-brown overall with distinct white spotting on the breast and back, resembling a young thrush. Blue is restricted to the primary feathers and tail. They gradually molt into adult plumage.

7. 7

   Seasonal changes

   Plumage variation between breeding and non-breeding seasons.

   Plumage does not change significantly between breeding and non-breeding seasons, though fresh plumage may appear slightly brighter due to less feather wear.

8. 8

   Sexual dimorphism

   How males and females differ.

   Pronounced. Males are brilliant sky-blue all over, while females are much duller, primarily gray-brown with limited blue on wings and tail.

Key field marks

• Overall Color (Males). Look for a bird that is entirely brilliant sky-blue, with no rufous or white on the underparts. This is the most distinctive feature.
• Overall Color (Females). Observe for a bird that is predominantly gray-brown, with pale blue restricted to the wings and tail, and sometimes a faint blue wash on the rump. Absence of rufous on the breast/flanks is key.
• Foraging Behavior. Watch for their characteristic hovering flight over open ground, where they hang in the air before dropping to catch insects. This behavior is less common in other bluebird species.
• Habitat. Consider the location. Mountain Bluebirds prefer open, high-elevation habitats in western North America, often in meadows or sagebrush flats, whereas Western and Eastern Bluebirds prefer more wooded or suburban areas.
• Song/Calls. Listen for their soft, warbling, high-pitched song or their distinctive 'few' or 'chur' calls, which are generally softer than other bluebirds.

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