How to identify the Blue Grosbeak

To correctly identify the Blue Grosbeak (Passerina caerulea), 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

14-17 cm (5.5-6.7 in)

Wingspan

26-29 cm (10.2-11.4 in)

Weight

26-31 g (0.9-1.1 oz)

Physical features to check

1. 1

   Plumage

   Overall feather coloration and pattern.

   Adult males are a deep, rich blue over most of the body, with two prominent rusty-brown wing bars. The lores (area between the eye and bill) are black. Adult females are largely warm brown, often with a bluish tinge on the rump and tail, and also possess two buffy or cinnamon wing bars. Immature males are a mottled blue and brown.

2. 2

   Beak shape

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

   Large, conical, and stout bill, dark gray to black in males, often paler on the lower mandible in females.

3. 3

   Eye color

   Iris color and any distinctive eye markings.

   Dark brown.

4. 4

   Leg color

   Leg and foot color.

   Dark gray to black.

5. 5

   Distinguishing features

   Standout features that separate this species.

   The large, conical bill and the two rusty wing bars are key distinguishing features for both sexes. The male's deep blue color is unique among similarly sized birds in its range.

6. 6

   Juvenile appearance

   How young birds differ from adults.

   Juveniles resemble females but are duller brown, often with faint streaking on the breast and less distinct wing bars. Young males gradually acquire blue plumage over their first year.

7. 7

   Seasonal changes

   Plumage variation between breeding and non-breeding seasons.

   No significant seasonal plumage changes in adults, though plumage may appear slightly duller due to wear by late summer. First-year males continue to molt into adult plumage during their first fall and winter.

8. 8

   Sexual dimorphism

   How males and females differ.

   Strong sexual dimorphism. Males are brilliant deep blue, while females are predominantly warm brown with some blue wash.

Key field marks

• Size and Shape. Look for a relatively large, chunky finch-like bird with a noticeably large, conical bill. It's larger than a sparrow but smaller than a robin.
• Male Plumage. The male's deep, rich, almost purplish-blue plumage is unmistakable. The two rusty-brown wing bars are a critical field mark, distinguishing it from the brighter, unbarred Indigo Bunting.
• Female Plumage. Female Blue Grosbeaks are warm brown, but always look for the two distinct buffy or cinnamon wing bars. They may also show a subtle bluish wash on the rump and tail, and their large bill is a good clue.
• Bill. The large, stout, conical bill is a key feature for both sexes and helps differentiate it from smaller-billed buntings.
• Song and Calls. Learn the male's rich, warbling song, which is more deliberate than an Indigo Bunting's. The sharp, metallic 'chink' call is also very distinctive and often heard even when the bird is hidden.
• Habitat. Look in brushy, overgrown areas, woodland edges, and fields with scattered shrubs. They prefer dense cover.

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