From coast to coast of the United States, the Blue Grosbeak is a regular summer resident in dense thickets along streams. Most common in the south, they have spread north in recent decades. They now regularly breed as far north as New Jersey, Ohio and North Dakota, and migrants move as far north as Canada in spring and fall. Birdwatchers around the world therefore have reason to think about identifying them.
For many years, this grosbeak was classified as a separate genus. He is now placed among the Passerine buntings, as well as indigo, lazuli, painted and variegated buntings. Although the Blue Grosbeak can be distinguished after enough practice, it is easy to confuse this species with the Indigo Bunting, so this column will focus on comparing these two species.
Adult males in breeding plumage are the easiest to separate. Male Indigo Buntings are only blue in spring and summer, moulting to predominantly brown plumage for the winter, while adult male Grosbeaks are blue year-round. Grosbeak has rich rufous-chestnut wingbars, the upper one being very broad. Young male Indigo Buntings may be mostly blue with brown wings, including brown wingbars, but they never approach the full grosbeak pattern. Also, male grosbeaks have black on the face around the base of the bill, which is not the case on the sparrow.
Thus, adult males in spring and summer can be recognized at a glance by markings alone. But to improve your identification skills, it’s important to do more than just peek. Take the time to study these birds carefully and memorize their shapes, as shape aspects are the best way to identify the species in other plumages.
The Indigo Bunting could be described as having the shape of a “normal” bird, with no unusual appearance. The Blue Grosbeak, however, is quite distinctive. Its beak is large and deep at the base; the pale base of the thick lower mandible makes its size more evident. It has a large head (as large-billed birds usually do) and a stocky body. The grosbeak’s general build can make its tail appear relatively short, although this is partly an illusion. The tail is square or slightly rounded at the tip, not indented like that of the sparrow, and often appears broad. This wide-tailed effect can be noticeable if you look for it.
In the female Blue Grosbeak, the wing pattern is the main terrain mark, besides the shape. They always have contrasting wingbars, ranging from buff to reddish brown, and the upper wingbar is usually wider and more colorful than the lower one. The back may show broad fuzzy streaks, while the chest is not marked with brown. Female Indigo Buntings, in comparison, have solid brown backs and fine streaks on the breast. However, juvenile Blue Grosbeaks may show faint streaking on the breast, and streaking may be lacking in Indigo Buntings with worn plumage, so this is not a diagnostic feature in itself.
What to look for
The size and the shape. A medium to small-sized but stocky songbird with a very large beak, large head, stout body, and broad, square-tipped tail.
Wing bars. Two prominent wingbars; the upper part (tips of the median coverts) is generally wider and more richly colored than the lower part (tips of the greater coverts).
Face model. The male has black feathers at the base of the beak. The female has a very plain brown face, contrasting with the pale base of the thick lower mandible.
Body plumage. Adult male entirely blue, darkened with brown feather tips in fall. The young male wears a mixture of brown and blue. The female is brown with blue highlights and has fuzzy stripes on the back but no streaks on the chest.
Grosbeak, female, April in Galveston County, Texas
The female Blue Grosbeak is a subtle bird, with only hints of blue on the shoulder, rump and tail. The general color of the body varies from warm brown to dull grey-brown; the color is often richer on the head. The wingbars are always quite conspicuous, varying from a dull buff-brown (as on the bird in this photo) to a cinnamon-brown or brighter maroon. Fuzzy streaks are sometimes visible on the back, while the breast is smooth and without streaks; the female Indigo Bunting has a plain back and finely streaked chest. Despite these subtle differences in the markings, the form elements are the most important for identification. The grosbeak’s thick bill, large head, and stocky body are among its best marks in the field.
Indigo bunting, female. April in Galveston County, Texas.
Few birds can compete with a female Indigo Bunting because of her purely brown color. None of our sparrows are so devoid of markings. This simplicity, along with the details of form, can help define identity. The bird has wingbars, not very visible but always present except in some late summer birds with very worn plumage. The wingbars may even appear buff, reminiscent of the pattern of a female Blue Grosbeak. Usually their color is barely different from that of the rest of the wing. Fine streaks on the chest are usually present but may be difficult to see, as in this individual. And on closer inspection, a tint of blue often appears on the tail, shoulders, and elsewhere.
Grosbeak, young male. April in Galveston County, Texas.
In spring, yearling male Grosbeaks are quite variable, with almost any combination of blue and brown on the body plumage, but it is very common for them to have the blue feathers concentrated on the head and Chest. Their wing pattern isn’t always as striking as on the bird in this photo, but they still exhibit warm chestnut wingbars, with the upper usually more deeply colored than the lower. They usually show at least a few black feathers around the base of the beak, which Indigo Buntings lack. But some have only a little blue in the plumage and little contrast in the wings, so solid identification will rely on the bird’s distinctive shape.
Indigo Bunting, young male. April in Galveston County, Texas
As with Blue Grosbeak, yearling male Indigo Buntings have extremely variable body plumage, ranging from almost entirely brown to almost entirely blue. It is common for them to show narrow, contrasting brown wingbars, but these should not be confused with the broader, more colorful wingbars of the grosbeak. If in doubt, the two species can be separated by their different shapes; the sparrow never matches the huge-billed, big-headed, thick-bodied silhouette of the grosbeak. Among other minor points of shape differences, the Blue Grosbeak often appears to have a broader tail than the Indigo Bunting, but when the Sparrow spreads its tail (as the one in the photo does), this difference is obscured.
late and early
Although I have seen Blue Grosbeaks in many places, my lasting impressions come from southeastern Arizona. There they have a different timing. In most southern states, from the Gulf Coast to southern California, spring Grosbeak migrations can be expected in April. This is true even in western Arizona. But in southeastern Arizona, they can be hard to find in April, and they might not be around in large numbers until late May.
Apparently, they don’t need to rush to grab the best territories. Although some begin building their nests in May, their main breeding season in this area is in late summer. In the southeastern Arizona Lowlands, June is the hottest and driest month. The summer rains begin in July and in August the valleys are green again. Grosbeaks actively raise their young during this green season, and some pairs may not fledge until September.
These late summer breeders can be precocious in one way: as morning singers. A few times I’ve been to a prime habitat in southeastern Arizona, well before dawn in August, and found these grosbeaks to be among the first birds to sing. When a hint of light touched the eastern horizon, the rich, hoarse chirps of male Grosbeaks came from far and near in the thickets. Eventually, other species intervened. I’ve always wondered: are grosbeaks such early singers elsewhere, or is that just a trait of Arizona?