Bird Profile

Indigo Bunting

The male is not really a blue bird. He is a black bird that turns blue when the light hits him from the right direction, and the female is the plain brown bird almost nobody recognizes.

The male Indigo Bunting (Passerina cyanea) is not, strictly speaking, a blue bird. He is a dark brown bird carrying a structure in his feathers that scatters blue light back at you, which is why the same individual can look like a black silhouette on a wire at 6 a.m. and a piece of stained glass by nine.

He is small, about 5 inches (13 cm), roughly goldfinch-sized, with a stubby silver-gray bill and no markings of any kind. The female is a plain warm brown bird that most people log as "some sparrow" and forget.

They are birds of brushy edges rather than lawns, and they use feeders in a narrow seasonal window: heavily for a week or two on arrival in spring, sporadically in late summer, and almost never in between. This profile covers identification including the confusion species, the physics behind the color, the two seeds that actually work, the nighttime migration that gets them killed at lit buildings, and what a yard needs to hold a pair through the summer.

How to identify an Indigo Bunting#

A breeding male is uniformly blue from bill to tail, a shade deeper and more violet on the head, with small black lores in front of the eye. No wing bars. No streaks. No white anywhere. The bill is short, thick and pale silver-gray, the shape of a seed cracker rather than an insect tweezer.

The female is the harder half of the job. She is plain warm brown above, buffier below, with soft blurry streaking on the breast, whisper-faint wing bars, and no eyebrow, eyeline, crown stripe or throat mark. Older females often carry a hint of blue in the tail, rump or wing coverts, which is the giveaway when you catch it.

Fall males are the third look. Through late summer and fall they molt into a brown, patchy plumage that keeps ragged blue blotches on the wings, tail and shoulders. A brown bird with random blue splotches in September is a young or molting male bunting and nothing else.

Confusion species#

Why the male looks black in poor light#

Almost no blue you see in a North American bird is a blue pigment. Indigo Bunting feathers contain melanin, the same dark pigment in a crow, and nothing else. Grind one up and the powder is brown.

The color comes from the architecture. Inside each feather barb is a spongy layer of keratin shot through with air pockets, spaced at a scale close to the wavelength of blue light. That layer scatters short wavelengths back toward the viewer while the melanin underneath absorbs everything that gets past it. The result is a saturated blue that exists only in reflected light.

So the direction of the light decides what you see. With the sun behind you and falling on the bird, the bunting blazes. Backlit against a bright sky, or in shade, or at dusk, there is nothing to scatter and you are looking straight at the melanin: black.

Where and when you will see them#

Indigo Buntings breed across the eastern and central United States and into southern Canada, west to about the Great Plains, where they meet and sometimes hybridize with the Lazuli Bunting. They winter in Mexico, Central America and the Caribbean, so the entire population leaves the US every fall.

The habitat is scruffy: old fields going to shrub, roadside thickets, brambles along a fence line, regenerating clearcuts, and power line rights-of-way. Forest clearing over the last two centuries handed them a great deal of new habitat. Deep woods and clipped suburban lawns hold none.

Feeder visits track arrival. Birds land in late April or early May, ahead of the insect and seed supply, and hit feeders hard for a week or two. Once they are on territory they switch to wild seed and insects and mostly vanish, then reappear in late summer with dependent young. Many yards get two good weeks a year, which is worth planning for as part of feeding birds during migration.

What they eat and the feeder setup that works#

The bill is built for grass and weed seed: foxtail, panic grass, smartweed, dandelion, plus buds and small fruit. During the breeding season the diet shifts heavily toward insects, and nestlings are fed almost entirely on caterpillars, small grasshoppers and spiders.

A nyjer or finch feeder already hung for goldfinches needs no modification. If you want a better shot, add a small tray or platform feeder with millet at 4 to 5 feet (1.2 to 1.5 m), sited within about 15 feet (4.5 m) of a hedge, bramble patch or brush pile. Buntings feed in short hops out of cover and will not cross open ground for seed.

Song and neighborhood dialects#

The song is a bright, high, paired series, each phrase delivered twice: often written as fire-fire, where-where, here-here. Males sing from exposed high perches, including wires and dead treetops, and they keep singing through the hot midsummer weeks when most songbirds have gone quiet. It is far and away the easiest way to find them.

Young males learn their song from established neighbors rather than from their fathers, so small patches of countryside share a distinctive local version. A song type can persist in one thicket across many generations of birds, which means the bunting singing at your fence line may be repeating a tune older than your house.

Migration by starlight#

Indigo Buntings migrate at night. Classic planetarium experiments in the 1960s showed that young buntings work out the center of rotation of the night sky during their first summer and orient relative to that, rather than fixing on any single star. It remains one of the cleanest demonstrations of star navigation in birds.

The cost of being a night migrant is collision. Lit windows and illuminated towers pull migrating songbirds off course and hold them circling, and buntings turn up regularly in spring and fall building-strike counts.

Nesting#

The female builds alone, weaving a compact cup of leaves, grass and bark strips 1 to 3 feet (0.3 to 1 m) up in a blackberry tangle, dense shrub or sapling at a field edge. The clutch is usually 3 to 4 unmarked white to very pale blue eggs.

She incubates for about 12 to 13 days and does most of the feeding. Young leave the nest at roughly 9 to 12 days, often before they can fly well, and stay hidden in dense low cover while the male sometimes takes over their care and the female starts a second brood. Two broods a season is normal in the middle of the range.

Nests low in shrubby edge habitat are heavily used by brown-headed cowbirds, and bunting pairs raise a substantial number of cowbird chicks.

Population and conservation#

Indigo Buntings remain one of the most abundant songbirds of eastern edge habitat and carry no conservation listing. Long-term survey trends are broadly stable, with gradual declines in some regions as old fields grow into closed forest or are developed outright.

The yard-level hazards are the ordinary ones plus one specific to night migrants: window and tower collisions in spring and fall, outdoor cats hunting birds that nest 2 feet (0.6 m) off the ground, and the insect decline that shows up in a lawn treated with broad-spectrum products, discussed in pesticides, lawns and birds.

A yard that holds indigo buntings#

• Nyjer and white millet out by mid to late April, before the first birds arrive.
• A shrubby, unmown edge somewhere on the property: brambles, a hedgerow, a corner left alone. See native plants for birds.
• Feeder within 15 feet (4.5 m) of cover, at 4 to 5 feet (1.2 to 1.5 m).
• Water, especially a shallow basin with movement, which pulls in buntings that ignore seed.
• Lights off at night in migration months, and treated glass on the big windows.