At a diminutive 4½ inches (although tending on the plump side), the Indigo Bunting is a bit of a gender-linked Jekyll and Hyde. Breeding males are a gorgeous indigo blue, with a slight purple cast on their heads and a smattering of black on their wings; females, just plain, mousy brown with a hint of buffy wing bars. (Winter and first-spring males are a mixture of brown and blue, just to keep you guessing.)
Indigo Buntings prefer to breed in shrubs and brush that grow along rivers and creeks, roads, agricultural fields, and forest edges. They have bred throughout the eastern U.S. and southern Canada for a long time. But this species began to expand its range westward in the 20th century, due in part to tree plantings, fire suppression, and water impoundments that allowed willows and non-native tamarisks to expand around western rivers.
An Indigo Bunting’s diet varies by season. In winter, they dine on small seeds and berries, buds, and insects. While migrating, they opt mainly for grass and weed seeds. (During migration, even if you don’t live anywhere near their desirable breeding habitat, you may spot one at your seed feeders.) Summer fare includes small spiders and insects, berries, and, only occasionally, seeds.
Most Indigo Buntings winter far south, stretching from Florida and southern Texas to Panama. They begin to arrive in Colorado in early May. Once he has established a territory and convinced a female to stick around, the male contributes only the absolute minimum to the breeding effort. The female builds the nest, incubates the eggs (usually 3 or 4), and broods the young (which hatch after 12 or 13 days). She even feeds the young pretty much on her own; they fledge between 9 and 12 days after hatching. Despite such an uninvolved father, the female often raises a 2nd brood if conditions (e.g., weather, food supply) bode well. To be fair, older males appear to be a bit more helpful than first-year males, feeding the brood once they have fledged and thus allowing the female to start a 2nd clutch sooner.
The stunning indigo of the adult male figures prominently in both the scientific and common names of this species. Known in scientific circles as Passerina cyanea, this name means simply “dark blue” (from Greek, kuaneos) “sparrow-like bird” (from Latin, passerina). The precise origin of “bunting” is unknown; but the OED suggests a derivation from the Scandinavian bunting, meaning thick or plump—referring to the plump-ish body.
A male Indigo Bunting on his breeding territory is an enthusiastic singer, often belting out his song all day from a high perch—even in the heat of mid-day, when most other songbirds have taken a break. When we were atlasing for Colorado’s 2nd Breeding Bird Atlas a few years ago, we had no doubt that a male had an established territory along the Arkansas River on the north shore. From late May until August, we first heard, then spotted, this tiny songster serenading from an exposed perch on the power lines or at the top of one of the tallest trees along Country Road 45. A series of bright, whistled notes, one onomatopoetic rendering of his song is “what! what! where! where! see it! see it!”—capturing the frequent repeating of a phrase before moving to the next couplet. This clear, cheery song has earned him the moniker “the blue canary.” Few birds in Colorado rival the striking beauty of the male Indigo Bunting. His brilliant blue plumage and sweet, complex song offer Colorado bird fans a delicious treat for both eye and ear until they head south in August and September.
To read more about this species and to hear his lovely song, visit http://wp.me/P16Ptu-le.