Lark Bunting

The Lark Bunting (Calamospiza melanocorys) is a medium-sized, highly social songbird of the North American grasslands. Though historically referred to as a "bunting," genetic studies place this species within the American sparrow family (Passerellidae), of which it is the only member in its genus. This species is famous for its extreme sexual dimorphism during the breeding season and its highly nomadic lifestyle. While breeding males boast a stark, jet-black plumage accented with snowy white wing patches, females and non-breeding individuals wear a cryptic, heavily streaked brown plumage. As the state bird of Colorado, it is a classic icon of the undamaged shortgress prairies of the American West.

Identifying Lark Buntings depends heavily on the season and the sex of the bird.

Breeding Males

• Plumage: Entirely velvet-black body with contrasting, large white patches on the wing coverts.
• Bill: Thick, conical, and pale bluish-gray.
• Tail: Black with white tips on the terminal feathers, visible in flight.

Females, Immatures, and Non-breeding Males

• Plumage: Grayish-brown overall, with heavy dark streaking on the back and whitish underparts.
• Wing Patch: Retain a distinct pale buff or whitish wing patch, though it is smaller and less stark than the breeding male's patch.
• Face: Prominent pale stripe over the eye (supercilium) and a dark jaw stripe.

Similar Species

• Bobolink: Breeding male Bobolinks also feature a black-and-white pattern, but they have a yellowish-buff patch on the back of the head and a white back, lacking the prominent white wing patch of the Lark Bunting.
• Sparrows (various): Female and winter Lark Buntings resemble large sparrows but can be distinguished by their disproportionately large, bluish-gray bills and the presence of the buffy wing patch.

Lark Buntings are birds of wide-open spaces, requiring native shortgrass prairies, sagebrush shrublands, plains, and sometimes agricultural fields or pastures. Breeding populations are highly nomadic, often shifting their nesting locations from year to year to follow areas with recent rainfall, which triggers abundant insect hatches.

Range and Migration

• Breeding Range: Primarily the Great Plains of North America, extending from southern Alberta and Saskatchewan down through Montana, Wyoming, Colorado, and the western Dakotas.
• Wintering Range: They migrate in large flocks to the desert grasslands of the southwestern United States (Texas, New Mexico, Arizona) and northern to central Mexico.
• Migration Behavior: Lark Buntings are highly gregarious during migration and winter, often forming massive, rolling flocks that forage together across desert flats.

Breeding and Courtship

During the breeding season, males perform spectacular aerial courtship displays. A male will fly upward at a steep angle to about 10-30 feet in the air, then glide or flutter slowly back to the ground while pouring out a complex, melodic song.

Vocalizations

• Song: A rich, varied series of sweet whistles, harsh chattering notes, and clear trills.
• Call: A distinct, rising, two-syllabled ch-up or hoo-ee flight call, which is highly useful for identifying flying flocks.

Feeding and Diet

Lark Buntings forage entirely on the ground, walking or running (rather than hopping) in search of food. During the summer, their diet consists almost entirely of insects, with grasshoppers being their primary prey during the nesting season. In winter, they transition to a diet primarily composed of seeds from grasses, weeds, and agricultural grains.

Nesting

Nests are built on the ground, typically placed in a small depression scraped into the earth. The nest is carefully concealed under overhanging vegetation, such as a clump of grass, a sagebrush, or a yucca plant, to shield the eggs and chicks from the harsh prairie sun and predators.