BIRD OF THE WEEK: December 1, 2017
SCIENTIFIC NAME: Calamospiza melanocorys
POPULATION: 10 million
HABITAT: Breeds on shortgrass prairie or sagebrush plain with grassy understory. Uses wide variety of open habitats during migration and in winter.
"Our Troubadour of the Plains is gentle of manner and pleasingly sociable among his fellows. He lives a beautiful family and community life. Amiability is a characteristic trait."
— Ornithologist Frank W. Langdon, 1933
The Lark Bunting is a gregarious species, found in large flocks that sometimes number in the thousands during migration and in the winter. The birds even nest in loosely-knit colonies on the dry western grasslands where they breed, alongside species such as Horned Lark or Mountain Plover. This "bunting" is actually a member of the sparrow family, more closely related to Chestnut-collared Longspur than to Painted Bunting.
A male Lark Bunting in breeding plumage is a striking sight, with its jet black body and contrasting large white wing patches. Its appearance has given rise to other folk names such as white-winged blackbird and white-winged bunting. The male is the only sparrow that completely changes in appearance from breeding season to winter, when it molts into a streaky brown plumage that resembles a female's or juvenile's.
The male's musical song, a series of whistles and trills, is given while perched and during its elaborate flight display.
Lark Buntings breed from Canada south through northern New Mexico and Texas; they winter from the southern Great Plains to the Chihuahuan grasslands of central Mexico. Their numbers may fluctuate greatly from year to year on their breeding grounds, depending on local drought conditions.
Like Spague's Pipit, male Lark Buntings use flight displays to establish and maintain territory. The male begins his display by ascending 20 to 30 feet on stiff wingbeats, then floating back to the ground on outstretched wings, singing all the while. Males perform two different flight songs – one given from a perch or flight, the second always given in flight, most often with other males performing the same song. As many as five or six males may display in concert.
Although chiefly monogamous, Lark Buntings may resort to polygyny (one male with several mates) in high-density areas. The female builds a cup-shaped nest in a depression scraped under a shrub. Nests are oriented to take advantage of morning sun, cooling winds, and protection from mid- to late-day sun.
After fledging, immature Lark Buntings form flocks and remain on the breeding grounds after adults have already migrated.
Lark Buntings feed mainly on insects, particularly grasshoppers, during their breeding season, flushing prey from the grass as they run or hop. They also make short flights to hawk insects from the air. During migration and in winter, they gather in large flocks to glean for seeds, grain, and even cactus fruits.
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Although the Lark Bunting is still a common across most of its range, it is classified as a "Common Bird in Steep Decline" by Partners in Flight, with an 86 percent population loss noted from 1970-2014. In general, grassland birds in North America, including Northern Bobwhite and Bobolink, have experienced large population declines in the past 40 years.
Since grasshoppers make up a significant portion of the Lark Bunting's diet, pesticides are thought to have played a role in their decline, particularly on their breeding grounds. Large numbers of these birds also drown in water tanks used for livestock, particularly in drought years.
ABC works with partners across the Americas, such as the Rio Grande Joint Venture and Pronatura Noreste, to preserve and restore the habitats that the Lark Bunting and other threatened grassland species — such as Long-billed Curlew and Baird's Sparrow — require as wintering habitat.
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