Lark Bunting Life History

Habitat

Habitat Grasslands

Lark Buntings are endemic to the grasslands and shrubsteppe of North America—they occur nowhere else. When breeding, they are most likely to be found in large areas of native grassland vegetation, especially wheatgrass, blue grama grass, needle-and-thread grass, and big sagebrush. Lark Buntings live among many species of prairie vegetation, including red triple-awn grass, four-winged saltbush, cottonthorn hornbush, and green-plumed rabbitbrush, all plants in which the birds may nest. Lark Buntings avoid bare ground when nesting (Horned Larks are often found there), preferring shortgrass and taller habitats. They usually nest at the base of a small shrub or cactus, so pure grassland is usually not suitable for breeding habitat. Heavily grazed shortgrass habitats, prairie dog towns, and recently burned fields are not generally used. Wintering and migrating Lark Buntings usually occur in flocks, sometimes with other sparrows, in many types of open habitats, including dry lake beds (playas) at times. Across large areas of their wintering range, abundant natural food is available chiefly where erratic summer rains have fallen. This unpredictability means that Lark Buntings are nomadic during winter, and they frequently show up in human-modified habitats such as cattle feedlots and weedy roadside edges.

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Food

Food Insects

Like other sparrows, Lark Buntings feed on seeds, invertebrates, and some fruits. They likely eat more insects than seeds from spring through autumn: studies in Colorado indicate that about two-thirds of the summer diet is composed of invertebrates. Young are fed mostly insects. Foraging Lark Buntings take seeds while feeding on the ground or strip seeds from grasses and other plants, much in the manner of other sparrows. In pursuit of insects, Lark Buntings are agile and versatile predators, stalking, then chasing them down on foot, pursuing them in flight (females more so than males), and gleaning them from vegetation. One study found that females foraging on the ground moved more quickly than males. Their diet includes seeds of many grasses and forbs, cactus fruit, grains, and leaves, as well as spiders, ants, grasshoppers, flies, beetles, bees, wasps, caterpillars, moths, leafhoppers, and many other invertebrates.

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Nesting

Nest Placement

Nest Ground

The female selects the site for the nest, normally a small depression at the base of a shrub, cactus, or large grass clump that will provide cover and shade. She indicates her preference by scraping the site with her feet. Nests are built on the ground by both sexes.

Nest Description

The nest is a loose cup formed of grass stalks, fine roots, leaves, and stems, lined with fine-blade grasses or hair. The nest’s upper rim is even with surrounding ground or just above it. Nests measure about 3.7 inches across, with the interior of the cup 3 inches across and 1.5 inches deep; the height of the nest varies from about 1.5 to 3 inches.

Nesting Facts
Clutch Size:2-5 eggs
Number of Broods:1-2 broods
Egg Length:0.8-1.0 in (2-2.5 cm)
Egg Width:0.6-0.7 in (1.5-1.8 cm)
Incubation Period:10-12 days
Nestling Period:7-9 days
Egg Description:

Unmarked light blue.

Condition at Hatching:

Helpless with sparse gray down.

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Behavior

Behavior Ground Forager

Males sing in flight or from a perch in a taller shrub, fence, or utility wire. Singing males are most evident in flight: they ascend rapidly, then glide earthward, with most of the song given as they slowly descend. Males arrive on the breeding grounds earlier than females and begin to establish territories where suitable nesting sites (shade-providing plants) are plentiful. At this time, before the arrival of the females, males frequently deliver a flight-song containing more pauses and harsh notes than the song they give later in the season. This different song seems to indicate aggression toward other males, as the males establish individual territories. Males that clash early in the nesting season also communicate aggression by flicking their wings, ruffling the feathers, or contorting the body. Because the birds’ territories are relatively small and thus close together, some observers have assumed that Lark Buntings are colonial nesters that don’t hold individual territories, but this is not the case. Females also show aggression toward other females that enter their territory, and in a few cases, observers have seen Lark Buntings chase sparrows that approached the nest too closely. Once young hatch, the parents forage away from the territory. After breeding, Lark Buntings gather into flocks that migrate, both diurnally and nocturnally, southward toward wintering areas. Most are observed in open lowland areas, but they have been seen at elevations in the Rockies as high as 12,900 feet during migration.

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Conservation

Conservation Common Bird in Steep Decline

Lark Buntings are still fairly common, but their numbers have fallen by an estimated 86% since 1970, according to Partners in Flight. They are designated as a Common Bird in Steep Decline, with an estimated global breeding population of 10 million and a Continental Concern Score of 12 out of 20. If current rates of decline continue, the species will lose another half of its population by 2033. Extensive habitat changes to North America’s prairies and shrubsteppe (breeding habitat) and to desert grasslands (wintering habitat) may be responsible for Lark Bunting declines. Lark Buntings can nest successfully in altered habitats, but at lower densities than in intact grassland or sagebrush. Lark Buntings have been found to increase in numbers in lands planted back to native grasses under the Conservation Reserve Program, although the species’ nomadic behavior makes it difficult to precisely evaluate the effect of the program. Lark Buntings may be affected by pesticides used on agricultural fields. Lark Buntings and other grassland birds drink water from stock tanks, but may fall in and drown (one 1979 report found remains of 25 Lark Buntings in a single tank).

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Backyard Tips

Few backyards have enough open area to attract Lark Buntings regularly, but migrants do occasionally appear in backyards along with other sparrows. Within the species’ range, a water feature, a brush pile, an open sandy area with some native grasses, and offerings of various seeds on the ground might attract a Lark Bunting during migration.

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Credits

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sauer, J. R., J. E. Hines, J. E. Fallon, K. L. Pardieck, Jr. Ziolkowski, D. J. and W. A. Link. The North American Breeding Bird Survey, results and analysis 1966-2013 (Version 1.30.15). USGS Patuxtent Wildlife Research Center (2014b). Available from http://www.mbr-pwrc.usgs.gov/bbs/.

Shane, Thomas G. (2000). Lark Bunting (Calamospiza melanocorys), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Sibley, D. A. (2014). The Sibley guide to birds, second edition. Alfred A. Knopf, New York, USA.

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