What is A Cowbird's Habitat?
Cowbirds received their name in the early 19th century when they were seen feasting on insects stirred up by herds of American bison populating the Great Plains. Their habitat range, especially that of the brown-headed cowbird (Molothrus ater), has since expanded greatly. They're now found over a vast range that includes southern Alaska and Canada, the lower 48 states and southern Mexico.
Cowbirds are brooding parasites, laying their eggs in the nests of other birds. Quite large, cowbird chicks may get a disproportionate share of food. Even so, the cowbird fledgling survival rate is only 28 percent
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Historical Habitat
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The cowbird's habitat has expanded greatly since the passing of the American bison. They first spread to the eastern half of the United States during its 19th century deforestation. When the western US and lower Canada were developed, beginning in the early 20th century, cowbirds became common there as well.
They benefited both from the new winter food supply of grain left behind in harvested fields and from forest destruction opening up the habitats of other bird species. The latter gave them access to more nests in which to lay their eggs.
Breeding Habitats
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Because they don't build their own nests, cowbirds have a nearly unlimited selection of breeding habitats. They may breed in their feeding areas and fly long distances to entirely different habitats before depositing their eggs in established nests. The National Zoo reports that some cowbirds have been tracked flying as much as 4.3 miles (7 km) between their feeding/breeding grounds and their egg- laying habitats.
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Feeding Habitats
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Cowbirds thrive in livestock-producing areas, where both grain and insects are plentiful. They love feedlots, barnyards with silos and grain-packing plants. They eat seeds and soft fruit like berries, grapes or cherries.
They also eat caterpillars, snails, crickets, grasshoppers, beetles and spiders. They've adapted to survive on what they can find in garbage dumps around parks and campgrounds, and to eating from bird feeders.
Egg- Laying Habitats
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According to the Audubon Society, cowbirds prefer cup-shaped nests found in field shrubs and at the edges of forests. The female cowbirds scan for promising nests from above, often seeking trees at the edges of overgrown grasslands. The birds frequent habitats where deforestation creates stands of trees interspersed with low brush or open grassy areas.
Female cowbirds indiscriminately choose other birds to raise their young. Indigo buntings, northern cardinals, grackles, red-winged blackbirds and grackles are among the hundreds of species that have raised cowbird chicks.
Cowbirds tend to avoid unbroken tracts of forest, possibly because the density of the trees makes it difficult for them to find suitable nests.
Controlling Cowbird Habitat
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If you're a landowner concerned about the effect cowbird parasitism has on the songbirds in your area, make your property less appealing to them. Naturalize fields adjacent to forests so their grasses grow to full height.
Keep roadside vegetation at least 6 inches high to keep them from feeding in it. Plant bare ground with tall grasses. All of these methods will prevent cowbirds from feeding on your land.
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References
Resources
- Photo Credit Gala Web Design http://commons.wikimedia.org/wiki/File:Eastern_Phoebe-nest-Brown-headed-Cowbird-egg.jpg; http://commons.wikimedia.org/wiki/File:Brown-Headed_Cowbird.jpg
