Illustration © David Allen Sibley.
Learn more about these drawings.
Text © Kenn Kaufman, adapted from
Lives of North American Birds
Photo: Rob & Ann Simpson/Vireo
Molothrus ater
Conservation status | Undoubtedly far more abundant and widespread today than it was originally, and having a negative impact on other species. Surveys suggest slight declines in total numbers in recent decades. |
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Family | Blackbirds and Orioles |
Habitat | Farms, fields, prairies, wood edges, river groves. Favors open or semi-open country at all seasons. In winter often concentrates in farmland, pastures, or cattle feedlots, where foraging is easy. More widespread in breeding season, in grassland, brushy country, forest edges, even desert, but tends to avoid dense unbroken forest. |
Forages mostly by walking on the ground. Often associates with cattle or horses in pastures, catching the insects flushed from the grass by the grazing animals. Originally, was closely associated with bison herds on the Great Plains.
Whitish with brown and gray spots concentrated at larger end. Female may lay nearly one egg per day for several weeks, up to 40 in a season, exceptionally 70 or more. Female often removes an egg from "host" nest before laying one of her own. Known to have laid eggs in nests of over 220 species of birds, and over 140 of those are known to have raised young cowbirds. Young: Fed by "host" parents. Develop rapidly, and leave nest usually after 10-11 days.
Fed by "host" parents. Develop rapidly, and leave nest usually after 10-11 days.
Mostly seeds and insects. Seeds (including those of grasses, weeds, and waste grain) make up about half of diet in summer and more than 90% in winter. Rest of diet is mostly insects, especially grasshoppers, beetles, and caterpillars, plus many others, also spiders and millipedes.
A brood parasite, its eggs and young being cared for by other bird species. In breeding season, male displays by fluffing up body feathers, partly spreading wings and tail, and bowing deeply while singing. Groups of males sometimes perch together, singing and displaying. Nest: No nest built; eggs laid in nests of other birds.
New research explains how these brood parasites—who are raised by other species—still manage to become cowbirds.
These tales and pics from the nest will fill you with wonder and dread.
Robins can identify a parasitic cowbird egg, even when it’s 3-D printed to perfection.
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