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Also see Nest ID Matrix (contents) and Egg ID Matrix (color, spots, etc.)
Select bird name (alphabetical):
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LEFT: Photo by Bet Zimmerman of cowbird egg in Black-capped Chickadee nest in a Gilwood box. This nest was abandoned.
ABOVE: Photo of Titmouse nest with cowbird egg by Jay Brindo of Ohio. |
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![]() Cowbirds seem to prefer open cup nests, and the nests of other birds that also lay speckled eggs. |
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Photo on left: Cowbird nestling (same as photo directly above). Two days later when I checked this box, the nestling was dead. I assume it was abandoned. Photo by Bet Zimmerman. | ||
![]() Photo below by Jay Brindo of Ohio, probably one cowbird egg (the larger one) in a House Sparrow nest. |
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![]() Since cowbird young tend to hatch earlier, their eyes open soon, and their mouths are bigger than the host’s young, the rest of the nestlings often die. Some nestbox monitors remove cowbird eggs when they are found. Technically, in most states this is illegal, as cowbirds are native birds. In some states (e.g., TX) where cowbirds threaten certain declining bird species (e.g., Kirtland’s Warbler) permission may be obtained to remove cowbird eggs and to trap adults. |
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Cowbirds are short distance migrants. They often flock and roost with Red-Winged Blackbirds, Common Grackles, European Starlings and American Robins, making up 1-3% of those mixed flocks. (BNA.) |
MORE INFORMATION:
- Cowbird Biology
- Egg ID matrix
- Egg size comparison
- Cowbird egg (photo) in: Eastern Bluebird Nest | Sparrow nest
The student of Nature wonders the more and is astonished the less, the more conversant he becomes with her operations; but of all the perennial miracles she offers to his inspection, perhaps the most worthy of admiration is the development of a plant or of an animal from its embryo.
-Thomas Henry Huxley, British biologist and educator. Reflection #54, Aphorisms and Reflections, selected by Henrietta A. Huxley, Macmillan, 1907.