Brown-headed Cowbird

Steve Forman photographed this brown-headed cowbird at Breakneck Hill Conservation Land in Southborough.

Steve Forman photographed these brown-headed cowbirds at Breakneck Hill Conservation Land in Southborough.

Steve Forman photographed a brown-headed cowbird, a European starling, a red-winged blackbird, and a song sparrow at Breakneck Hill Conservation Land in Southborough.

Steve Forman photographed a brown-headed cowbird, an eastern kingbird, a northern flicker, and a scorpionfly at Breakneck Hill Conservation Land in Southborough.

Steve Forman photographed brown-headed cowbirds, an eastern kingbird, a red-winged blackbird, and a yellow warbler at Breakneck Hill Conservation Land in Southborough.

Dan Trippe photographed a brown-headed cowbird and a northern flicker at Assabet River National Wildlife Refuge in Sudbury.

Steve Forman photographed a brown-headed cowbird, a house finch, a northern flicker, and a northern mockingbird at Breakneck Hill Conservation Land in Southborough.

Steve Forman photographed a brown-headed cowbird and European starlings at Breakneck Hill Conservation Land in Southborough.

Steve Forman photographed an American robin, a brown-headed cowbird, a northern cardinal, and a red-winged blackbird at Breakneck Hill Conservation Land in Southborough.

Eileen Samberg photographed this yellow warbler feeding a brown-headed cowbird fledgling at Upton State Forest. Brown-headed cowbirds are known as "brood parasites;" the female will lay eggs in other birds...