Brown-headed cowbird

Female cowbirds lay eggs in the nests of more than 200 other species and leave the hosts to raise their young. Cowbird chicks often hatch first and grow faster than their nest-mates.

Cowbirds once followed bison herds across the plains, feeding on insects stirred up by the animals — a life that made staying to tend a nest impossible. As forests were cleared, they spread east and now parasitise many songbirds that had little defence.

Nest — None; eggs laid in other birds' nests
Eggs — A female may lay dozens in a season
Incubation — About 10 to 12 days, by the host
Chicks — Raised by the host parents
Lifespan — Several years

• Cowbirds and their eggs are protected under federal law like other native birds.
• A songbird feeding a much larger chick is raising a cowbird.

• Cowbirds are evil. They are simply following a strategy that evolved with bison herds.

• Red-winged blackbird
• Common grackle