Brown-headed cowbird male and female, 2013. Lisette Lebaillif. Image courtesy of Wikimedia Commons.

A tiny Pacific Wilson’s Warbler parent feeding much larger Brown-Headed Cowbird fledgling, 2008. Alan Vernon. Image courtesy of Wikimedia Commons.

brown-headed cowbird

Molothrus ater

Identification: 
The male is a shiny black bird with brown head and thick beak; overall it’s larger than a sparrow but smaller than a robin.  The female is brownish overall with faint streaks; she’s very hard to distinguish from similar birds like the female House Finch. 

Behavior:
This species employs a reproductive strategy called “brood parasitism,” where the female builds no nest but instead deposits eggs in other bird nests where the hapless hosts get stuck babysitting and chick rearing, often at the expense of their own offspring.  In 2016 in the SBG habitat an adult Red-Eyed Vireo was spotted feeding a much larger cowbird chick.  Since they devote no energy to nesting or feeding babies, female cowbirds may lay several dozen eggs in a season.

What brings it to the SBG?
Food, cover, other birds’ nests.  These birds prefer open grassland and thrive near human settlement and domesticated livestock.  It’s no surprise, then, that they have been observed drinking from the horses’ water supply just across from the SBG habitat.

When can I see it?
Year-round.