Cowbird trap

An empty cowbird trap is located at the edge of English Creek in Chino Hills.

A large trap for small birds that prey on an endangered species may not be doing the work it was meant to do along the English Creek that traverses three city facilities on Peyton Drive near Eucalyptus Avenue.

The trap was empty this past week when it should have contained live “bait” cowbirds to lure other cowbirds away from the least Bell’s vireo songbird located in the habitat.

The City of Chino Hills created the riparian habitat in 2015 after the widening of Peyton Drive impacted nesting grounds of the songbird, as mandated by the California Department of Fish and Wildlife.

The trap was installed by the Santa Ana Watershed Association (SAWA) and remains there between March and August.

Although the time period has passed that the City has been mandated to retain the trap, SAWA requested that it continue placing the cage near the habitat to further protect the least Bell’s vireo.

The wings of the cowbirds placed in the trap are clipped.

Melody Aimar, lead biologist with SAWA, said Thursday she will dispatch a biologist to check the empty cage to find out if vandalism occurred or if people may have released the bait birds thinking they were doing the right thing.

She said the cowbirds won’t survive if released because their wings are clipped.

Ms. Aimar, who is also manager of SAWA’s wildlife habitat management service, said the least Bell’s vireo is not doing well in Chino Hills because of the cowbirds. 

The cowbird is referred to by biologists as a “brood parasite” because instead of making its own nest, it lays eggs in other nests forcing a “foster” bird to raise its chicks.

The least Bell’s vireo often leaves the nest when this occurs, and her eggs perish.

Ms. Aimar said one cowbird can lay at least 30 eggs per season.

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