SAN FRANCISCO (AP) — A conservation group is planting more than 30,000 milkweed plants throughout California in the hope of giving Western monarch butterflies new places to breed.

The San Francisco Chronicle reports Monday that the River Partners group has joined with others and the California Department of Fish and Wildlife for the plantings along the Sacramento, Feather and Kern rivers.

The plants are seen as critical because the orange-and-black butterflies lay their eggs on them. Their caterpillars also eat them.

Earlier this year, researchers said an annual winter count recorded fewer than 2,000 of the butterflies. That's a massive decline.