AILSA CHANG, HOST:
Swarms of tricolored blackbirds once blocked out the sun in California. Now the population has plummeted so much that last year the bird became a candidate for the California Endangered Species List. Valley Public Radio's Ezra David Romero reports on efforts to keep the bird from disappearing.
EZRA DAVID ROMERO, BYLINE: West of Fresno, on Steve Shehadey's dairy, there are 7,000 cows and 7,000 tricolored blackbirds.
STEVE SHEHADEY: You can drive out here any time and you'll see colonies of birds pecking at insects, looking for food.
ROMERO: The birds are six inches long with a red spot and white stripe on their shoulders. Shehadey and I meet Samantha Arthur with Audubon California in the middle of one of his fields where the colony of birds recently decided to call home.
SAMANTHA ARTHUR: We are walking right next to a dense patch of mugwort that tricolored blackbirds have selected for a colony site. And then right over this berm here is a field of triticale where they're also nesting on the dairy there.
ROMERO: That's a problem when farmers go to harvest, which can crush thousands of eggs and baby birds. Arthur roams the state looking for nesting colonies. She recorded this group at a farm in Northern California earlier this year.
(SOUNDBITE OF BLACKBIRDS CHIRPING)
ARTHUR: Tricolored blackbirds have experienced an alarming decline in recent years. We've seen from statewide surveys a 44 percent drop from 2011 to 2014.
ROMERO: Audubon California reports there are as few as 150,000 left. In response, the California Fish and Game Commission is considering listing the bird as an endangered species later this year. Arthur blames that decrease on a loss of foraging ground and marshland for nesting.
ARTHUR: Tricolored blackbirds are the last bird on land in North America that nests in big groups.
ROMERO: When the birds nest in grain fields, farmers can apply for a little over $600 per acre reimbursement from the USDA to cover the costs of delaying harvest. But some farmers argue that isn't enough. The birds nest in agricultural areas because there's just not enough natural habitat left in California for them to lay their eggs.
About an hour north of the dairy, field biologist Tara Wertz is studying the tricolored blackbird at the 10,000-acre Merced National Wildlife Refuge.
TARA WERTZ: That call that sounds kind of like a cat, (imitating call) that's the males saying hey, party's on right here.
ROMERO: Wertz is conducting something of an experiment. She planted a plot of grain near a wild area to see what the birds preferred. The birds chose the natural option.
WERTZ: We have really nice, vigorous green plants growing very thick. And right now, this milk thistle patch is very tall and just perfect nesting habitat for the birds.
ROMERO: But since there isn't enough natural habitat left for the tricolored blackbird in California, Wertz says the program providing funds to dairies is essential to saving the species. For NPR News, I'm Ezra David Romero in Fresno. Transcript provided by NPR, Copyright NPR.