Like most elusive marsh birds, American Bitterns prefer to be heard, not seen. But it was just the opposite for photographer Jim Morris last week, when he spied the pinstriped herons on a California rice farm before picking up on their distinctive booming calls.
Morris was driving through a field north of Sacramento, looking to snap ibises reported by a local farmer, when he spotted two short-legged birds strutting down a levee. After stopping the truck, he quietly pulled out his recording equipment and filmed the male as it lurched and gulped for its mate. The intimate encounter lasted for about 15 minutes, after which the pair blended back into the grass.
“This is the best time to see [American Bitterns],” Morris says. “They try to be invisible, but when the rice is just planted and is just a few inches tall, they’re not.”
As the communications manager for the California Rice Commission, Morris has spent 11 years scouting flooded farms in the Central Valley for wildlife. So, when he found the bitterns mid-display, he knew exactly what to expect next. Morris’s video shows the intricate details of the species’ breeding behavior: The male bittern puffs out its esophagus, snaps its beak, and jerks its neck back—all in one pop-and-lock motion. This produces a series of clicks, along with a unique glug glug sound, as if the bird is moving water instead of air through its vocal chords. The call might be bizarre, but it resonates well through dense reeds and grasses, where bitterns typically make their homes.
“A lot of wetland birds have deeper songs and calls,” says Auriel Fournier, a marsh-bird and wetland-ecology expert. “From what I understand, that’s often because those deeper sounds travel better through a very dense environment.” In contrast, a higher, more lyrical whistle from a songbird may get muffled in the thick ranks of plants.
But how does the bittern’s milk-jug effect work? James Chapin, former curator of birds at the American Museum of Natural History, looked into the question way back in 1922. By blowing air through a glass tube to inflate a dead specimen, he was able to take a closer look at the species’ neck and anatomy. Chapin concluded that like other birds, the bittern’s sound originates in its syrinx—the avian equivalent of a larynx. To then manipulate the noise, the male fills its esophagus with air and contracts its neck muscles in an abrupt, undulating motion, resulting in a series of thumping gulps.
The behavior is tougher to witness in the wild, unless you’re rooting around a rice farm like Morris. In the Central Valley, American Bitterns often nest on purposefully flooded fields instead of marshes. This ups the chances of studying them out in the open—an important opportunity, given the level of mystery around the birds.
In fact, bitterns are so secretive, it’s hard to know what exactly is happening with their populations, says Xerónimo Castañeda, conservation project associate for Audubon California’s Working Lands Program. The North American Breeding Bird survey estimates that American Bittern populations have been declining across the United States since the 1960s, likely in part due to habitat loss. That could be the case in California, where 90 percent of wetlands have disappeared under skyscrapers, sidewalks, and tractors.
Thankfully, rice farms have become a suitable stand-in for bitterns and other native wetland birds in the Central Valley. Almost all of the rice for U.S. sushi rolls is grown in the Golden State, says Paul Buttner, environmental manager for the California Rice Commission. The fields also provide crucial supplemental habitat for waterbirds migrating along the Pacific Flyway, he notes.
To these ends, for the past 10 years, Audubon California and the California Rice Commission have been working together on projects like the Water Bird Enhancement Program, which incentivizes rice farmers to prioritize the bird-friendly elements of their lands. This includes keeping fields wet before late-summer harvests and during the end of the winter, when growers traditionally flood the flats to break down leftover stalks. To date, the projects have covered 100,000 acres of farmland in the northern end of the Central Valley.
“The work we do with rice farmers to provide this surrogate wetland habitat is a really neat and cool opportunity to highlight how food production and wildlife conservation can work together to protect species,” Castañeda says.
And it's this farm-to-habitat conservation that also helped bring Morris’ bittern moment to life. The video might seem like a case of fortuitous footage, but the truth is, there’s a decade worth of scene-setting behind it.
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