Grassland Bird Diversity in Sacramento County

Across an expanse of open grassland in Sacramento County, an eight-foot, stream cut bank holds dozens of mud-domed bird nests, where tiny heads peeked out before a colony of cliff swallows took flight. Cliff swallows are small migratory birds that arrive in the Central Valley each spring to breed, and while they now commonly nest on bridges and freeway overpasses, finding their nests built in a natural setting is a striking and special sight, particularly in California’s Central Valley.

The discovery came during a field visit for a study led by Andrew “Andy” Engilis, Jr., curator of the UC Davis Museum of Wildlife and Fish Biology, and student researcher Zane Pickus, a senior majoring in wildlife, fish and conservation biology who is documenting the diversity of grassland birds across an 11,000-acre ranch protected by a conservation easement that prevents development. The property’s landscape of grasslands, blue oak woodlands and vernal pools serve as critical habitat for the region’s grassland birds, some of which are experiencing population declines. This project is part of the museum’s Sacramento Valley Avian Research Program.

“We are hoping to gain a better understanding of bird breeding activity and by doing so, spark an interest in this dwindling habitat, and ultimately towards its protection,” Engilis said.   

Audio tools in the field

The site is a working cattle ranch and home to several special-status species, including grasshopper sparrow, tricolored blackbird, ruddy horned lark and burrowing owl. The research is focused on understanding how grassland birds are distributed across the landscape and how their activity changes through the breeding season. To do that, Pickus, along with fellow student Julian Johnson, installed 14 automated recording units that will capture recordings of bird sounds across the property from now through July. The data will help track where species occur, how abundant they are and when they reach peak singing activity.

The rugged, weatherproof devices are programmed through a smartphone app. Pickus and Johnson have attached some to high branches of the California blue oak trees on the property, while others are mounted on stakes across open grass and vernal pools. Pickus said the recorders are programmed to sample bird activity at key times of day, including an hour before sunrise to an hour after, and again in the evening around sunset, when birds are most active and vocal.

“We also have them set to take a five-minute recording every hour, and that will give us an idea of the variation along different times of day and night to determine when they’re most vocal,” Pickus said.


The devices are recording approximately five hours of audio each day. Pickus will later review the audio files using BirdNET, a machine-learning tool developed by Cornell University that identifies species from sound by turning recordings into a spectrogram, a picture of sound that shows time, pitch and loudness.

“BirdNET shows a visual representation of the sound, and it looks at that and sees if it recognizes any of the shapes of the sounds and will compare it to the millions of examples that it has to identify species,” he said. “Western meadowlark and grasshopper sparrows have really distinct vocalizations that the software should be able to recognize with high confidence.”

Informing conservation efforts 

Pickus and Johnson are also conducting visual surveys on the ranch every other week. During a recent visit, the research team spotted 44 species, including Lewis’s woodpeckers, western kingbirds, Swainson’s hawks, turkey vultures and a lesser nighthawk, and they heard mockingbirds singing. 

“Sometimes mockingbirds will imitate non-bird sounds; I remember in junior high there was one at our school that would imitate the school bell very accurately,” Pickus explained.

In a small marsh, with the Sierra Nevada mountains as a backdrop, the researchers also pointed out mallards, a great blue heron, two American wigeons, double-crested cormorant, white-crowned sparrows and a pair of killdeer. They were happy to see a few grasshopper sparrows and a possible breeding colony of tricolored blackbirds, a threatened species because the grassland habitat that they forage in is disappearing.

“The tricolored blackbird is in a dramatic decline,” Engilis said. “A lot of its habitat has been degraded in California. The conversion of these grasslands to vineyards, through urbanization and solar panel fields, those are big threats to this region’s grassland birds.”

The data will also help guide future conservation efforts and ranching decisions by showing how birds are using this stretch of grassland and what conditions support them. Engilis said the project also gives student researchers hands-on field experience, building skills in data collection and acoustic monitoring that help prepare them for future careers in conservation and ecology.

“Zane and Julian know their birds. What they’re learning is technique and methodology and how to conduct a study in the real world,” Engilis said. “When they’re done with this project, they’re going to have had a level of experience that they can translate into graduate work or into their professions.” 

Pickus will spend the fall analyzing hours of audio recordings, working toward a more complete snapshot of bird diversity in this part of the state. He said the workload doesn’t feel daunting because it just means more time spent doing what he already enjoys – listening to birds.

“Andy said something to me, he said, ‘Make sure you don’t take on too many birding tasks,’ and I’m like, ‘That’s what I'll be doing with my free time anyway,’” Pickus said. “I really love it.”

This project is funded in part from a museum donation by UC Davis alum Punit Lalbhai, who worked in these grasslands as an undergrad interning with the museum in 2004. In addition, the research project is supported by the Yolo Bird Alliance, Selma Herr Fund for Ornithological Research, Central Valley Bird Club and a Provost’s Undergraduate Fellowship.