After more than a year, Steven Prager had all but given up on monitoring for local Motus pings. Audubon’s Appleton-Whittell Research Ranch in Arizona, where Prager is the director, installed its radio telemetry tower in March 2022. At the start, Prager checked the ranch’s data log daily for any indication that a bird tagged with a radio transmitter had passed nearby. But months of nothing had dampened his initial eagerness. “I hadn’t been checking it frequently at all,” he says. Then, one day last month, he got a text from a friend and fellow researcher tracking a Western Yellow-billed Cuckoo wearing a transmitter. The bird, his friend said, was on the move and may have come through the ranch.
Indeed, when Prager checked the database, a ping had popped up on the Appleton-Whittell Motus tower. The cuckoo had spent about 15 minutes within range of the wildlife sanctuary’s antenna on August 10. “It was super exciting for me,” Prager says. The conservationist spent much of his early career monitoring Yellow-billed Cuckoos in their western range, where, thanks in part to Audubon's efforts, they’ve been listed as federally threatened since 2014. Though the birds are larger in size with long showy tails and yellow bills, they’re rarely seen in the dense woodland habitats they prefer. “I was sure that the first bird that was gonna fly by [the tower] would be like a House Finch or a White-winged Dove—just something common and expected,” Prager says. “Instead, it’s this federally threatened bird that I’ve been thinking and talking about at Audubon for the last dozen years, which just seems like a crazy stroke of luck.”
He’s not the only one excited about the cuckoo's migratory movements. Radio telemetry data from Motus towers in California, Arizona, and Mexico indicates that the bird has passed through at least six different protected areas on its southward migration. This includes the Audubon Kern River Preserve in California where the cuckoo was first banded and outfitted with its transmitter earlier this summer by staff from the Southern Sierra Research Station (SSRS), a nonprofit conservation group. The team also gave the cuckoo its delicious name: Hummus. Another cuckoo banded by SSRS at Kern River was dubbed Baba Ganoush to keep with this year’s dip theme. (The crew uses a new name theme each year to allow for funny and memorable monikers for each tagged bird.) SSRS researchers have been eagerly following both birds’ activity since their initial capture. Though Baba Ganoush has stuck around Kern River, not yet on its own migration path, Hummus has been serving up a feast of valuable data. The rare bird’s journey offers insight into how conservationists can better protect the species moving forward and supports the case for land preservation as a mode of wildlife conservation.
“It definitely generates excitement when we find a new detection,” says Patrick Lorch, a senior biologist at SSRS who leads the station’s Motus projects. Each ping adds to science’s understanding of Western Yellow-billed Cuckoo migrations habits, he notes, which is particularly valuable in a region where such information has historically been scarce. Nick Beauregard, another SSRS biologist and the friend who texted Prager about Hummus, agrees. “It makes me feel like my work as a conservationist is paying off,” Beauregard says. “It’s just a really awesome demonstration of this new technique for monitoring migration and bird movements.”
Hummus is only one bird, but its movements are likely representative of others of its species, adds Mary Whitfield, the research director at SSRS. The more data there is demonstrating where Western Yellow-billed Cuckoos spend time and what their migration routes look like, the easier it might be to help the imperiled birds in the future by strategically setting aside habitat, she says.
More broadly, Hummus’s journey confirms the value of preserved lands for migrating birds and other wildlife. “The worth of these protected areas is really to provide for these birds,” says Adriaan Dokter, a migration ecologist at the Cornell Lab of Ornithology. Birds on the move are particularly vulnerable and need “good areas to fuel and to stop over, to make these extraordinary long migrations,” he adds. For migratory species, “it’s very important that there’s a broad network of suitable sites and protected areas that they can make use of.”
Yellow-billed Cuckoos are considered a riparian species in their western range, closely associated with water. In the Southwest, they rely on the broadleaf forests that generally only grow along streams, rivers, and lakes. The trees provide shelter and house a supply of juicy insects that support cuckoos’ quick growth from egg to fledgling, as well their energy-intensive, nocturnal migration flights. But riparian habitat has sharply declined across the Southwest over the past century and a half due largely to development, livestock grazing, and agriculture, with some estimates listing 90 percent of water-adjacent habitat in the region as degraded or destroyed. Extensive drought and overallocation of the Colorado River have only made matters worse.
Thankfully for Hummus, the patchwork of conserved, restored, and undeveloped habitat across the Southwest seems to have paid off so far, supporting the bird well enough to fly more than 900 miles from its Central California breeding site at Kern River to the western coast of Mexico over 9 days. Yet Hummus still has a long way to go. Yellow-billed Cuckoos overwinter in the Dry Chaco ecoregion, which encompasses parts of Brazil, Paraguay, Bolivia, and Argentina. From Mexico to that final destination is thousands more miles. In this next leg of migration, Hummus will likely be more difficult to keep tabs on, says Lorch, as Motus towers are few and far between in South America.
Still, Prager says he’ll be checking the Motus database every day to see if the bird pops up elsewhere throughout the season. And after the pleasant surprise of Hummus's arrival, he plans once again to start keeping a close eye on Appleton-Whittell’s own tower data, watching for whatever treats migration might deliver next.