On the southern tip of Vancouver Island, where the Strait of Juan de Fuca stretches eighteen kilometers wide, turkey vultures gather in spiraling towers of air before taking flight across one of North America's most challenging water crossings. For twenty-five years, researchers at Rocky Point Bird Observatory have been watching these congregations—called "kettles" for their swirling, kettle-shaped formations—and what they've discovered is a remarkable story of resilience and adaptation playing out in the skies above British Columbia.
Turkey vultures are not typically cast as climate heroes. These large, dark raptors are often overlooked or misunderstood, yet they perform one of nature's most essential services: removing carrion from the landscape. A new study published in the Journal of Raptor Research reveals that western North American turkey vulture populations have surged by nearly 300 percent over the past quarter-century, and the birds are departing on their southern migration roughly four days later than they did in the late 1990s. Both trends may be linked to our warming climate, though researchers emphasize more investigation is needed to fully understand the connection.
Dr. Daniel Dönnecke, a longtime volunteer at Rocky Point Bird Observatory and lead author of the study, noticed something unexpected in the data. Between 1999 and 2023, the annual maximum number of turkey vultures observed in kettles climbed steeply. The counting method itself—tracking vultures in organized groups rather than as individuals—proved surprisingly effective. "Our study indicates that counting raptors in kettles can offer information on population trends, likely with less effort than at hawk watches," Dönnecke explains, noting that traditional hawk watches require counting individual birds one by one as they pass through.
Turkey vultures are facultative migrants, meaning some travel thousands of kilometers south to Venezuela each winter while others remain behind. The species has evolved sophisticated adaptations for long-distance travel, riding thermals and updrafts along ridges and landscape features that funnel them efficiently toward their destinations. But before they can cross major water barriers like the Strait of Juan de Fuca, they must gather and wait for the right atmospheric conditions—those moments when Dönnecke and his team documented their remarkable numbers.
The four-day shift in migration timing is particularly intriguing. As global temperatures rise, springs arrive earlier, food sources emerge sooner, and animals across the globe are adjusting their life cycles accordingly. For vultures, the delayed departure may suggest they're finding adequate sustenance longer into the season, or that warming temperatures are changing the availability of resources. "Before our study, there was little recent information about western populations of turkey vultures," Dönnecke says. "To make decisions about conservation efforts, it's important to have up-to-date information about whether the population is increasing, decreasing or stable."
The increase in turkey vultures has also been documented through citizen science platforms like eBird and the Breeding Bird Survey, suggesting that Rocky Point's findings reflect a genuine regional trend rather than a localized phenomenon. Dönnecke and his co-author Dr. Don Kramer hope this research will spark collaboration between different monitoring sites, pooling data to track how various species are shifting their migration timing in response to climate change. Perhaps most importantly, they hope the public will begin to see these adaptable vultures not as ugly scavengers, but as intelligent indicators of how our changing world affects the animals we share it with.