Young bald eagles from Arizona are defying typical migration patterns by heading north during summer and fall, according to a new study. Researchers tracked these birds using satellite transmitters and found they rely on historic stopover sites while facing significant threats. The findings highlight the need for targeted conservation efforts to protect their routes.
A study published in the Journal of Raptor Research reveals that nonbreeding bald eagles (Haliaeetus leucocephalus) from Arizona migrate northward instead of south, challenging conventional expectations for temperate-region birds. Titled "Northward Migrations of Nonbreeding Bald Eagles from Arizona, USA," the research tracked 24 newly fledged eagles and two nonbreeding adults between 2017 and 2023 using satellite transmitters. These birds, which nest in Arizona during winter, enter their nonbreeding season in summer and autumn, prompting journeys deep into the northern U.S. and southern Canada.
The eagles paused at lakes and rivers identified as key stopover sites in a 1980s study, underscoring the enduring importance of these habitats along the Intermountain Flyway. As the birds matured, their migration paths became more refined. Most returned to Arizona in the fall after their hatch year, potentially seeking seasonal food sources like spawning salmon or nesting waterfowl. Lead author Dr. Caroline D. Cappello noted that "northward migratory behavior raises interesting questions about the recent and historical pressures that shape these movement strategies."
One tracked eagle crossed ten U.S. states and four Canadian provinces before settling in northern California, where it appeared ready to breed. Tragically, at four years old, it died from electrocution—a common hazard for large raptors. Cappello explained that this loss "underscored the ongoing risks these birds face," including poisoning from lead and rodenticides, wind turbine collisions, habitat loss, and climate uncertainties. Coauthor Dr. Javan M. Bauder emphasized, "managing and conserving wildlife populations requires that we understand the movement patterns of individuals of all age classes within those populations."
The study suggests southwestern bald eagles are highly exploratory to locate transient food resources. Researchers recommend further investigation into route fidelity to focus conservation on high-use areas and infrastructure modifications, such as safer electrical systems, to enhance survival.