Birds of the same species do not always stick together, contrary to the well-known saying. A new study published in the Journal of Raptor Research reveals unusual migration routes of bald eagles (Haliaeetus leucocephalus) from Arizona. Unlike most migratory birds in temperate zones, these eagles travel north rather than south. The article also describes a case where one of the birds left Arizona and settled in California, challenging previous assumptions about how often these birds emigrate from their native population.

Migration Patterns of Arizona Eagles

Researchers concluded that southwestern bald eagles are inclined to explore new territories, likely in search of temporary food sources. As climate and landscapes continue to change, such studies become crucial for developing strategies to protect and preserve key migration corridors for vulnerable species.

From 2017 to 2023, a team of scientists from Arizona used satellite transmitters to track the movements of 24 young and two immature adult bald eagles, studying their routes both within the state and beyond. While nesting eagles in Arizona are believed to stay near their territories for most of the year, much less is known about the behavior of young birds. Comparing movement patterns and survival rates of juveniles and adults provides a more complete picture of the species’ status and the processes shaping the population.

Unusual Routes and Returning Home

Scientists tracked individual eagles as long as the transmitters worked—sometimes up to four years during the seven-year study period. It is generally believed that North American migratory birds head south during their immature season to find milder climates and reliable food sources. However, Arizona’s bald eagles begin nesting in winter, so their immature season falls in summer and autumn.

Lead author Dr. Caroline D. Cappello notes that this northward migration raises interesting questions about recent and historical factors shaping such movement strategies. The tracked eagles stopped at the same lakes and rivers that were identified as important stopover sites for the species back in the 1980s. This confirms that these locations remain key gathering points for several generations of birds.

The Role of Age and Seasonal Resources

The study showed that eagles of different ages migrated to the northern United States and southern Canada. Co-author Dr. Javan M. Bauder emphasizes that understanding the movements of individuals across all age classes is essential for effective wildlife management and conservation. As eagles age, their migration routes become more precise and refined. Most birds tracked for at least two years returned to Arizona in the fall of their hatch year after summer wanderings in the north.

Researchers suggest that young eagles may take advantage of seasonal food abundance, such as salmon spawning, waterfowl nesting, or large mammal carcasses. Further research is needed to confirm this hypothesis.

Threats and the Importance of Conservation

Bald eagles, like many other birds of prey, face numerous dangers in a human-dominated world. One of the birds in the study crossed ten U.S. states and four Canadian provinces before apparently settling in northern California. At the age of four, it died from electrocution—a sadly common cause of death for large raptors. This loss particularly concerned researchers, as it highlights ongoing risks for these birds and the difficulty of measuring emigration as a factor in population dynamics. The eagle’s decision to remain and nest in California could have provided rare insight into how often eagles hatched in Arizona disperse to other regions.

Other threats to young raptors include lead and rodenticide poisoning, collisions with wind turbines, habitat loss, and uncertainty linked to climate change. By studying birds of prey at all life stages—including the exploratory journeys of young individuals—scientists can make informed recommendations about which stopover sites are most critical to protect and which types of infrastructure, such as power lines, can be modified to improve survival rates for eagles and other large raptors.

Future Research Directions

The research team recommends focusing future studies on the consistency of migration routes. As Cappello notes, if stable patterns exist, this will help concentrate conservation efforts on the most frequently used segments of migration paths. The importance of comparing Arizona’s bald eagles with other wild populations migrating north from the southern edge of their range is also emphasized, to better understand the trade-offs, costs, and benefits of the northward migration strategy.